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Dasgupta P, Halder S, Dari D, Nabeel P, Vajja SS, Nandy B. Evolution of a novel female reproductive strategy in Drosophila melanogaster populations subjected to long-term protein restriction. Evolution 2022; 76:1836-1848. [PMID: 35796749 DOI: 10.1111/evo.14560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 05/19/2022] [Indexed: 01/22/2023]
Abstract
Reproductive output is often constrained by availability of macronutrients, especially protein. Long-term protein restriction, therefore, is expected to select for traits maximizing reproduction even under nutritional challenge. We subjected four replicate populations of Drosophila melanogaster to a complete deprivation of yeast supplement, thereby mimicking a protein-restricted ecology. Following 24 generations, compared to their matched controls, females from experimental populations showed increased reproductive output early in life, both in presence and absence of yeast supplement. The observed increase in reproductive output was without associated alterations in egg size, development time, preadult survivorship, body mass at eclosion, and life span of the females. Further, selection was ineffective on lifelong cumulative fecundity. However, females from experiment regime were found to have a significantly faster rate of reproductive senescence following the attainment of the reproductive peak early in life. Therefore, adaptation to yeast deprivation ecology in our study involved a novel reproductive strategy whereby females attained higher reproductive output early in life followed by faster reproductive aging. To the best of our knowledge, this is one of the cleanest demonstrations of optimization of fitness by fine-tuning of reproductive schedule during adaptation to a prolonged nutritional deprivation.
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Affiliation(s)
- Purbasha Dasgupta
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India
| | - Subhasish Halder
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India
| | - Debapriya Dari
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India
| | - Poolakkal Nabeel
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India.,Central University of Kerala, Tejaswini Hills,Periye, Kasaragod, Kerala, 671316, India
| | - Sai Samhitha Vajja
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India.,Current Address: Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhauri, 462066, India
| | - Bodhisatta Nandy
- Department of Biological Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, 760010, India
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2
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Drosophila melanogaster Stress Odorant (dSO) Displays the Characteristics of an Interspecific Alarm Cue. J Chem Ecol 2021; 47:719-731. [PMID: 34402994 DOI: 10.1007/s10886-021-01300-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 07/01/2021] [Accepted: 07/13/2021] [Indexed: 10/20/2022]
Abstract
Organisms depend on visual, auditory, and olfactory cues to signal the presence of danger that could impact survival and reproduction. Drosophila melanogaster emits an olfactory alarm signal, termed the Drosophila stress odorant (dSO), in response to mechanical agitation or electric shock. While it has been shown that conspecifics avoid areas previously occupied by stressed individuals, the contextual underpinnings of the emission of, and response to dSO, have received little attention. Using a binary choice assay, we determined that neither age and sex of emitters, nor the time of the day, affected the emission or avoidance of dSO. However, both sex and mating status affected the response to dSO. We also demonstrated that while D. melanogaster, D. simulans, and D. suzukii, have different dSO profiles, its avoidance was not species-specific. Thus, dSO should not be considered a pheromone but a general alarm signal for Drosophila. However, the response levels to both intra- and inter-specific cues differed between Drosophila species and possible reasons for these differences are discussed.
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3
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Akhund-Zade J, Lall S, Gajda E, Yoon D, Ayroles JF, de Bivort BL. Genetic basis of offspring number-body weight tradeoff in Drosophila melanogaster. G3 (BETHESDA, MD.) 2021; 11:6237891. [PMID: 33871609 PMCID: PMC8496212 DOI: 10.1093/g3journal/jkab129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 04/05/2021] [Indexed: 01/09/2023]
Abstract
Drosophila melanogaster egg production, a proxy for fecundity, is an extensively studied life-history trait with a strong genetic basis. As eggs develop into larvae and adults, space and resource constraints can put pressure on the developing offspring, leading to a decrease in viability, body size, and lifespan. Our goal was to map the genetic basis of offspring number and weight under the restriction of a standard laboratory vial. We screened 143 lines from the Drosophila Genetic Reference Panel for offspring numbers and weights to create an “offspring index” that captured the number vs weight tradeoff. We found 18 genes containing 30 variants associated with variation in the offspring index. Validation of hid, Sox21b, CG8312, and mub candidate genes using gene disruption mutants demonstrated a role in adult stage viability, while mutations in Ih and Rbp increased offspring number and increased weight, respectively. The polygenic basis of offspring number and weight, with many variants of small effect, as well as the involvement of genes with varied functional roles, support the notion of Fisher’s “infinitesimal model” for this life-history trait.
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Affiliation(s)
- Jamilla Akhund-Zade
- Department of Organismic and Evolutionary Biology & Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Shraddha Lall
- Department of Organismic and Evolutionary Biology & Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Erika Gajda
- Department of Organismic and Evolutionary Biology & Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Denise Yoon
- Department of Organismic and Evolutionary Biology & Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Julien F Ayroles
- Department of Ecology and Evolutionary Biology & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ, 08544, USA
| | - Benjamin L de Bivort
- Department of Organismic and Evolutionary Biology & Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
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4
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Turan ZG, Parvizi P, Dönertaş HM, Tung J, Khaitovich P, Somel M. Molecular footprint of Medawar's mutation accumulation process in mammalian aging. Aging Cell 2019; 18:e12965. [PMID: 31062469 PMCID: PMC6612638 DOI: 10.1111/acel.12965] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 02/14/2019] [Accepted: 03/28/2019] [Indexed: 12/20/2022] Open
Abstract
Medawar's mutation accumulation hypothesis explains aging by the declining force of natural selection with age: Slightly deleterious germline mutations expressed in old age can drift to fixation and thereby lead to aging‐related phenotypes. Although widely cited, empirical evidence for this hypothesis has remained limited. Here, we test one of its predictions that genes relatively highly expressed in old adults should be under weaker purifying selection than genes relatively highly expressed in young adults. Combining 66 transcriptome datasets (including 16 tissues from five mammalian species) with sequence conservation estimates across mammals, here we report that the overall conservation level of expressed genes is lower at old age compared to young adulthood. This age‐related decrease in transcriptome conservation (ADICT) is systematically observed in diverse mammalian tissues, including the brain, liver, lung, and artery, but not in others, most notably in the muscle and heart. Where observed, ADICT is driven partly by poorly conserved genes being up‐regulated during aging. In general, the more often a gene is found up‐regulated with age among tissues and species, the lower its evolutionary conservation. Poorly conserved and up‐regulated genes have overlapping functional properties that include responses to age‐associated tissue damage, such as apoptosis and inflammation. Meanwhile, these genes do not appear to be under positive selection. Hence, genes contributing to old age phenotypes are found to harbor an excess of slightly deleterious alleles, at least in certain tissues. This supports the notion that genetic drift shapes aging in multicellular organisms, consistent with Medawar's mutation accumulation hypothesis.
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Affiliation(s)
- Zeliha Gözde Turan
- Department of Biological Sciences Middle East Technical University Ankara Turkey
| | - Poorya Parvizi
- Department of Biological Sciences Middle East Technical University Ankara Turkey
- Usher Institute of Population Health Sciences and Informatics University of Edinburgh Edinburgh UK
| | - Handan Melike Dönertaş
- European Molecular Biology Laboratory, European Bioinformatics Institute EMBL‐EBI Wellcome Trust Genome Campus Cambridge UK
| | - Jenny Tung
- Department of Evolutionary Anthropology Duke University Durham North Carolina
- Department of Biology Duke University Durham North Carolina
- Duke Population Research Institute Duke University Durham North Carolina
| | - Philipp Khaitovich
- Center for Neurobiology and Brain Restoration Skolkovo Institute of Science and Technology Moscow Russia
- CAS Key Laboratory of Computational Biology, CAS‐MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai China
| | - Mehmet Somel
- Department of Biological Sciences Middle East Technical University Ankara Turkey
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5
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Churchill ER, Dytham C, Thom MDF. Differing effects of age and starvation on reproductive performance in Drosophila melanogaster. Sci Rep 2019; 9:2167. [PMID: 30770855 PMCID: PMC6377613 DOI: 10.1038/s41598-019-38843-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 01/10/2019] [Indexed: 02/02/2023] Open
Abstract
Successful reproduction requires the completion of many, often condition-dependent, stages, from mate searching and courtship through to sperm transfer, fertilisation and offspring production. Animals can plastically adjust their investment in each stage according to the physical and social environment, their own condition, their future reproductive potential, and the condition of their partner. Here we manipulate age and condition, through a nutritional challenge early or late in life, of both male and female Drosophila melanogaster and measure the effects on courtship, mating, and fitness when paired with a standardized (unmanipulated) partner. Older males were slower to start courting and mating, and courted at a slower rate, but males were indifferent to female age or condition despite older females laying and hatching fewer eggs. Female condition had a substantial effect on mating acceptance rate, which dropped dramatically after starvation, and particularly recent starvation experience. In contrast, male condition had little effect on any of the components of reproductive performance we measured. Intriguingly, we found no evidence for additive or multiplicative effects of ageing and starvation: the only significant interaction between these variables was on male latency to initiate courtship - older males were slower to start courting unless they had experienced starvation early in life. These results indicate that the immediate costs of mating differ between males and females, and that the sexes differ in their perception of the opportunity cost sustained by refusing a mating opportunity. Our results support the idea that ageing has more wide-ranging impact on reproductive behaviours than does nutritional challenge.
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Affiliation(s)
- Emily R Churchill
- Department of Biology, University of York, York, YO10 5DD, UK
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, PL4 8AA, UK
| | - Calvin Dytham
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Michael D F Thom
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, PL4 8AA, UK.
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6
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Koch RE, Phillips JM, Camus MF, Dowling DK. Maternal age effects on fecundity and offspring egg-to-adult viability are not affected by mitochondrial haplotype. Ecol Evol 2018; 8:10722-10732. [PMID: 30519401 PMCID: PMC6262919 DOI: 10.1002/ece3.4516] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 08/16/2018] [Accepted: 08/17/2018] [Indexed: 01/07/2023] Open
Abstract
While numerous studies have demonstrated that mitochondrial genetic variation can shape organismal phenotype, the level of contribution the mitochondrial genotype makes to life-history phenotype across the life course remains unknown. Furthermore, a clear technical bias has emerged in studies of mitochondrial effects on reproduction, with many studies conducted on males, but few on females. Here, we apply a classic prediction of the evolutionary theory of aging to the mitochondrial genome, predicting the declining force of natural selection with age will have facilitated the accumulation of mtDNA mutations that confer late-life effects on female reproductive performance. This should lead to increased levels of mitochondrial genetic variation on reproduction at later-life stages. We tested this hypothesis using thirteen strains of Drosophila melanogaster that each possessed a different mitochondrial haplotype in an otherwise standard nuclear genetic background. We measured fecundity and egg-to-adult viability of females over five different age classes ranging from early to late life and quantified the survival of females throughout this time period. We found no significant variation across mitochondrial haplotypes for the reproductive traits, and no mitochondrial effect on the slope of decline in these traits with increasing age. However, we observed that flies that died earlier in the experiment experienced steeper declines in the reproductive traits prior to death, and we also identified maternal and grandparental age effects on the measured traits. These results suggest the mitochondrial variation does not make a key contribution to shaping the reproductive performance of females.
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Affiliation(s)
- Rebecca E. Koch
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
| | - James M. Phillips
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
| | - M. Florencia Camus
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
- Department of Genetics, Evolution and EnvironmentUniversity CollegeLondonUK
| | - Damian K. Dowling
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
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7
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Everman ER, Morgan TJ. Antagonistic pleiotropy and mutation accumulation contribute to age-related decline in stress response. Evolution 2018; 72:303-317. [PMID: 29214647 DOI: 10.1111/evo.13408] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 11/10/2017] [Accepted: 11/13/2017] [Indexed: 01/17/2023]
Abstract
As organisms age, the effectiveness of natural selection weakens, leading to age-related decline in fitness-related traits. The evolution of age-related changes associated with senescence is likely influenced by mutation accumulation (MA) and antagonistic pleiotropy (AP). MA predicts that age-related decline in fitness components is driven by age-specific sets of alleles, nonnegative genetic correlations within trait across age, and an increase in the coefficient of genetic variance. AP predicts that age-related decline in a trait is driven by alleles with positive effects on fitness in young individuals and negative effects in old individuals, and is expected to lead to negative genetic correlations within traits across age. We build on these predictions using an association mapping approach to investigate the change in additive effects of SNPs across age and among traits for multiple stress-response fitness-related traits, including cold stress with and without acclimation and starvation resistance. We found support for both MA and AP theories of aging in the age-related decline in stress tolerance. Our study demonstrates that the evolution of age-related decline in stress tolerance is driven by a combination of alleles that have age-specific additive effects, consistent with MA, as well as nonindependent and antagonistic genetic architectures characteristic of AP.
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Affiliation(s)
- Elizabeth R Everman
- Division of Biology, Kansas State University, Manhattan, Kansas 66506
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045
| | - Theodore J Morgan
- Division of Biology, Kansas State University, Manhattan, Kansas 66506
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8
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Dudycha JL, Tessier AJ. NATURAL GENETIC VARIATION OF LIFE SPAN, REPRODUCTION, AND JUVENILE GROWTH IN
DAPHNIA. Evolution 2017; 53:1744-1756. [DOI: 10.1111/j.1558-5646.1999.tb04559.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/1998] [Accepted: 05/26/1999] [Indexed: 11/30/2022]
Affiliation(s)
- Jeffry L. Dudycha
- W. K. Kellogg Biological Station and Department of Zoology Michigan State University 3700 East Gull Lake Drive Hickory Corners Michigan 49060‐9516
| | - Alan J. Tessier
- W. K. Kellogg Biological Station and Department of Zoology Michigan State University 3700 East Gull Lake Drive Hickory Corners Michigan 49060‐9516
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9
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Hughes KA, Leips J. Pleiotropy, constraint, and modularity in the evolution of life histories: insights from genomic analyses. Ann N Y Acad Sci 2017; 1389:76-91. [PMID: 27936291 PMCID: PMC5318229 DOI: 10.1111/nyas.13256] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 08/10/2016] [Accepted: 08/22/2016] [Indexed: 12/20/2022]
Abstract
Multicellular organisms display an enormous range of life history (LH) strategies and present an evolutionary conundrum; despite strong natural selection, LH traits are characterized by high levels of genetic variation. To understand the evolution of life histories and maintenance of this variation, the specific phenotypic effects of segregating alleles and the genetic networks in which they act need to be elucidated. In particular, the extent to which LH evolution is constrained by the pleiotropy of alleles contributing to LH variation is generally unknown. Here, we review recent empirical results that shed light on this question, with an emphasis on studies employing genomic analyses. While genome-scale analyses are increasingly practical and affordable, they face limitations of genetic resolution and statistical power. We describe new research approaches that we believe can produce new insights and evaluate their promise and applicability to different kinds of organisms. Two approaches seem particularly promising: experiments that manipulate selection in multiple dimensions and measure phenotypic and genomic response and analytical approaches that take into account genome-wide associations between markers and phenotypes, rather than applying a traditional marker-by-marker approach.
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Affiliation(s)
- Kimberly A. Hughes
- Department of Biological Science, Florida State University, Tallahassee, Florida
| | - Jeff Leips
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland
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10
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Kim Y, Nam HG, Valenzano DR. The short-lived African turquoise killifish: an emerging experimental model for ageing. Dis Model Mech 2016; 9:115-29. [PMID: 26839399 PMCID: PMC4770150 DOI: 10.1242/dmm.023226] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Human ageing is a fundamental biological process that leads to functional decay, increased risk for various diseases and, ultimately, death. Some of the basic biological mechanisms underlying human ageing are shared with other organisms; thus, animal models have been invaluable in providing key mechanistic and molecular insights into the common bases of biological ageing. In this Review, we briefly summarise the major applications of the most commonly used model organisms adopted in ageing research and highlight their relevance in understanding human ageing. We compare the strengths and limitations of different model organisms and discuss in detail an emerging ageing model, the short-lived African turquoise killifish. We review the recent progress made in using the turquoise killifish to study the biology of ageing and discuss potential future applications of this promising animal model.
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Affiliation(s)
- Yumi Kim
- Max Planck Institute for Biology of Ageing, D50931, Cologne, Germany Department of New Biology, DGIST, 711-873, Daegu, Republic of Korea
| | - Hong Gil Nam
- Department of New Biology, DGIST, 711-873, Daegu, Republic of Korea Center for Plant Aging Research, Institute for Basic Science, 711-873, Daegu, Republic of Korea
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11
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Hayward AD, Moorad J, Regan CE, Berenos C, Pilkington JG, Pemberton JM, Nussey DH. Asynchrony of senescence among phenotypic traits in a wild mammal population. Exp Gerontol 2015; 71:56-68. [PMID: 26277618 PMCID: PMC4661475 DOI: 10.1016/j.exger.2015.08.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 07/14/2015] [Accepted: 08/04/2015] [Indexed: 01/10/2023]
Abstract
The degree to which changes in lifespan are coupled to changes in senescence in different physiological systems and phenotypic traits is a central question in biogerontology. It is underpinned by deeper biological questions about whether or not senescence is a synchronised process, or whether levels of synchrony depend on species or environmental context. Understanding how natural selection shapes patterns of synchrony in senescence across physiological systems and phenotypic traits demands the longitudinal study of many phenotypes under natural conditions. Here, we examine the patterns of age-related variation in late adulthood in a wild population of Soay sheep (Ovis aries) that have been the subject of individual-based monitoring for thirty years. We examined twenty different phenotypic traits in both males and females, encompassing vital rates (survival and fecundity), maternal reproductive performance (offspring birth weight, birth date and survival), male rutting behaviour, home range measures, parasite burdens, and body mass. We initially quantified age-related variation in each trait having controlled for annual variation in the environment, among-individual variation and selective disappearance effects. We then standardised our age-specific trait means and tested whether age trajectories could be meaningfully grouped according to sex or the type of trait. Whilst most traits showed age-related declines in later life, we found striking levels of asynchrony both within and between the sexes. Of particular note, female fecundity and reproductive performance declined with age, but male annual reproductive success did not. We also discovered that whilst home range size and quality decline with age in females, home range size increases with age in males. Our findings highlight the complexity of phenotypic ageing under natural conditions and, along with emerging data from other wild populations and laboratory models, suggest that the long-standing hypothesis within evolutionary biology that fitness-related traits should senesce in a synchronous manner is seriously flawed.
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Affiliation(s)
- Adam D Hayward
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Jacob Moorad
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Charlotte E Regan
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Camillo Berenos
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Jill G Pilkington
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Josephine M Pemberton
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom
| | - Daniel H Nussey
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, United Kingdom.
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12
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Miller PB, Obrik-Uloho OT, Phan MH, Medrano CL, Renier JS, Thayer JL, Wiessner G, Bloch Qazi MC. The song of the old mother: reproductive senescence in female drosophila. Fly (Austin) 2015; 8:127-39. [PMID: 25523082 DOI: 10.4161/19336934.2014.969144] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Among animals with multiple reproductive episodes, changes in adult condition over time can have profound effects on lifetime reproductive fitness and offspring performance. The changes in condition associated with senescence can be particularly acute for females who support reproductive processes from oogenesis through fertilization. The pomace fly Drosophila melanogaster is a well-established model system for exploring the physiology of reproduction and senescence. In this review, we describe how increasing maternal age in Drosophila affects reproductive fitness and offspring performance as well as the genetic foundation of these effects. Describing the processes underlying female reproductive senescence helps us understand diverse phenomena including population demographics, condition-dependent selection, sexual conflict, and transgenerational effects of maternal condition on offspring fitness. Understanding the genetic basis of reproductive senescence clarifies the nature of life-history trade-offs as well as potential ways to augment and/or limit female fertility in a variety of organisms.
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Affiliation(s)
- Paige B Miller
- a Department of Biology ; Gustavus Adolphus College ; St Peter , MN USA
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13
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Carnes MU, Campbell T, Huang W, Butler DG, Carbone MA, Duncan LH, Harbajan SV, King EM, Peterson KR, Weitzel A, Zhou S, Mackay TFC. The Genomic Basis of Postponed Senescence in Drosophila melanogaster. PLoS One 2015; 10:e0138569. [PMID: 26378456 PMCID: PMC4574564 DOI: 10.1371/journal.pone.0138569] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 09/01/2015] [Indexed: 12/30/2022] Open
Abstract
Natural populations harbor considerable genetic variation for lifespan. While evolutionary theory provides general explanations for the existence of this variation, our knowledge of the genes harboring naturally occurring polymorphisms affecting lifespan is limited. Here, we assessed the genetic divergence between five Drosophila melanogaster lines selected for postponed senescence for over 170 generations (O lines) and five lines from the same base population maintained at a two week generation interval for over 850 generations (B lines). On average, O lines live 70% longer than B lines, are more productive at all ages, and have delayed senescence for other traits than reproduction. We performed population sequencing of pools of individuals from all B and O lines and identified 6,394 genetically divergent variants in or near 1,928 genes at a false discovery rate of 0.068. A 2.6 Mb region at the tip of the X chromosome contained many variants fixed for alternative alleles in the two populations, suggestive of a hard selective sweep. We also assessed genome wide gene expression of O and B lines at one and five weeks of age using RNA sequencing and identified genes with significant (false discovery rate < 0.05) effects on gene expression with age, population and the age by population interaction, separately for each sex. We identified transcripts that exhibited the transcriptional signature of postponed senescence and integrated the gene expression and genetic divergence data to identify 98 (175) top candidate genes in females (males) affecting postponed senescence and increased lifespan. While several of these genes have been previously associated with Drosophila lifespan, most are novel and constitute a rich resource for future functional validation.
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Affiliation(s)
- Megan Ulmer Carnes
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Terry Campbell
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Wen Huang
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; Program in Genetics, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Daniel G Butler
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Mary Anna Carbone
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; Program in Genetics, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Laura H Duncan
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Sasha V Harbajan
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Edward M King
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Kara R Peterson
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Alexander Weitzel
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Shanshan Zhou
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; Program in Genetics, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
| | - Trudy F C Mackay
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; Program in Genetics, North Carolina State University, Raleigh, North Carolina, 27695, United States of America; W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, 27695, United States of America
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14
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von Wyschetzki K, Rueppell O, Oettler J, Heinze J. Transcriptomic Signatures Mirror the Lack of the Fecundity/Longevity Trade-Off in Ant Queens. Mol Biol Evol 2015; 32:3173-85. [PMID: 26341296 DOI: 10.1093/molbev/msv186] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Life-history theory predicts a trade-off between reproductive investment and self-maintenance. The negative association between fertility and longevity found throughout multicellular organisms supports this prediction. As an important exception, the reproductives of many eusocial insects (ants, bees, and termites) are simultaneously very long-lived and highly fertile. Here, we examine the proximate basis for this exceptional relationship by comparing whole-body transcriptomes of differently aged queens of the ant Cardiocondyla obscurior. We show that the sets of genes differentially expressed with age significantly overlap with age-related expression changes previously found in female Drosophila melanogaster. We identified several developmental processes, such as the generation of neurons, as common signatures of aging. More generally, however, gene expression in ant queens and flies changes with age mainly in opposite directions. In contrast to flies, reproduction-associated genes were upregulated and genes associated with metabolic processes and muscle contraction were downregulated in old relative to young ant queens. Furthermore, we searched for putative C. obscurior longevity candidates associated with the previously reported lifespan-prolonging effect of mating by comparing the transcriptomes of queens that differed in mating and reproductive status. We found 21 genes, including the putative aging candidate NLaz (an insect homolog of APOD), which were consistently more highly expressed in short-lived, unmated queens than in long-lived, mated queens. Our study provides clear evidence that the alternative regulation of conserved molecular pathways that mediate the interplay among mating, egg laying, and aging underlies the lack of the fecundity/longevity trade-off in ant queens.
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Affiliation(s)
| | - Olav Rueppell
- Department of Biology, University of North Carolina, Greensboro
| | - Jan Oettler
- LS Zoologie/Evolutionsbiologie, Universität Regensburg, Regensburg, Germany
| | - Jürgen Heinze
- LS Zoologie/Evolutionsbiologie, Universität Regensburg, Regensburg, Germany
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15
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Behrman EL, Watson SS, O'Brien KR, Heschel MS, Schmidt PS. Seasonal variation in life history traits in two Drosophila species. J Evol Biol 2015; 28:1691-704. [PMID: 26174167 DOI: 10.1111/jeb.12690] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 06/30/2015] [Accepted: 07/01/2015] [Indexed: 01/16/2023]
Abstract
Seasonal environmental heterogeneity is cyclic, persistent and geographically widespread. In species that reproduce multiple times annually, environmental changes across seasonal time may create different selection regimes that may shape the population ecology and life history adaptation in these species. Here, we investigate how two closely related species of Drosophila in a temperate orchard respond to environmental changes across seasonal time. Natural populations of Drosophila melanogaster and Drosophila simulans were sampled at four timepoints from June through November to assess seasonal change in fundamental aspects of population dynamics as well as life history traits. D. melanogaster exhibit pronounced change across seasonal time: early in the season, the population is inferred to be uniformly young and potentially represents the early generation following overwintering survivorship. D. melanogaster isofemale lines derived from the early population and reared in a common garden are characterized by high tolerance to a variety of stressors as well as a fast rate of development in the laboratory environment that declines across seasonal time. In contrast, wild D. simulans populations were inferred to be consistently heterogeneous in age distribution across seasonal collections; only starvation tolerance changed predictably over seasonal time in a parallel manner as in D. melanogaster. These results suggest fundamental differences in population and evolutionary dynamics between these two taxa associated with seasonal heterogeneity in environmental parameters and associated selection pressures.
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Affiliation(s)
- E L Behrman
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - S S Watson
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - K R O'Brien
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.,School of Biological Sciences, University of Nebraska, Lincoln, NE, USA
| | - M S Heschel
- Department of Organismal Biology & Ecology, Colorado College, Colorado Springs, CO, USA
| | - P S Schmidt
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
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16
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Fisher DN, David M, Tregenza T, Rodríguez-Muñoz R. Dynamics of among-individual behavioral variation over adult lifespan in a wild insect. Behav Ecol 2015; 26:975-985. [PMID: 26167097 PMCID: PMC4495759 DOI: 10.1093/beheco/arv048] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 03/18/2015] [Accepted: 03/19/2015] [Indexed: 11/13/2022] Open
Abstract
Investigating patterns of among and within-individual trait variation in populations is essential to understanding how selection shapes phenotypes. Behavior is often the most flexible aspect of the phenotype, and to understand how it is affected by selection, we need to examine how consistent individuals are. However, it is not well understood whether among-individual differences tend to remain consistent over lifetimes, or whether the behavior of individuals relative to one another varies over time. We examined the dynamics of 4 behavioral traits (tendency to leave a refuge, shyness, activity, and exploration) in a wild population of field crickets (Gryllus campestris). We tagged individuals and then temporarily removed them from their natural environment and tested them under laboratory conditions. All 4 traits showed among-individual variance in mean levels of expression across the adult lifespan, but no significant differences in how rapidly expression changed with age. For all traits, among-individual variance increased as individuals got older. Our findings reveal seldom examined changes in variance components over the adult lifetime of wild individuals. Such changes will have important implications for the relationship between behavioral traits, life-histories, and fitness and the consequences of selection on wild individuals.
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Affiliation(s)
- David N Fisher
- Centre for Ecology and Conservation, University of Exeter , Treliever Road, Penryn TR109FE , UK and
| | - Morgan David
- Centre for Ecology and Conservation, University of Exeter , Treliever Road, Penryn TR109FE , UK and ; Department of Biology-Ethology, University of Antwerp , Drie Eiken Campus, Universiteitsplein 1, 2610 Wilrijk (Antwerpen) , Belgium
| | - Tom Tregenza
- Centre for Ecology and Conservation, University of Exeter , Treliever Road, Penryn TR109FE , UK and
| | - Rolando Rodríguez-Muñoz
- Centre for Ecology and Conservation, University of Exeter , Treliever Road, Penryn TR109FE , UK and
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17
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Maklakov AA, Rowe L, Friberg U. Why organisms age: Evolution of senescence under positive pleiotropy? Bioessays 2015; 37:802-7. [DOI: 10.1002/bies.201500025] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Alexei A. Maklakov
- Department of Animal Ecology; Evolutionary Biology Centre; Ageing Research Group; Uppsala University; Uppsala Sweden
| | - Locke Rowe
- Department of Ecology and Evolutionary Biology; University of Toronto; Toronto ON Canada
| | - Urban Friberg
- Department of Evolutionary Biology; Evolutionary Biology Centre; Ageing Research Group; Uppsala University; Uppsala Sweden
- IFM Biology; AVIAN Behavioural Genomics and Physiology Group; Linköping University; Linköping Sweden
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18
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Durham MF, Magwire MM, Stone EA, Leips J. Genome-wide analysis in Drosophila reveals age-specific effects of SNPs on fitness traits. Nat Commun 2014; 5:4338. [PMID: 25000897 DOI: 10.1038/ncomms5338] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 06/09/2014] [Indexed: 12/13/2022] Open
Abstract
Most organisms exhibit senescence; a decline in physiological function with age. In nature, rates of senescence vary extensively among individuals and this variation has a significant genetic component; however, we know little about the genes underlying senescence. Here we show the first evidence that individual alleles influence fecundity in an age-specific manner and so the genetic basis of natural variation in fecundity changes dramatically with age. We complete a genome-wide association to identify single-nucleotide polymorphisms (SNPs) affecting lifespan and age-specific fecundity using the Drosophila melanogaster Genetic Reference Panel. We identify 1,031 SNPs affecting fecundity and 52 influencing lifespan. Only one SNP is associated with both early- and late-age fecundity. The age-specific effect of candidate genes on fecundity is validated using RNA interference. In addition, there is a dramatic increase in the number of SNPs influencing fecundity with age. This result provides support for the mutation accumulation theory of aging.
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Affiliation(s)
- Mary F Durham
- Department of Biological Sciences, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA
| | - Michael M Magwire
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Eric A Stone
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Jeff Leips
- Department of Biological Sciences, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA
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Varma V, Kannan NN, Sharma VK. Selection for narrow gate of emergence results in correlated sex-specific changes in life history of Drosophila melanogaster. Biol Open 2014; 3:606-13. [PMID: 24950968 PMCID: PMC4154297 DOI: 10.1242/bio.20147906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Since the ability to time rhythmic behaviours in accordance with cyclic environments is likely to confer adaptive advantage to organisms, the underlying clocks are believed to be selected for stability in timekeeping over evolutionary time scales. Here we report the results of a study aimed at assessing fitness consequences of a long-term laboratory selection for tighter circadian organisation using fruit fly Drosophila melanogaster populations. We selected flies emerging in a narrow window of 1 h in the morning for several generations and assayed their life history traits such as pre-adult development time, survivorship, adult lifespan and lifetime fecundity. We chose flies emerging during the selection window (in the morning) and another window (in the evening) to represent adaptive and non-adaptive phenotypes, respectively, and examined the correlation of emergence time with adult fitness traits. Adult lifespan of males from the selected populations does not differ from the controls, whereas females from the selected populations have significantly shorter lifespan and produce more eggs during their mid-life compared to the controls. Although there is no difference in the lifespan of males of the selected populations, whether they emerge in morning or evening window, morning emerging females live slightly shorter and lay more eggs during the mid-life stage compared to those emerging in the evening. Interestingly, such a time of emergence dependent difference in fitness is not seen in flies from the control populations. These results, therefore, suggest reduced lifespan and enhanced mid-life reproductive output in females selected for narrow gate of emergence, and a sex-dependent genetic correlation between the timing of emergence and key fitness traits in these populations.
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Affiliation(s)
- Vishwanath Varma
- Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
| | - Nisha N Kannan
- Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
| | - Vijay Kumar Sharma
- Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
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20
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Kimber CM, Chippindale AK. Mutation, condition, and the maintenance of extended lifespan in Drosophila. Curr Biol 2013; 23:2283-2287. [PMID: 24210612 DOI: 10.1016/j.cub.2013.09.049] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 09/18/2013] [Accepted: 09/23/2013] [Indexed: 10/26/2022]
Abstract
The evolutionary theory of aging predicts that longevity will decline via drift or age-specific tradeoffs when selection favors early life fitness. Many Drosophila melanogaster populations continually terminated at young adult ages retain surprisingly long postselection lifespans. We compiled three decades of longevity data from the Ives population, demonstrating that postselective longevity was both substantial (30 days) and temporally stable over this period. Recently, alleles with positive pleiotropic effects between adjacent ages, particularly those affecting overall condition, have been integrated into the theory and may explain the extended longevity observed. We experimentally tested this hypothesis by isolating 20 hemiclones from Ives and allowing spontaneous mutations to accumulate (MA) for 35 generations. Fitness and longevity were positively genetically correlated in control females, and both traits declined due to MA. Crucially, MA induced a strong positive genetic correlation between the traits in both sexes, implying that mutations with early-life impacts also reduce late-life survival. Our results suggest that extended postreproductive longevity is actively maintained by selection for early-life fitness via positive pleiotropy and is not a merely a byproduct of exhaustion of genetic variation or weak drift. Thus mutation-selection balance for early fitness may govern variance in longevity in this system: a balance struck remarkably long after selection for continued survival ceases.
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21
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Kriete A. Robustness and aging--a systems-level perspective. Biosystems 2013; 112:37-48. [PMID: 23562399 DOI: 10.1016/j.biosystems.2013.03.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/11/2013] [Accepted: 03/15/2013] [Indexed: 12/24/2022]
Abstract
The theory of robustness describes a system level property of evolutionary systems, which predicts tradeoffs of great interest for the systems biology of aging, such as accumulation of non-heritable damage, occurrence of fragilities and limitations in performance, optimized allocation of restricted resources and confined redundancies. According to the robustness paradigm cells and organisms evolved into a state of highly optimized tolerance (HOT), which provides robustness to common perturbations, but causes tradeoffs generally characterized as "robust yet fragile". This raises the question whether the ultimate cause of aging is more than a lack of adaptation, but an inherent fragility of complex evolutionary systems. Since robustness connects to evolutionary designs, consideration of this theory provides a deeper connection between evolutionary aspects of aging, mathematical models and experimental data. In this review several mechanisms influential for aging are re-evaluated in support of robustness tradeoffs. This includes asymmetric cell division improving performance and specialization with limited capacities to prevent and repair age-related damage, as well as feedback control mechanisms optimized to respond to acute stressors, but unable to halt nor revert aging. Improvement in robustness by increasing efficiencies through cellular redundancies in larger organisms alleviates some of the damaging effects of cellular specialization, which can be expressed in allometric relationships. The introduction of the robustness paradigm offers unique insights for aging research and provides novel opportunities for systems biology endeavors.
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Affiliation(s)
- Andres Kriete
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Bossone Research Center, 3141 Chestnut St., Philadelphia, PA 19104, USA.
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22
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Kaczmarczyk AN, Kopp A. Germline stem cell maintenance as a proximate mechanism of life-history trade-offs? Drosophila selected for prolonged fecundity have a slower rate of germline stem cell loss. Bioessays 2011; 33:5-12. [PMID: 21120852 DOI: 10.1002/bies.201000085] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We suggest that the commonly observed trade-offs between early- and late-life reproduction may be mediated by genetic variation in germline stem cell maintenance. Stem cell biology provides a natural framework and experimental methods for understanding the mechanistic basis of life-history evolution. At the same time, natural variation in life-history strategies can serve as a powerful tool for identifying the genes and molecular pathways involved in the maintenance of stem cells in aging adults. We illustrate the connections between life-history and stem cells with examples drawn primarily from Drosophila melanogaster and Caenorhabditis elegans, and suggest a number of testable hypotheses and avenues for future investigation that can be addressed with existing models and tools.
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23
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24
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Magwire MM, Yamamoto A, Carbone MA, Roshina NV, Symonenko AV, Pasyukova EG, Morozova TV, Mackay TFC. Quantitative and molecular genetic analyses of mutations increasing Drosophila life span. PLoS Genet 2010; 6:e1001037. [PMID: 20686706 PMCID: PMC2912381 DOI: 10.1371/journal.pgen.1001037] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 06/23/2010] [Indexed: 01/21/2023] Open
Abstract
Understanding the genetic and environmental factors that affect variation in life span and senescence is of major interest for human health and evolutionary biology. Multiple mechanisms affect longevity, many of which are conserved across species, but the genetic networks underlying each mechanism and cross-talk between networks are unknown. We report the results of a screen for mutations affecting Drosophila life span. One third of the 1,332 homozygous P-element insertion lines assessed had quantitative effects on life span; mutations reducing life span were twice as common as mutations increasing life span. We confirmed 58 mutations with increased longevity, only one of which is in a gene previously associated with life span. The effects of the mutations increasing life span were highly sex-specific, with a trend towards opposite effects in males and females. Mutations in the same gene were associated with both increased and decreased life span, depending on the location and orientation of the P-element insertion, and genetic background. We observed substantial--and sex-specific--epistasis among a sample of ten mutations with increased life span. All mutations increasing life span had at least one deleterious pleiotropic effect on stress resistance or general health, with different patterns of pleiotropy for males and females. Whole-genome transcript profiles of seven of the mutant lines and the wild type revealed 4,488 differentially expressed transcripts, 553 of which were common to four or more of the mutant lines, which include genes previously associated with life span and novel genes implicated by this study. Therefore longevity has a large mutational target size; genes affecting life span have variable allelic effects; alleles affecting life span exhibit antagonistic pleiotropy and form epistatic networks; and sex-specific mutational effects are ubiquitous. Comparison of transcript profiles of long-lived mutations and the control line reveals a transcriptional signature of increased life span.
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Affiliation(s)
- Michael M Magwire
- Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, United States of America
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25
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Mackay TFC. Mutations and quantitative genetic variation: lessons from Drosophila. Philos Trans R Soc Lond B Biol Sci 2010; 365:1229-39. [PMID: 20308098 DOI: 10.1098/rstb.2009.0315] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A central issue in evolutionary quantitative genetics is to understand how genetic variation for quantitative traits is maintained in natural populations. Estimates of genetic variation and of genetic correlations and pleiotropy among multiple traits, inbreeding depression, mutation rates for fitness and quantitative traits and of the strength and nature of selection are all required to evaluate theoretical models of the maintenance of genetic variation. Studies in Drosophila melanogaster have shown that a substantial fraction of segregating variation for fitness-related traits in Drosophila is due to rare deleterious alleles maintained by mutation-selection balance, with a smaller but significant fraction attributable to intermediate frequency alleles maintained by alleles with antagonistic pleiotropic effects, and late-age-specific effects. However, the nature of segregating variation for traits under stabilizing selection is less clear and requires more detailed knowledge of the loci, mutation rates, allelic effects and frequencies of molecular polymorphisms affecting variation in suites of pleiotropically connected traits. Recent studies in D. melanogaster have revealed unexpectedly complex genetic architectures of many quantitative traits, with large numbers of pleiotropic genes and alleles with sex-, environment- and genetic background-specific effects. Future genome wide association analyses of many quantitative traits on a common panel of fully sequenced Drosophila strains will provide much needed empirical data on the molecular genetic basis of quantitative traits.
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Affiliation(s)
- Trudy F C Mackay
- Department of Genetics, W. M. Keck Center for Behavioral Biology, North Carolina State University, , Campus Box 7614, Raleigh, NC 27697, USA.
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26
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Hughes KA. Mutation and the evolution of ageing: from biometrics to system genetics. Philos Trans R Soc Lond B Biol Sci 2010; 365:1273-9. [PMID: 20308103 DOI: 10.1098/rstb.2009.0265] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
A notable success for evolutionary genetics during the past century was to generate a coherent, quantitative explanation for an apparent evolutionary paradox: the tendency for multicellular organisms to show declining fitness with age (senescence, often referred to simply as 'ageing'). This general theory is now widely accepted and explains most of the features of senescence that are observed in natural and laboratory populations, but specific instantiations of that theory have been more controversial. To date, most of the empirical tests of these models have relied on data generated from biometric experiments. Modern population genetics and genomics provide new, and probably more powerful, ways to test ideas that are still controversial more than half a century after the original theory was developed. System-genetic experiments have the potential to address both evolutionary and mechanistic questions about ageing by identifying causal loci and the genetic networks with which they interact. Both the biometrical approaches and the newer approaches are reviewed here, with an emphasis on the challenges and limitations that each method faces.
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Affiliation(s)
- Kimberly A Hughes
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA.
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27
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Markert JA, Champlin DM, Gutjahr-Gobell R, Grear JS, Kuhn A, McGreevy TJ, Roth A, Bagley MJ, Nacci DE. Population genetic diversity and fitness in multiple environments. BMC Evol Biol 2010; 10:205. [PMID: 20609254 PMCID: PMC2927917 DOI: 10.1186/1471-2148-10-205] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 07/07/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND When a large number of alleles are lost from a population, increases in individual homozygosity may reduce individual fitness through inbreeding depression. Modest losses of allelic diversity may also negatively impact long-term population viability by reducing the capacity of populations to adapt to altered environments. However, it is not clear how much genetic diversity within populations may be lost before populations are put at significant risk. Development of tools to evaluate this relationship would be a valuable contribution to conservation biology. To address these issues, we have created an experimental system that uses laboratory populations of an estuarine crustacean, Americamysis bahia with experimentally manipulated levels of genetic diversity. We created replicate cultures with five distinct levels of genetic diversity and monitored them for 16 weeks in both permissive (ambient seawater) and stressful conditions (diluted seawater). The relationship between molecular genetic diversity at presumptive neutral loci and population vulnerability was assessed by AFLP analysis. RESULTS Populations with very low genetic diversity demonstrated reduced fitness relative to high diversity populations even under permissive conditions. Population performance decreased in the stressful environment for all levels of genetic diversity relative to performance in the permissive environment. Twenty percent of the lowest diversity populations went extinct before the end of the study in permissive conditions, whereas 73% of the low diversity lines went extinct in the stressful environment. All high genetic diversity populations persisted for the duration of the study, although population sizes and reproduction were reduced under stressful environmental conditions. Levels of fitness varied more among replicate low diversity populations than among replicate populations with high genetic diversity. There was a significant correlation between AFLP diversity and population fitness overall; however, AFLP markers performed poorly at detecting modest but consequential losses of genetic diversity. High diversity lines in the stressful environment showed some evidence of relative improvement as the experiment progressed while the low diversity lines did not. CONCLUSIONS The combined effects of reduced average fitness and increased variability contributed to increased extinction rates for very low diversity populations. More modest losses of genetic diversity resulted in measurable decreases in population fitness; AFLP markers did not always detect these losses. However when AFLP markers indicated lost genetic diversity, these losses were associated with reduced population fitness.
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Affiliation(s)
- Jeffrey A Markert
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
- Molecular Ecology Research Branch, Ecological Exposure Research Division, U.S. Environmental Protection Agency, 26 Martin Luther King Dr., Cincinnati OH 45268, USA
- c/o U.S. Geological Survey, San Diego Field Station, Western Ecology Research Center, 4165 Spruance Rd., San Diego, CA 92101, USA
| | - Denise M Champlin
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
| | - Ruth Gutjahr-Gobell
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
| | - Jason S Grear
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
| | - Anne Kuhn
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
| | - Thomas J McGreevy
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
- Department of Natural Resources Science, Coastal Institute, University of Rhode Island, 1 Greenhouse Rd., Kingston RI 02881, USA
| | - Annette Roth
- Molecular Ecology Research Branch, Ecological Exposure Research Division, U.S. Environmental Protection Agency, 26 Martin Luther King Dr., Cincinnati OH 45268, USA
| | - Mark J Bagley
- Molecular Ecology Research Branch, Ecological Exposure Research Division, U.S. Environmental Protection Agency, 26 Martin Luther King Dr., Cincinnati OH 45268, USA
| | - Diane E Nacci
- Population Ecology Branch, Atlantic Ecology Division, U.S. Environmental Protection Agency, 27 Tarzwell Dr., Narragansett RI, USA
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28
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PAABY ANNALISEB, BLACKET MARKJ, HOFFMANN ARYA, SCHMIDT PAULS. Identification of a candidate adaptive polymorphism forDrosophilalife history by parallel independent clines on two continents. Mol Ecol 2010; 19:760-74. [DOI: 10.1111/j.1365-294x.2009.04508.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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29
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MOORAD JA, HALL DW. Age-dependent mutational effects curtail the evolution of senescence by antagonistic pleiotropy. J Evol Biol 2009; 22:2409-19. [DOI: 10.1111/j.1420-9101.2009.01849.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Flatt T, Schmidt PS. Integrating evolutionary and molecular genetics of aging. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1790:951-62. [PMID: 19619612 PMCID: PMC2972575 DOI: 10.1016/j.bbagen.2009.07.010] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Revised: 07/07/2009] [Accepted: 07/10/2009] [Indexed: 12/25/2022]
Abstract
Aging or senescence is an age-dependent decline in physiological function, demographically manifest as decreased survival and fecundity with increasing age. Since aging is disadvantageous it should not evolve by natural selection. So why do organisms age and die? In the 1940s and 1950s evolutionary geneticists resolved this paradox by positing that aging evolves because selection is inefficient at maintaining function late in life. By the 1980s and 1990s this evolutionary theory of aging had received firm empirical support, but little was known about the mechanisms of aging. Around the same time biologists began to apply the tools of molecular genetics to aging and successfully identified mutations that affect longevity. Today, the molecular genetics of aging is a burgeoning field, but progress in evolutionary genetics of aging has largely stalled. Here we argue that some of the most exciting and unresolved questions about aging require an integration of molecular and evolutionary approaches. Is aging a universal process? Why do species age at different rates? Are the mechanisms of aging conserved or lineage-specific? Are longevity genes identified in the laboratory under selection in natural populations? What is the genetic basis of plasticity in aging in response to environmental cues and is this plasticity adaptive? What are the mechanisms underlying trade-offs between early fitness traits and life span? To answer these questions evolutionary biologists must adopt the tools of molecular biology, while molecular biologists must put their experiments into an evolutionary framework. The time is ripe for a synthesis of molecular biogerontology and the evolutionary biology of aging.
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Affiliation(s)
- Thomas Flatt
- Institut für Populationsgenetik, Veterinärmedizinische Universität Wien, Josef Baumann Gasse 1, A-1210 Wien, Austria
| | - Paul S. Schmidt
- University of Pennsylvania, Department of Biology, 433 South University Avenue, Philadelphia, PA 19104-6018, USA.
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Mitteldorf J, Pepper J. Senescence as an adaptation to limit the spread of disease. J Theor Biol 2009; 260:186-95. [DOI: 10.1016/j.jtbi.2009.05.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 04/07/2009] [Accepted: 05/20/2009] [Indexed: 10/20/2022]
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32
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Zajitschek F, Bonduriansky R, Zajitschek S, Brooks R. Sexual Dimorphism in Life History: Age, Survival, and Reproduction in Male and Female Field CricketsTeleogryllus commodusunder Seminatural Conditions. Am Nat 2009; 173:792-802. [DOI: 10.1086/598486] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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33
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DOWLING DK, MAKLAKOV AA, FRIBERG U, HAILER F. Applying the genetic theories of ageing to the cytoplasm: cytoplasmic genetic covariation for fitness and lifespan. J Evol Biol 2009; 22:818-27. [DOI: 10.1111/j.1420-9101.2009.01692.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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34
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Moorad JA, Promislow DEL. What can genetic variation tell us about the evolution of senescence? Proc Biol Sci 2009; 276:2271-8. [PMID: 19324735 DOI: 10.1098/rspb.2009.0183] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Quantitative genetic approaches have been developed that allow researchers to determine which of two mechanisms, mutation accumulation (MA) or antagonistic pleiotropy (AP), best explain observed variation in patterns of senescence using classical quantitative genetic techniques. These include the creation of mutation accumulation lines, artificial selection experiments and the partitioning of genetic variances across age classes. This last strategy has received the lion's share of empirical attention. Models predict that inbreeding depression (ID), dominance variance and the variance among inbred line means will all increase with age under MA but not under those forms of AP that generate marginal overdominance. Here, we show that these measures are not, in fact, diagnostic of MA versus AP. In particular, the assumptions about the value of genetic parameters in existing AP models may be rather narrow, and often violated in reality. We argue that whenever ageing-related AP loci contribute to segregating genetic variation, polymorphism at these loci will be enhanced by genetic effects that will also cause ID and dominance variance to increase with age, effects also expected under the MA model of senescence. We suggest that the tests that seek to identify the relative contributions of AP and MA to the evolution of ageing by partitioning genetic variance components are likely to be too conservative to be of general value.
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Affiliation(s)
- Jacob A Moorad
- Department of Genetics, University of Georgia, Athens, GA 30602, USA.
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35
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Bilde T, Friberg U, Maklakov AA, Fry JD, Arnqvist G. The genetic architecture of fitness in a seed beetle: assessing the potential for indirect genetic benefits of female choice. BMC Evol Biol 2008; 8:295. [PMID: 18950531 PMCID: PMC2596129 DOI: 10.1186/1471-2148-8-295] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 10/26/2008] [Indexed: 11/16/2022] Open
Abstract
Background Quantifying the amount of standing genetic variation in fitness represents an empirical challenge. Unfortunately, the shortage of detailed studies of the genetic architecture of fitness has hampered progress in several domains of evolutionary biology. One such area is the study of sexual selection. In particular, the evolution of adaptive female choice by indirect genetic benefits relies on the presence of genetic variation for fitness. Female choice by genetic benefits fall broadly into good genes (additive) models and compatibility (non-additive) models where the strength of selection is dictated by the genetic architecture of fitness. To characterize the genetic architecture of fitness, we employed a quantitative genetic design (the diallel cross) in a population of the seed beetle Callosobruchus maculatus, which is known to exhibit post-copulatory female choice. From reciprocal crosses of inbred lines, we assayed egg production, egg-to-adult survival, and lifetime offspring production of the outbred F1 daughters (F1 productivity). Results We used the bio model to estimate six components of genetic and environmental variance in fitness. We found sizeable additive and non-additive genetic variance in F1 productivity, but lower genetic variance in egg-to-adult survival, which was strongly influenced by maternal and paternal effects. Conclusion Our results show that, in order to gain a relevant understanding of the genetic architecture of fitness, measures of offspring fitness should be inclusive and should include quantifications of offspring reproductive success. We note that our estimate of additive genetic variance in F1 productivity (CVA = 14%) is sufficient to generate indirect selection on female choice. However, our results also show that the major determinant of offspring fitness is the genetic interaction between parental genomes, as indicated by large amounts of non-additive genetic variance (dominance and/or epistasis) for F1 productivity. We discuss the processes that may maintain additive and non-additive genetic variance for fitness and how these relate to indirect selection for female choice.
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Affiliation(s)
- T Bilde
- Animal Ecology/Department of Ecology and Evolution, Evolutionary Biology Centre, University of Uppsala, Uppsala SE-753 32, Sweden.
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36
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Pettay JE, Charmantier A, Wilson AJ, Lummaa V. AGE-SPECIFIC GENETIC AND MATERNAL EFFECTS IN FECUNDITY OF PREINDUSTRIAL FINNISH WOMEN. Evolution 2008; 62:2297-304. [DOI: 10.1111/j.1558-5646.2008.00452.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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37
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Abstract
Laboratory experiments show us that the deleterious character of accumulated novel age-specific mutations is reduced and made less variable with increased age. While theories of aging predict that the frequency of deleterious mutations at mutation-selection equilibrium will increase with the mutation's age of effect, they do not account for these age-related changes in the distribution of de novo mutational effects. Furthermore, no model predicts why this dependence of mutational effects upon age exists. Because the nature of mutational distributions plays a critical role in shaping patterns of senescence, we need to develop aging theory that explains and incorporates these effects. Here we propose a model that explains the age dependency of mutational effects by extending Fisher's geometrical model of adaptation to include a temporal dimension. Using a combination of simple analytical arguments and simulations, we show that our model predicts age-specific mutational distributions that are consistent with observations from mutation-accumulation experiments. Simulations show us that these age-specific mutational effects may generate patterns of senescence at mutation-selection equilibrium that are consistent with observed demographic patterns that are otherwise difficult to explain.
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38
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Schmidt PS, Paaby AB. REPRODUCTIVE DIAPAUSE AND LIFE-HISTORY CLINES IN NORTH AMERICAN POPULATIONS OF DROSOPHILA MELANOGASTER. Evolution 2008; 62:1204-15. [PMID: 18298646 DOI: 10.1111/j.1558-5646.2008.00351.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Paul S Schmidt
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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39
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Rose MR, Rauser CL, Benford G, Matos M, Mueller LD. Hamilton's forces of natural selection after forty years. Evolution 2007; 61:1265-76. [PMID: 17542838 DOI: 10.1111/j.1558-5646.2007.00120.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In 1966, William D. Hamilton published a landmark paper in evolutionary biology: "The Moulding of Senescence by Natural Selection." It is now apparent that this article is as important as his better-known 1964 articles on kin selection. Not only did the 1966 article explain aging, it also supplied the basic scaling forces for natural selection over the entire life history. Like the Lorentz transformations of relativistic physics, Hamilton's Forces of Natural Selection provide an overarching framework for understanding the power of natural selection at early ages, the existence of aging, the timing of aging, the cessation of aging, and the timing of the cessation of aging. His twin Forces show that natural selection shapes survival and fecundity in different ways, so their evolution can be somewhat distinct. Hamilton's Forces also define the context in which genetic variation is shaped. The Forces of Natural Selection are readily manipulable using experimental evolution, allowing the deceleration or acceleration of aging, and the shifting of the transition ages between development, aging, and late life. For these reasons, evolutionary research on the demographic features of life history should be referred to as "Hamiltonian."
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Affiliation(s)
- Michael R Rose
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525, USA.
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40
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Reynolds RM, Temiyasathit S, Reedy MM, Ruedi EA, Drnevich JM, Leips J, Hughes KA. Age specificity of inbreeding load in Drosophila melanogaster and implications for the evolution of late-life mortality plateaus. Genetics 2007; 177:587-95. [PMID: 17660577 PMCID: PMC2013709 DOI: 10.1534/genetics.106.070078] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Current evolutionary theories explain the origin of aging as a byproduct of the decline in the force of natural selection with age. These theories seem inconsistent with the well-documented occurrence of late-life mortality plateaus, since under traditional evolutionary models mortality rates should increase monotonically after sexual maturity. However, the equilibrium frequencies of deleterious alleles affecting late life are lower than predicted under traditional models, and thus evolutionary models can accommodate mortality plateaus if deleterious alleles are allowed to have effects spanning a range of neighboring age classes. Here we test the degree of age specificity of segregating alleles affecting fitness in Drosophila melanogaster. We assessed age specificity by measuring the homozygous fitness effects of segregating alleles across the adult life span and calculated genetic correlations of these effects across age classes. For both males and females, we found that allelic effects are age specific with effects extending over 1-2 weeks across all age classes, consistent with modified mutation-accumulation theory. These results indicate that a modified mutation-accumulation theory can both explain the origin of senescence and predict late-life mortality plateaus.
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Affiliation(s)
- Rose M Reynolds
- Program in Ecology and Evolutionary Biology, University of Illinois, Urbana-Champaign, Illinois 61801, USA.
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41
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Borash DJ, Rose MR, Mueller LD. Mutation accumulation affects male virility in Drosophila selected for later reproduction. Physiol Biochem Zool 2007; 80:461-72. [PMID: 17717809 DOI: 10.1086/520127] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2007] [Indexed: 11/03/2022]
Abstract
An intensive study of longevity, female fecundity, and male reproductive behavior in Drosophila melanogaster was undertaken in order to establish whether late-life fitness characters in short-lived populations might be affected by the increase in deleterious alleles due to random genetic drift. We also sought to determine whether selection for late-life fertility could eliminate alleles that produce a decline in later fitness components in short-lived populations, as predicted by the mutation accumulation hypothesis for the evolution of aging. These experiments employed long-lived (O) populations, short-lived (B) populations, and hybrids made from crosses of independent lines from within the O and B populations. No detectable longevity differences were seen between hybrid B males and females and purebred B males and females. Reproduction in aged B purebred females was significantly less than in hybrid females at 3 wk of age only. A full diallel cross of the five replicate B lines showed a steady increase in hybrid male reproductive performance after the first week of adult life, relative to the parental lines. A full diallel cross of the five replicate O lines revealed no significant increase in hybrid O age-specific male reproductive success compared with the purebred O lines when assayed over the first 5 wk of adult life. The results on male reproductive behavior are consistent with the idea that relaxed age-specific selection in the B populations has been accompanied by an increase in deleterious, recessive traits that exhibit age-specific expression. Consequently, we conclude that a mutation accumulation process has been at least partly responsible for the age-specific decline in male B virility relative to that of the O populations.
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Affiliation(s)
- Daniel J Borash
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697-2525, USA.
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42
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Ye J, Cui X, Loraine A, Bynum K, Kim NC, White G, De Luca M, Garfinkel MD, Lu X, Ruden DM. Methods for nutrigenomics and longevity studies in Drosophila: effects of diets high in sucrose, palmitic acid, soy, or beef. Methods Mol Biol 2007; 371:111-41. [PMID: 17634578 DOI: 10.1007/978-1-59745-361-5_10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Nutrigenomics is the study of gene-nutrient interactions and how they affect the health and metabolism of an organism. Combining nutrigenomics with longevity studies is a natural extension and promises to help identify mechanisms whereby nutrients affect the aging process, life span, and, with the incorporation of age-dependent functional measures, health span. The topics we discuss in this chapter are genetic techniques, dietary manipulations, metabolic studies, and microarray analysis methods to investigate how nutrition affects gene expression, life span, triglyceride levels, total protein levels, and live weight in Drosophila. To better illustrate nutrigenomic techniques, we analyzed Drosophila larvae or adults fed control diets (high sucrose) and compared these with larvae or adults fed diets high in the saturated fat palmitic acid, soy, or 95% lean ground beef. The main results of these studies are, surprisingly, that triglyceride and total protein levels are significantly decreased by the beef diet in all adults, and total protein levels are significantly increased in male flies fed the soy diet. Furthermore, and less surprisingly, we found that all three experimental diets significantly decreased longevity and increased the length of time to develop from egg to adult. We also describe preliminary microarray results with adult flies fed the different diets, which suggest that only about 2-3% of the approx 18,000 genes have significantly altered mRNA expression levels compared with flies fed a control sucrose diet. The significance of these results and other types of nutrigenomics and longevity analyses is discussed.
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Affiliation(s)
- Jiatao Ye
- Department of Environmental Health Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
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43
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Hughes SE, Evason K, Xiong C, Kornfeld K. Genetic and pharmacological factors that influence reproductive aging in nematodes. PLoS Genet 2006; 3:e25. [PMID: 17305431 PMCID: PMC1797816 DOI: 10.1371/journal.pgen.0030025] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 12/27/2006] [Indexed: 11/19/2022] Open
Abstract
Age-related degenerative changes in the reproductive system are an important aspect of aging, because reproductive success is the major determinant of evolutionary fitness. Caenorhabditis elegans is a prominent organism for studies of somatic aging, since many factors that extend adult lifespan have been identified. However, mechanisms that control reproductive aging in nematodes or other animals are not well characterized. To use C. elegans to measure reproductive aging, we analyzed mated hermaphrodites that do not become sperm depleted and monitored the duration and level of progeny production. Mated hermaphrodites display a decline of progeny production that culminates in reproductive cessation before the end of the lifespan, demonstrating that hermaphrodites undergo reproductive aging. To identify factors that influence reproductive aging, we analyzed genetic, environmental, and pharmacological factors that extend lifespan. Dietary restriction and reduced insulin/insulin-like growth factor signaling delayed reproductive aging, indicating that nutritional status and a signaling pathway that responds to environmental stress influence reproductive aging. Cold temperature delayed reproductive aging. The anticonvulsant medicine ethosuximide, which affects neural activity, delayed reproductive aging, indicating that neural activity can influence reproductive aging. Some of these factors decrease early progeny production, but there is no consistent relationship between early progeny production and reproductive aging in strains with an extended lifespan. To directly examine the effects of early progeny production on reproductive aging, we used sperm availability to modulate the level of early reproduction. Early progeny production neither accelerated nor delayed reproductive aging, indicating that reproductive aging is not controlled by use-dependent mechanisms. The implications of these findings for evolutionary theories of aging are discussed.
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Affiliation(s)
- Stacie E Hughes
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kimberley Evason
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Chengjie Xiong
- Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kerry Kornfeld
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * To whom correspondence should be addressed. E-mail:
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44
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Charmantier A, Perrins C, McCleery RH, Sheldon BC. Age-dependent genetic variance in a life-history trait in the mute swan. Proc Biol Sci 2006; 273:225-32. [PMID: 16555791 PMCID: PMC1560027 DOI: 10.1098/rspb.2005.3294] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 08/09/2005] [Indexed: 11/12/2022] Open
Abstract
Genetic variance in characters under natural selection in natural populations determines the way those populations respond to that selection. Whether populations show temporal and/or spatial constancy in patterns of genetic variance and covariance is regularly considered, as this will determine whether selection responses are constant over space and time. Much less often considered is whether characters show differing amounts of genetic variance over the life-history of individuals. Such age-specific variation, if present, has important potential consequences for the force of natural selection and for understanding the causes of variation in quantitative characters. Using data from a long-term study of the mute swan Cygnus olor, we report the partitioning of phenotypic variance in timing of breeding (subject to strong natural selection) into component parts over 12 different age classes. We show that the additive genetic variance and heritability of this trait are strongly age-dependent, with higher additive genetic variance present in young and, particularly, old birds, but little evidence of any genetic variance for birds of intermediate ages. These results demonstrate that age can have a very important influence on the components of variation of characters in natural populations, and consequently that separate age classes cannot be assumed to be equivalent, either with respect to their evolutionary potential or response.
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Affiliation(s)
- Anne Charmantier
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, UK.
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45
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Schmidt PS, Paaby AB, Heschel MS. GENETIC VARIANCE FOR DIAPAUSE EXPRESSION AND ASSOCIATED LIFE HISTORIES IN DROSOPHILA MELANOGASTER. Evolution 2005. [DOI: 10.1111/j.0014-3820.2005.tb00974.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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46
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Leips J, Gilligan P, Mackay TFC. Quantitative trait loci with age-specific effects on fecundity in Drosophila melanogaster. Genetics 2005; 172:1595-605. [PMID: 16272414 PMCID: PMC1456283 DOI: 10.1534/genetics.105.048520] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Life-history theory and evolutionary theories of aging assume the existence of alleles with age-specific effects on fitness. While various studies have documented age-related changes in the genetic contribution to variation in fitness components, we know very little about the underlying genetic architecture of such changes. We used a set of recombinant inbred lines to map and characterize the effects of quantitative trait loci (QTL) affecting fecundity of Drosophila melanogaster females at 1 and 4 weeks of age. We identified one QTL on the second chromosome and one or two QTL affecting fecundity on the third chromosome, but these QTL affected fecundity only at 1 week of age. There was more genetic variation for fecundity at 4 weeks of age than at 1 week of age and there was no genetic correlation between early and late-age fecundity. These results suggest that different loci contribute to the variation in fecundity as the organism ages. Our data provide support for the mutation accumulation theory of aging as applied to reproductive senescence. Comparing the results from this study with our previous work on life-span QTL, we also find evidence that antagonistic pleiotropy may contribute to the genetic basis of senescence in these lines as well.
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Affiliation(s)
- Jeff Leips
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21250, USA.
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47
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Carey JR, Liedo P, Müller HG, Wang JL, Senturk D, Harshman L. Biodemography of a long-lived tephritid: reproduction and longevity in a large cohort of female Mexican fruit flies, Anastrepha ludens. Exp Gerontol 2005; 40:793-800. [PMID: 16154309 PMCID: PMC2441917 DOI: 10.1016/j.exger.2005.07.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Revised: 06/24/2005] [Accepted: 07/19/2005] [Indexed: 11/19/2022]
Abstract
Age of sexual maturity, daily and lifetime reproductive rates, and life span were recorded in a laboratory cohort of Mexican fruit flies consisting of over 1100 females maintained individually. The results revealed that, relative to the medfly, the Mexfly is slower maturing (14 vs 17 days), more fecund (1400 vs 650-1100 eggs/female), and longer lived (50 vs 35 days). The results reinforced the generality of several earlier findings on the medfly including the deceleration of mortality at older ages and the weakness of the correlation between the rate of egg laying at early ages and both subsequent reproduction and remaining longevity. Discussion includes perspectives on the role of artificial selection in shaping the demographic traits of the mass-reared strain of Mexfly used in this study, as well as the overall significance of large scale biodemographic studies in understanding aging and longevity.
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Affiliation(s)
- James R Carey
- Department of Entomology, University of California, One Shields Avenue, Davis, CA 95616, USA.
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48
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Forbes SN, Valenzuela RK, Keim P, Service PM. Quantitative trait loci affecting life span in replicated populations of Drosophila melanogaster. I. Composite interval mapping. Genetics 2005; 168:301-11. [PMID: 15454544 PMCID: PMC1448087 DOI: 10.1534/genetics.103.023218] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Composite interval mapping was used to identify life-span QTL in F2 progeny of three crosses between different pairs of inbred lines. Each inbred line was derived from a different outbred population that had undergone long-term selection for either long or short life span. Microsatellite loci were used as genetic markers, and confidence intervals for QTL location were estimated by bootstrapping. A minimum of 10 QTL were detected, nine of which were located on the two major autosomes. Five QTL were present in at least two crosses and five were present in both sexes. Observation of the same QTL in more than one cross was consistent with the hypothesis that genetic variation for life span is maintained by balancing selection. For all QTL except one, allelic effects were in the direction predicted on the basis of outbred source population. Alleles that conferred longer life were always at least partially dominant.
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Affiliation(s)
- Scott N Forbes
- Department of Biological Sciences, Northern Arizona University, Flagstaff 86011, USA
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49
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Schmidt PS, Paaby AB, Heschel MS. GENETIC VARIANCE FOR DIAPAUSE EXPRESSION AND ASSOCIATED LIFE HISTORIES IN DROSOPHILA MELANOGASTER. Evolution 2005. [DOI: 10.1554/05-404.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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50
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Snoke MS, Promislow DEL. Quantitative genetic tests of recent senescence theory: age-specific mortality and male fertility in Drosophila melanogaster. Heredity (Edinb) 2003; 91:546-56. [PMID: 13130305 DOI: 10.1038/sj.hdy.6800353] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Quantitative genetic models of aging predict that additive genetic variance for fitness components should increase with age. However, recent studies have found that at very late ages, the genetic variance components decline. This decline may be due to an age-related drop in reproductive effort. If genetic variance in reproductive effort affects the genetic variance in mortality, the decline in reproductive effort at late ages should lead to a decrease in the genetic variance in mortality. To test this, we carried out a large-scale quantitative genetic analysis of age-specific mortality and fertility in virgin male Drosophila melanogaster. As in earlier studies, we found that the additive variance for age-specific mortality and fertility declined at late ages. Also, recent theoretical developments provide new predictions to distinguish between the mutation accumulation (MA) and antagonistic pleiotropy (AP) models of senescence. The deleterious effects of inbreeding are expected to increase with age under MA, but not under AP. This prediction was supported for both age-specific mortality and male fertility. Under AP, the ratio of dominance to additive variance is expected to decline with age. This predicition, too, was supported by the data analyzed here. Taken together, these analyses provide support for both the models playing a role in the aging process. We argue that the time has come to move beyond a simple comparison of these genetic models, and to think more deeply about the evolutionary causes and consequences of senescence.
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Affiliation(s)
- M S Snoke
- Department of Genetics, University of Georgia, Athens, GA 30602-7223, USA
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