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Sakai S. Maintenance of high inbreeding depression in selfing populations: Two-stage effect of early- and late-acting mutations. J Theor Biol 2020; 502:110307. [PMID: 32413353 DOI: 10.1016/j.jtbi.2020.110307] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/04/2020] [Accepted: 04/27/2020] [Indexed: 11/25/2022]
Abstract
High estimates of inbreeding depression have been obtained in many plant populations with high selfing rates. However, deleterious mutations might be purged from such populations as a result of selfing. I developed a simulation model assuming the presence of mutations at two sets of loci, namely, early- and late-acting loci, and the selective abortion of embryos coupled with ovule overproduction. In the model, early-acting loci are expressed during embryo initiation, and less vigorous embryos are aborted. Late-acting loci are expressed after selective abortion ends; the surviving embryos (seeds) compete, and some of them form the next generation. If mutations are allowed to occur in both early- and late-acting loci, both types increase in frequency in populations with high selfing rates. However, this phenomenon does not occur if mutations occur only in the early- or only in the late-acting loci. Consistent results are observed even if the total number of loci in which mutations are allowed to occur is the same for simulations with both early- and late-acting loci, only early-acting loci, or only late-acting loci, indicating that the presence of both types of loci is the causal factor. Thus, the two-stage effect, or occurrence of both early- and late-acting mutations, promotes the maintenance of these mutations in populations with high selfing rates.
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Affiliation(s)
- Satoki Sakai
- Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.
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2
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Stojanova B, Maurice S, Cheptou PO. Season-dependent effect of cleistogamy in Lamium amplexicaule: flower type origin versus inbreeding status. AMERICAN JOURNAL OF BOTANY 2020; 107:155-163. [PMID: 31889300 DOI: 10.1002/ajb2.1410] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Inbreeding depression is traditionally considered a major factor favoring outcrossing in hermaphrodites. Recent experiments have shown that environmental conditions can influence the magnitude of inbreeding depression, but their relevance in natural populations is unclear. To investigate this, we studied the cleistogamous species Lamium amplexicaule, an annual species with individuals experiencing either spring or autumn environmental conditions. In this species, the proportion of cleistogamous/chasmogamous flowers changes according to seasonal cues (e.g., temperature, photoperiod). Our hypothesis was that the plasticity of cleistogamy is an adaptation to seasonal fitness variation in different flower progenies. METHODS To test this hypothesis, we produced the three possible types of progenies through controlled crosses: (1) selfed progeny from cleistogamous flowers; (2) chasmogamous selfed progeny; and (3) chasmogamous outcrossed progeny. Progeny fitness was then measured in a common garden in the two reproduction seasons (autumn and spring). RESULTS The results showed that season had a major impact on fitness. The fitness of the different progeny types changed across seasons, indicating that the effect of cleistogamy on progeny performance is season-dependent, consistent with a previous study in a similar environment. Surprisingly, the flower from which the progeny issued (cleistogamous or chasmogamous) had more impact on fitness than the inbred status of the progeny (selfed versus outcrossed), suggesting a potential role of epigenetic processes. CONCLUSIONS The observed patterns of variation were not consistent either with adaptation to environment-dependent inbreeding depression or to variation in resource availability, but were possibly consistent with adaptation to seasonal pollinator activity.
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Affiliation(s)
- Bojana Stojanova
- Department of Biology and Ecology & Institute of Environmental Technologies, Faculty of Science, University of Ostrava, Chittussiho 10, 71000, Ostrava, Czech Republic
- ISEM, Université de Montpellier, CNRS, IRD, Montpellier, France
- CEFE, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valery, Montpellier, EPHE - 1919 route de Mende, 34293, Montpellier cedex 05, France
| | | | - Pierre-Olivier Cheptou
- CEFE, UMR 5175, CNRS, Université de Montpellier, Université Paul-Valery, Montpellier, EPHE - 1919 route de Mende, 34293, Montpellier cedex 05, France
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3
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Ismail SA, Kokko H. An analysis of mating biases in trees. Mol Ecol 2019; 29:184-198. [PMID: 31755136 PMCID: PMC7003921 DOI: 10.1111/mec.15312] [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: 10/04/2018] [Revised: 11/01/2019] [Accepted: 11/20/2019] [Indexed: 11/29/2022]
Abstract
Assortative mating is a deviation from random mating based on phenotypic similarity. As it is much better studied in animals than in plants, we investigate for trees whether kinship of realized mating pairs deviates from what is expected from the set of potential mates and use this information to infer mating biases that may result from kin recognition and/or assortative mating. Our analysis covers 20 species of trees for which microsatellite data is available for adult populations (potential mates) as well as seed arrays. We test whether mean relatedness of observed mating pairs deviates from null expectations that only take pollen dispersal distances into account (estimated from the same data set). This allows the identification of elevated as well as reduced kinship among realized mating pairs, indicative of positive and negative assortative mating, respectively. The test is also able to distinguish elevated biparental inbreeding that occurs solely as a result of related pairs growing closer to each other from further assortativeness. Assortative mating in trees appears potentially common but not ubiquitous: nine data sets show mating bias with elevated inbreeding, nine do not deviate significantly from the null expectation, and two show mating bias with reduced inbreeding. While our data sets lack direct information on phenology, our investigation of the phenological literature for each species identifies flowering phenology as a potential driver of positive assortative mating (leading to elevated inbreeding) in trees. Since active kin recognition provides an alternative hypothesis for these patterns, we encourage further investigations on the processes and traits that influence mating patterns in trees.
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Affiliation(s)
- Sascha A Ismail
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - Hanna Kokko
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
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4
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Servedio MR, Hermisson J. The evolution of partial reproductive isolation as an adaptive optimum. Evolution 2019; 74:4-14. [DOI: 10.1111/evo.13880] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 11/07/2019] [Indexed: 12/21/2022]
Affiliation(s)
- Maria R. Servedio
- Department of Biology University of North Carolina Chapel Hill North Carolina 27599
| | - Joachim Hermisson
- Mathematics and BioSciences Group, Faculty of Mathematics and Max F. Perutz Laboratories University of Vienna Vienna Austria
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5
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Huang Q, Burd M. The Effect of Pollen Limitation on the Evolution of Mating System and Seed Size in Hermaphroditic Plants. Am Nat 2019; 193:447-457. [DOI: 10.1086/701782] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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Ellison A, Rodríguez López CM, Moran P, Breen J, Swain M, Megias M, Hegarty M, Wilkinson M, Pawluk R, Consuegra S. Epigenetic regulation of sex ratios may explain natural variation in self-fertilization rates. Proc Biol Sci 2016; 282:rspb.2015.1900. [PMID: 26559950 DOI: 10.1098/rspb.2015.1900] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Self-fertilization (selfing) favours reproductive success when mate availability is low, but renders populations more vulnerable to environmental change by reducing genetic variability. A mixed-breeding strategy (alternating selfing and outcrossing) may allow species to balance these needs, but requires a system for regulating sexual identity. We explored the role of DNA methylation as a regulatory system for sex-ratio modulation in the mixed-mating fish Kryptolebias marmoratus. We found a significant interaction between sexual identity (male or hermaphrodite), temperature and methylation patterns when two selfing lines were exposed to different temperatures during development. We also identified several genes differentially methylated in males and hermaphrodites that represent candidates for the temperature-mediated sex regulation in K. marmoratus. We conclude that an epigenetic mechanism regulated by temperature modulates sexual identity in this selfing species, providing a potentially widespread mechanism by which environmental change may influence selfing rates. We also suggest that K. marmoratus, with naturally inbred populations, represents a good vertebrate model for epigenetic studies.
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Affiliation(s)
- Amy Ellison
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | | | - Paloma Moran
- Facultad de Biología, Universidad de Vigo, Vigo 36310, Spain
| | - James Breen
- School of Agriculture, Wine and Food, University of Adelaide, Adelaide 5005, Australia
| | - Martin Swain
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | - Manuel Megias
- Facultad de Biología, Universidad de Vigo, Vigo 36310, Spain
| | - Matthew Hegarty
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | - Mike Wilkinson
- School of Agriculture, Wine and Food, University of Adelaide, Adelaide 5005, Australia
| | - Rebecca Pawluk
- Department of Biosciences, College of Science, Swansea University, Swansea SA2 8PP, UK
| | - Sofia Consuegra
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK Department of Biosciences, College of Science, Swansea University, Swansea SA2 8PP, UK
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7
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Opedal ØH, Armbruster WS, Pélabon C. Inbreeding effects in a mixed-mating vine: effects of mating history, pollen competition and stress on the cost of inbreeding. AOB PLANTS 2015; 7:plv133. [PMID: 26578744 PMCID: PMC4683981 DOI: 10.1093/aobpla/plv133] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/07/2015] [Indexed: 06/01/2023]
Abstract
Inbreeding depression is assumed to be a central factor contributing to the stability of plant mating systems. Predicting the fitness consequence of inbreeding in natural populations is complicated, however, because it may be affected by the mating histories of populations generating variation in the amount of purging of deleterious alleles. Furthermore, the level of inbreeding depression may depend on environmental conditions and the intensity of pollen competition. In a greenhouse experiment comparing four populations of the neotropical vine Dalechampia scandens (Euphorbiaceae), we tested whether inbreeding depression for early-life fitness depended on the inferred mating history of each population, as indicated by genetically determined differences in herkogamy and autofertility rates. We also tested whether the intensity of pollen competition and the level of stress encountered by the seeds and seedlings affected the amount of inbreeding depression observed. Herkogamy was a good predictor of autofertility in each population. However, we found only limited evidence for inbreeding depression in any population, and inbreeding depression varied independently of the intensity of pollen competition and amount of stress encountered by the seeds and seedlings. Thus, the population's rate of autofertility did not predict the amount of inbreeding depression. Overall, we found no evidence supporting the expectations that more inbred populations experience less inbreeding depression, and that pollen competition reduces the cost of inbreeding. These results suggest that additional factors may be responsible for the maintenance of the mixed mating systems of D. scandens populations.
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Affiliation(s)
- Øystein H Opedal
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - W Scott Armbruster
- Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway School of Biological Sciences, University of Portsmouth, King Henry Building, King Henry I Street, Portsmouth PO1 2DY, UK Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA
| | - Christophe Pélabon
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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Lepers C, Dufay M, Billiard S. How does pollination mutualism affect the evolution of prior self-fertilization? A model. Evolution 2014; 68:3581-98. [PMID: 25314084 DOI: 10.1111/evo.12533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 09/28/2014] [Indexed: 11/27/2022]
Abstract
The mode of pollination is often neglected regarding the evolution of selfing. Yet the distribution of mating systems seems to depend on the mode of pollination, and pollinators are likely to interfere with selfing evolution, since they can cause strong selective pressures on floral traits. Most selfing species reduce their investment in reproduction, and display smaller flowers, with less nectar and scents (referred to as selfing syndrome). We model the evolution of prior selfing when it affects both the demography of plants and pollinators and the investment of plants in pollination. Including the selfing syndrome in the model allows to predict several outcomes: plants can evolve either toward complete outcrossing, complete selfing, or to a stable mixed-mating system, even when inbreeding depression is high. We predict that the evolution to high prior selfing could lead to evolutionary suicides, highlighting the importance of merging demography and evolution in models. The consequence of the selfing syndrome on plant-pollinator interactions could be a widespread mechanism driving the evolution of selfing in animal-pollinated taxa.
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Affiliation(s)
- Clotilde Lepers
- Laboratoire d'Evolution Ecologie et Paleontologie, UMR CNRS 8198 Bâtiment SN2, Université de Lille, F-59655, Villeneuve d'Ascq Cedex, France.
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9
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Devaux C, Lande R, Porcher E. Pollination ecology and inbreeding depression control individual flowering phenologies and mixed mating. Evolution 2014; 68:3051-65. [DOI: 10.1111/evo.12507] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 07/18/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Céline Devaux
- Institut des Sciences de l'Evolution de Montpellier; UMR 5554 34095 Montpellier France
| | - Russell Lande
- Division of Biology; Imperial College London; Silwood Park Campus; Ascot Berkshire SL5 7PY United Kingdom
| | - Emmanuelle Porcher
- Division of Biology; Imperial College London; Silwood Park Campus; Ascot Berkshire SL5 7PY United Kingdom
- Centre d'Ecologie et des Sciences de la Conservation; UMR MNHN-CNRS-UPMC 7204 75005 Paris France
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10
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Benesh DP, Weinreich F, Kalbe M, Milinski M. LIFETIME INBREEDING DEPRESSION, PURGING, AND MATING SYSTEM EVOLUTION IN A SIMULTANEOUS HERMAPHRODITE TAPEWORM. Evolution 2014; 68:1762-74. [DOI: 10.1111/evo.12388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 02/10/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel P. Benesh
- Department of Evolutionary Ecology; Max Planck Institute for Evolutionary Biology; August-Thienemann-Strasse 2 24306 Plön Germany
| | - Friederike Weinreich
- Department of Evolutionary Ecology; Max Planck Institute for Evolutionary Biology; August-Thienemann-Strasse 2 24306 Plön Germany
| | - Martin Kalbe
- Department of Evolutionary Ecology; Max Planck Institute for Evolutionary Biology; August-Thienemann-Strasse 2 24306 Plön Germany
| | - Manfred Milinski
- Department of Evolutionary Ecology; Max Planck Institute for Evolutionary Biology; August-Thienemann-Strasse 2 24306 Plön Germany
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11
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Hereford J. Inbreeding depression does not increase in foreign environments: a field experimental study. AOB PLANTS 2014; 6:plu009. [PMID: 24790130 PMCID: PMC4038437 DOI: 10.1093/aobpla/plu009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 02/07/2014] [Indexed: 06/02/2023]
Abstract
Early successional species often disperse to novel environments, and if they are selfing, this dispersal will frequently be carried out by inbred individuals. If inbred immigrants are less likely to successfully establish populations than outbred immigrants, dispersal will be less effective and mating system evolution will favour outcrossing. I performed a reciprocal transplant of inbred and outbred plants grown in native and foreign planting sites to test the hypothesis that inbred immigrants had lower fitness. Inbreeding within populations was estimated with allozyme loci to confirm that the populations were inbred. While inbred and outbred plants had significantly lower fitness in foreign habitats, inbreeding depression was of similar magnitude at native sites and foreign habitats. There was no significant difference between inbred and outbred plants at foreign sites of the native habitat. Populations appear to be highly selfing, yet there is an advantage to outcrossing in both the native environment and foreign environments. The implications of this advantage with respect to mating system evolution may depend on whether novel environments are occupied or unoccupied.
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Affiliation(s)
- Joe Hereford
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
- Present address: Department of Evolution and Ecology, University of California, Davis, Davis, CA 95616, USA
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12
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Jorgensen R, Arathi HS. Floral longevity and autonomous selfing are altered by pollination and water availability in Collinsia heterophylla. ANNALS OF BOTANY 2013; 112:821-8. [PMID: 23884393 PMCID: PMC3747799 DOI: 10.1093/aob/mct146] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/07/2013] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS A plant investing in reproduction partitions resources between flowering and seed production. Under resource limitation, altered allocations may result in floral trait variations, leading to compromised fecundity. Floral longevity and timing of selfing are often the traits most likely to be affected. The duration of corolla retention determines whether fecundity results from outcrossing or by delayed selfing-mediated reproductive assurance. In this study, the role of pollination schedules and soil water availability on floral longevity and seed production is tested in Collinsia heterophylla (Plantaginaceae). METHODS Using three different watering regimes and pollination schedules, effects on floral longevity and seed production were studied in this protandrous, flowering annual. KEY RESULTS The results reveal that soil water status and pollination together influence floral longevity with low soil water and hand-pollinations early in the floral lifespan reducing longevity. However, early pollinations under excess water did not extend longevity, implying that resource surplus does not lengthen the outcrossing period. The results also indicate that pollen receipt, a reliable cue for fecundity, accelerates flower drop. Early corolla abscission under drought stress could potentially exacerbate sexual conflict in this protandrous, hermaphroditic species by ensuring self-pollen paternity and enabling male control of floral longevity. While pollination schedules did not affect fecundity, water stress reduced per-capita seed numbers. Unmanipulated flowers underwent delayed autonomous selfing, producing very few seeds, suggesting that inbreeding depression may limit benefits of selfing. CONCLUSIONS In plants where herkogamy and dichogamy facilitate outcrossing, floral longevity determines reproductive success and mating system. Reduction in longevity under drought suggests a strong environmental effect that could potentially alter the preferred breeding mode in this mixed-mated species. Extrapolating the findings to unpredictable global drought cycles, it is suggested that in addition to reducing yield, water stress may influence the evolutionary trajectory of plant mating system.
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13
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Mathias A, Chesson P. Coexistence and evolutionary dynamics mediated by seasonal environmental variation in annual plant communities. Theor Popul Biol 2012; 84:56-71. [PMID: 23287702 DOI: 10.1016/j.tpb.2012.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2011] [Revised: 11/22/2012] [Accepted: 11/28/2012] [Indexed: 11/28/2022]
Abstract
It is well established theoretically that competing species may coexist by having different responses to variation over time in the physical environment. Whereas previous theory has focused mostly on year-to-year environmental variation, we investigate how within-year variation can be the basis of species coexistence. We ask also the important but often neglected question of whether the species differences that allow coexistence are compatible with evolutionary processes. We seek the simplest circumstances that permit coexistence based on within-year environmental variation, and then evaluate the robustness of coexistence in the face of evolutionary forces. Our focus is on coexistence of annual plant species living in arid regions. We first consider environmental variation of a very simple structure where a single pulse of rain occurs, and different species have different patterns of growth activity following the rain pulse. We show that coexistence of two species is possible based on the storage effect coexistence mechanism in this simplest of varying environments. We find an exact expression for the magnitude of the storage effect that allows the functioning of the coexistence mechanism to be analyzed. However, in these simplest of circumstances, coexistence in our models is not evolutionarily stable. Increasing the complexity of the environment to two rain pulses leads to evolutionarily stable species coexistence, and a route to diversity via evolutionary branching. This demonstration of the compatibility of a coexistence mechanism with evolutionary processes is an important step in assessing the likely importance of a mechanism in nature.
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Affiliation(s)
- Andrea Mathias
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.
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14
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Cheptou PO, Donohue K. Epigenetics as a new avenue for the role of inbreeding depression in evolutionary ecology. Heredity (Edinb) 2012; 110:205-6. [PMID: 23047201 DOI: 10.1038/hdy.2012.66] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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Lobo J, Solís S, Fuchs EJ, Quesada M. Individual and Temporal Variation in Outcrossing Rates and Pollen Flow Patterns inCeiba pentandra(Malvaceae: Bombacoidea). Biotropica 2012. [DOI: 10.1111/btp.12001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Jorge Lobo
- Escuela de Biología; Universidad de Costa Rica; 2060; San José; Costa Rica
| | - Silvia Solís
- Centro de Investigaciones en Ecosistemas; Universidad Nacional Autónoma de México; Apartado Postal 27-3 (Xangari); 58089; Morelia; Michoacan; Mexico
| | - Eric J. Fuchs
- Escuela de Biología; Universidad de Costa Rica; 2060; San José; Costa Rica
| | - Mauricio Quesada
- Centro de Investigaciones en Ecosistemas; Universidad Nacional Autónoma de México; Apartado Postal 27-3 (Xangari); 58089; Morelia; Michoacan; Mexico
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16
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Variability of individual genetic load: consequences for the detection of inbreeding depression. Genetica 2012; 140:39-51. [PMID: 22638826 DOI: 10.1007/s10709-012-9656-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 05/02/2012] [Indexed: 10/28/2022]
Abstract
Inbreeding depression is a key factor affecting the persistence of natural populations, particularly when they are fragmented. In species with mixed mating systems, inbreeding depression can be estimated at the population level by regressing the average progeny fitness by the selfing rate of their mothers. We applied this method using simulated populations to investigate how population genetic parameters can affect the detection power of inbreeding depression. We simulated individual selfing rates and genetic loads from which we computed fitness values. The regression method yielded high statistical power, inbreeding depression being detected as significant (5 % level) in 92 % of the simulations. High individual variation in selfing rate and high mean genetic load led to better detection of inbreeding depression while high among-individual variation in genetic load made it more difficult to detect inbreeding depression. For a constant sampling effort, increasing the number of progenies while decreasing the number of individuals per progeny enhanced the detection power of inbreeding depression. We discuss the implication of among-mother variability of genetic load and selfing rate on inbreeding depression studies.
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Winn AA, Elle E, Kalisz S, Cheptou PO, Eckert CG, Goodwillie C, Johnston MO, Moeller DA, Ree RH, Sargent RD, Vallejo-Marín M. Analysis of inbreeding depression in mixed-mating plants provides evidence for selective interference and stable mixed mating. Evolution 2011; 65:3339-59. [PMID: 22133210 DOI: 10.1111/j.1558-5646.2011.01462.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of selfing, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r > 0.8), mixed-mating (0.2 ≤ r ≥ 0.8), and highly outcrossing (r < 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (δ= 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them.
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Affiliation(s)
- Alice A Winn
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA.
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Coutellec MA, Caquet T. Heterosis and inbreeding depression in bottlenecked populations: a test in the hermaphroditic freshwater snail Lymnaea stagnalis. J Evol Biol 2011; 24:2248-57. [PMID: 21767319 DOI: 10.1111/j.1420-9101.2011.02355.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Small population size is expected to induce heterosis, due to the random fixation and accumulation of mildly deleterious mutations, whereas within-population inbreeding depression should decrease due to increased homozygosity. Population bottlenecks, although less effective, may have similar consequences. We tested this hypothesis in the self-fertile freshwater snail Lymnaea stagnalis, by subjecting experimental populations to a single bottleneck of varied magnitude. Although patterns were not strong, heterosis was significant in the most severely bottlenecked populations, under stressful conditions. This was mainly due to hatching rate, suggesting that early acting and highly deleterious alleles were involved. Although L. stagnalis is a preferential outcrosser, inbreeding depression was very low and showed no clear relationship with bottleneck size. In the less reduced populations, inbreeding depression for hatching success increased under high inbreeding. This may be consistent with the occurence of synergistic epistasis between fitness loci, which may contribute to favour outcrossing in L. stagnalis.
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Affiliation(s)
- M-A Coutellec
- INRA, UMR 0985 ESE, Agrocampus-Ouest, Equipe Ecotoxicologie et Qualité des Milieux Aquatiques, Rennes Cedex, France.
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Affiliation(s)
- Jeremiah W. Busch
- School of Biological Sciences, Washington State University, Pullman, Washington 99164
- E‐mail:
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Escobar JS, Auld JR, Correa AC, Alonso JM, Bony YK, Coutellec M, Koene JM, Pointier J, Jarne P, David P. PATTERNS OF MATING‐SYSTEM EVOLUTION IN HERMAPHRODITIC ANIMALS: CORRELATIONS AMONG SELFING RATE, INBREEDING DEPRESSION, AND THE TIMING OF REPRODUCTION. Evolution 2011; 65:1233-53. [DOI: 10.1111/j.1558-5646.2011.01218.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Juan S. Escobar
- Centre d’Ecologie Fonctionnelle et Evolutive UMR 5175, 1919 Route de Mende, Campus CNRS, 34293 Montpellier Cedex 5, France
- E‐mail:
| | - Josh R. Auld
- University of Pittsburgh, Department of Biological Sciences, 101 Clapp Hall, 4249 Fifth Avenue, Pittsburgh, Pennsylvania 15260
| | - Ana C. Correa
- Institut de Recherche pour le Développement, GEMI UMR 2724 CNRS‐IRD, 911 Avenue Agropolis, 34394 Montpellier, France
- Programa de Estudio y Control de Enfermedades Tropicales, Universidad de Antioquia, Calle 62 N° 52–59, Sede de Investigación Universitaria, Medellin, Colombia
| | - Juan M. Alonso
- USR 3278 CNRS‐EPHE CRIOBE, Université de Perpignan, 68860 Perpignan cedex, France
| | - Yves K. Bony
- USR 3278 CNRS‐EPHE CRIOBE, Université de Perpignan, 68860 Perpignan cedex, France
- Department of Biological Sciences, Laboratoire d’Environnement et de Biologie Aquatique (LEBA), URES de Daloa (University of Abobo‐Adjamé), 28 BP 465, Abidjan 28, Ivory Coast
| | - Marie‐Agnès Coutellec
- Institut National de Recherche Agronomique, UMR0985 Ecologie et Santé des Ecosystèmes, 65 rue de Saint‐Brieuc, CS 84215, F‐35042 Rennes Cedex, France
| | - Joris M. Koene
- Animal Ecology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
| | - Jean‐Pierre Pointier
- USR 3278 CNRS‐EPHE CRIOBE, Université de Perpignan, 68860 Perpignan cedex, France
| | - Philippe Jarne
- Centre d’Ecologie Fonctionnelle et Evolutive UMR 5175, 1919 Route de Mende, Campus CNRS, 34293 Montpellier Cedex 5, France
| | - Patrice David
- Centre d’Ecologie Fonctionnelle et Evolutive UMR 5175, 1919 Route de Mende, Campus CNRS, 34293 Montpellier Cedex 5, France
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21
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Costa E Silva J, Hardner C, Tilyard P, Potts BM. The effects of age and environment on the expression of inbreeding depression in Eucalyptus globulus. Heredity (Edinb) 2011; 107:50-60. [PMID: 21224873 DOI: 10.1038/hdy.2010.154] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Inbreeding adversely affects fitness traits in many plant and animal species, and the magnitude, stability and genetic basis of inbreeding depression (ID) will have short- and long-term evolutionary consequences. The effects of four degrees of inbreeding (selfing, f=50%; full- and half-sib matings, f=25 and 12.5%; and unrelated outcrosses, f=0%) on survival and growth of an island population of Eucalyptus globulus were studied at two sites for over 14 years. For selfs, ID in survival increased over time, reaching a maximum of 49% by age 14 years. However, their inbreeding depression for stem diameter remained relatively stable with age, and ranged from 28 to 36% across years and sites. ID for survival was markedly greater on the more productive site, possibly due to greater and earlier onset of inter-tree competition, but was similar on both sites for the diameter of survivors. The deleterious trait response to increasing inbreeding coefficients was linear for survival and diameter. Non-significant quadratic effects suggested that epistasis did not contribute considerably to the observed ID at the population level. Among- and within-family coefficients of variation for diameter increased with inbreeding degree, and the variance among the outcrossed families was significant only on the more productive site. The performance of self-families for diameter was highly stable between sites. This suggests that, for species with mixed mating systems, environmentally stable inbreeding effects in open-pollinated progenies may tend to mask the additive genotype-by-environment interaction for fitness traits and the adaptive response to the environment.
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Affiliation(s)
- J Costa E Silva
- Centro de Estudos Florestais, Departamento de Ambiente, Território e Recursos Naturais, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Portugal
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22
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Cheptou PO, Donohue K. Environment-dependent inbreeding depression: its ecological and evolutionary significance. THE NEW PHYTOLOGIST 2011; 189:395-407. [PMID: 21091479 DOI: 10.1111/j.1469-8137.2010.03541.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Inbreeding depression is a major evolutionary and ecological force that influences population dynamics and the evolution of inbreeding-avoidance traits such as mating systems and dispersal. There is now compelling evidence that inbreeding depression is environment-dependent. Here, we discuss ecological and evolutionary consequences of environment-dependent inbreeding depression. The environmental dependence of inbreeding depression may be caused by environment-dependent phenotypic expression, environment-dependent dominance, and environment-dependent natural selection. The existence of environment-dependent inbreeding depression challenges classical models of inbreeding as caused by unconditionally deleterious alleles, and suggests that balancing selection may shape inbreeding depression in natural populations; loci associated with inbreeding depression in some environments may even contribute to adaptation to others. Environment-dependent inbreeding depression also has important, often neglected, ecological and evolutionary consequences: it can influence the demography of marginal or colonizing populations and alter adaptive optima of mating systems, dispersal, and their associated traits. Incorporating the environmental dependence of inbreeding depression into theoretical models and empirical studies is necessary for understanding the genetic and ecological basis of inbreeding depression and its consequences in natural populations.
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Affiliation(s)
- Pierre-Olivier Cheptou
- UMR 5175 CEFE - Centre d'Ecologie Fonctionnelle et Evolutive (CNRS), 1919 Route de Mende, F-34293 Montpellier, Cedex 05, France.
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23
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Sasaki A, Dieckmann U. Oligomorphic dynamics for analyzing the quantitative genetics of adaptive speciation. J Math Biol 2010; 63:601-35. [DOI: 10.1007/s00285-010-0380-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 10/08/2010] [Indexed: 10/18/2022]
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24
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Massol F, Cheptou PO. Evolutionary syndromes linking dispersal and mating system: the effect of autocorrelation in pollination conditions. Evolution 2010; 65:591-8. [PMID: 21271998 DOI: 10.1111/j.1558-5646.2010.01134.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Self-fertilization is classically thought to be associated with propagule dispersal because self-fertilization is a boon to colonizers entering environments devoid of pollinators or potential mates. Yet, it has been theoretically shown that random fluctuations in pollination conditions select for the opposite association of traits. In nature, however, various ecological factors may deviate from random variations, and thus create temporal correlation in pollination conditions. Here, we develop a model to assess the effects of pollination condition autocorrelation on the joint evolution of dispersal and self-fertilization. Basically, two syndromes are found: dispersing outcrossers and nondispersing (partial) selfers. Importantly, (1) selfers are never associated with dispersal, whereas complete outcrossers are, and (2) the disperser/outcrosser syndrome is favored (resp. disfavored) by negative (resp. positive) autocorrelation in pollination conditions. Our results suggest that observed dispersal/mating system syndromes may depend heavily on the regime of pollination condition fluctuations. We also point out potential negative evolutionary effects of anthropic management of the environment on outcrossing species.
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Affiliation(s)
- François Massol
- CEMAGREF - UR HYAX, 3275, route de Cézanne - Le Tholonet, CS 40061, 13182 Aix-en-Provence cedex 5, France.
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25
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Escobar JS, Facon B, Jarne P, Goudet J, David P. CORRELATED EVOLUTION OF MATING STRATEGY AND INBREEDING DEPRESSION WITHIN AND AMONG POPULATIONS OF THE HERMAPHRODITIC SNAILPHYSA ACUTA. Evolution 2009; 63:2790-804. [DOI: 10.1111/j.1558-5646.2009.00760.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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26
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Epinat G, Lenormand T. THE EVOLUTION OF ASSORTATIVE MATING AND SELFING WITH IN- AND OUTBREEDING DEPRESSION. Evolution 2009; 63:2047-60. [DOI: 10.1111/j.1558-5646.2009.00700.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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27
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Gottlieb D, Holzman JP, Lubin Y, Bouskila A, Kelley ST, Harari AR. Mate availability contributes to maintain the mixed-mating system in a scolytid beetle. J Evol Biol 2009; 22:1526-34. [PMID: 19496926 DOI: 10.1111/j.1420-9101.2009.01763.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daphna Gottlieb
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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28
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Ronce O, Shaw FH, Rousset F, Shaw RG. IS INBREEDING DEPRESSION LOWER IN MALADAPTED POPULATIONS? A QUANTITATIVE GENETICS MODEL. Evolution 2009; 63:1807-19. [DOI: 10.1111/j.1558-5646.2009.00678.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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29
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PORCHER E, KELLY JK, CHEPTOU PO, ECKERT CG, JOHNSTON MO, KALISZ S. The genetic consequences of fluctuating inbreeding depression and the evolution of plant selfing rates. J Evol Biol 2009; 22:708-17. [DOI: 10.1111/j.1420-9101.2009.01705.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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30
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Steets JA, Wolf DE, Auld JR, Ashman TL. The role of natural enemies in the expression and evolution of mixed mating in hermaphroditic plants and animals. Evolution 2007; 61:2043-55. [PMID: 17767581 DOI: 10.1111/j.1558-5646.2007.00184.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although a large portion of plant and animal species exhibit intermediate levels of outcrossing, the factors that maintain this wealth of variation are not well understood. Natural enemies are one relatively understudied ecological factor that may influence the evolutionary stability of mixed mating. In this paper, we aim for a conceptual unification of the role of enemies in mating system expression and evolution in both hermaphroditic animals and plants. We review current theory and detail the potential effects of enemies on fundamental mating system parameters. In doing so, we identify situations in which consideration of enemies alters expectations about the stability of mixed mating. Generally, we find that inclusion of the enemy dimension may broaden conditions in which mixed mating systems are evolutionarily stable. Finally, we highlight avenues ripe for future theoretical and empirical work that will advance our understanding of enemies in the expression and evolution of mixed mating in their hosts/victims, including examination of feedback cycles between victims and enemies and quantification of mating system-related parameters in victim populations in the presence and absence of enemies.
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Affiliation(s)
- Janette A Steets
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA.
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31
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Sebastián Escobar J, Epinat G, Sarda V, David P. NO CORRELATION BETWEEN INBREEDING DEPRESSION AND DELAYED SELFING IN THE FRESHWATER SNAIL PHYSA ACUTA. Evolution 2007; 61:2655-70. [PMID: 17894808 DOI: 10.1111/j.1558-5646.2007.00223.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Inbreeding depression, one of the main factors driving mating system evolution, can itself evolve as a function of the mating system (the genetic purging hypothesis). Classical models of coevolution between mating system and inbreeding depression predict negative associations between inbreeding depression and selfing rate, but more recent approaches suggest that negative correlations should usually be too weak or transient to be detected within populations. Empirical results remain unclear and restricted to plants. Here, we evaluate, for the first time, the within-population genetic correlation between inbreeding depression and a trait that controls the amount of self-fertilization (the waiting time) in a self-fertile hermaphroditic animal, the freshwater snail Physa acuta. Using a large quantitative-genetic design (36 grand-families and 348 families), we observe abundant within-population family-level genetic variation for both inbreeding depression (estimated for survival, fecundity, and size) and the degree of behavioral selfing avoidance. However, we detected no correlation between waiting time and inbreeding depression across families. In agreement with recent models, this result shows that mutational variance rather than differential purging accounts for most of the genetic variance in inbreeding depression within a population.
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Affiliation(s)
- Juan Sebastián Escobar
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175 CNRS, 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
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32
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Koslow JM, Clay K. THE MIXED MATING SYSTEM OF IMPATIENS CAPENSIS AND INFECTION BY A FOLIAR RUST PATHOGEN: PATTERNS OF RESISTANCE AND FITNESS CONSEQUENCES. Evolution 2007; 61:2643-54. [PMID: 17894807 DOI: 10.1111/j.1558-5646.2007.00224.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Outcrossing by hosts may offer protection from natural enemies adapted to parental genotypes by creating diverse progeny that differ from their parents through genetic recombination. However, past experimental work addressing the relationship between mating system and disease in offspring has given conflicting results, suggesting that outcrossing might also cause the dissolution of resistant genotypes. To determine if selfed progeny are more susceptible to disease caused by the heteroecious rust, Puccinia recondita, or if selfing preserves existing resistant genotypes, we used a factorial design to compare levels of infection of selfed and outcrossed progeny of Impatiens capensis, a woodland annual with a mixed mating system. We compared the level of host infection when exposed to three pathogen sources in the field: the sympatric rust population, and two allopatric rust populations. Outcrossed progeny exposed to sympatric rust had higher infection scores than selfed progeny exposed to the same rust, suggesting that outcrossing breaks up resistant genotypes. In addition, there was a trend for the rust to be more infective on sympatric rather than allopatric hosts. We also examined whether rust infection differentially alters the fitness of selfed and outcrossed progeny. Outcrossed plants that escaped infection had higher fitness, as measured by fruit production, than selfed plants, but there was no difference in fitness between infected selfed and infected outcrossed plants. Thus, outcrossing was advantageous in the absence of disease, but there was no fitness difference between selfed and outcrossed progeny in the presence of disease. In sum, our results indicate that interactions with pathogens can eliminate or reverse the advantage of outcrossing.
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Affiliation(s)
- Jennifer M Koslow
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA.
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33
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Ito HC, Dieckmann U. A new mechanism for recurrent adaptive radiations. Am Nat 2007; 170:E96-111. [PMID: 17891728 DOI: 10.1086/521229] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2006] [Accepted: 05/17/2007] [Indexed: 11/03/2022]
Abstract
Models of adaptive radiation through intraspecific competition have attracted mounting attention. Here we show how extending such models in a simple manner, by including a quantitative trait under weak directional selection, naturally leads to rich macroevolutionary patterns involving recurrent adaptive radiations and extinctions. Extensive tests demonstrate the robustness of this finding to a wide range of variations in model assumptions. In particular, recurrent adaptive radiations and extinctions readily unfold both for asexual and for sexual populations. Since the mechanisms driving the investigated processes of endogenous diversification result from generic geometric features of the underlying fitness landscapes--frequency-dependent disruptive selection in one trait and weak directional selection in another--the reported phenomena can be expected to occur in a wide variety of eco-evolutionary settings.
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Affiliation(s)
- Hiroshi C Ito
- Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
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34
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Steets JA, Knight TM, Ashman TL. The interactive effects of herbivory and mixed mating for the population dynamics of Impatiens capensis. Am Nat 2007; 170:113-27. [PMID: 17853996 DOI: 10.1086/518178] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 02/01/2007] [Indexed: 11/03/2022]
Abstract
In this study, we examine the demographic consequences of mixed mating and explore the interactive effects of vegetative herbivory and mating system for population dynamics of Impatiens capensis, a species with an obligate mixed mating system (i.e., individuals produce both obligately selfing cleistogamous and facultatively outcrossing chasmogamous flowers). In two natural populations, we followed seeds derived from cleistogamous and chasmogamous flowers subject to different herbivory levels throughout their life cycle. Using a mating system-explicit projection matrix model, we found that mating system types differed in important vital rates. Cleistogamous individuals had higher rates of germination than did chasmogamous individuals, whereas chasmogamous individuals expressed a fecundity advantage over cleistogamous individuals. In addition, population growth was most sensitive to changes in vital rates of cleistogamous individuals, indicating the demographic importance of selfing for these populations. Herbivory also had demographic consequences; a 33%-49% reduction in herbivory caused the population growth rates to increase by 104%-132%, primarily because of effects on vital rates of selfed individuals. Our results not only uncover a novel consequence of mating system expression, that is, mating system influences population dynamics, but also shed light on the role of herbivores in maintaining mixed mating.
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Affiliation(s)
- Janette A Steets
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
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35
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Affiliation(s)
- Hanna Kokko
- Laboratory of Ecological and Evolutionary Dynamics, Department of Biological and Environmental Science, University of Helsinki, FIN‐00014 Helsinki, Finland E‐mail:
| | - Indrek Ots
- Institute of Zoology and Hydrobiology, Tartu University, Estonia E‐mail:
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36
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Lankinen A, Armbruster WS. Pollen competition reduces inbreeding depression in Collinsia heterophylla (Plantaginaceae). J Evol Biol 2007; 20:737-49. [PMID: 17305839 DOI: 10.1111/j.1420-9101.2006.01233.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We tested two predictions of the hypothesis that competition between self-pollen may mitigate negative genetic effects of inbreeding in plants: (1) intense competition among self-pollen increases offspring fitness; and (2) pollen competition reduces the measured strength of inbreeding depression. We used Collinsia heterophylla (Plantaginaceae), an annual with a mixed mating system, to perform controlled crosses in which we varied both the size of the pollen load and the source of pollen (self vs. outcross). Fitness of selfed offspring was higher in the high pollen-load treatment. Our second prediction was also upheld: inbreeding depression was, on average, lower when large pollen loads were applied (11%) relative to the low pollen-load treatment (28%). The reduction was significant for two fitness components relatively late in the life-cycle: number of surviving seedlings and pollen-tube growth rate in vitro. These findings suggest that intermittent inbreeding, which leads to self-fertilization in plants with genetic loads, may select for traits that enhance pollen competition.
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Affiliation(s)
- A Lankinen
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway.
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37
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Galloway LF, Etterson JR. Inbreeding depression in an autotetraploid herb: a three cohort field study. THE NEW PHYTOLOGIST 2007; 173:383-92. [PMID: 17204084 DOI: 10.1111/j.1469-8137.2006.01909.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Autotetraploids are predicted to have reduced inbreeding depression relative to diploids. However, recent theory and information on genomic changes following autopolyploidy suggest that inbreeding depression may be closer to diploids. In three consecutive years, self and outcross pollinations were conducted on autotetraploid Campanulastrum americanum, seeds were planted into native sites, and biennial offspring were followed through seed production. Inbred individuals had lower germination rates, reduced survival, were smaller, and flowered later, producing fewer fruits with fewer seeds. Inbred offspring had 6% of the cumulative fitness of outcross offspring. Although performance varied substantially among cohorts, inbreeding depression for cumulative fitness was relatively constant, with delta ranging only from 0.92 to 0.95. C. americanum, like many outcrossing species, expressed very high amounts of inbreeding depression. This supports the hypothesis that inbreeding depression of some autotetraploids may be similar to that of diploids. Furthermore, few studies have measured temporal variation in inbreeding depression. Constant inbreeding depression given a sixfold range in cohort performance suggests that inbreeding depression may be relatively robust to environmental variation experienced by natural populations.
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Affiliation(s)
- Laura F Galloway
- Department of Biology, University of Virginia, Charlottesville, VA 22904-4328, USA.
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38
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Abstract
Breeding systems are important, and often neglected, aspects of the natural biology of organisms, affecting homozygosity and thus many aspects of their biology, including levels and patterns of genetic diversity and genome evolution. Among the different plant mating systems, it is useful to distinguish two types of systems: 'sex systems', hermaphroditic versus male/female and other situations; and the 'mating systems' of hermaphroditic populations, inbreeding, outcrossing or intermediate. Evolutionary changes in breeding systems occur between closely related species, and some changes occur more often than others. Understanding why such changes occur requires combined genetical and ecological approaches. I review the ideas of some of the most important theoretical models, showing how these are based on individual selection using genetic principles to ask whether alleles affecting plants' outcrossing rates or sex morphs will spread in populations. After discussing how the conclusions are affected by some of the many relevant ecological factors, I relate these theoretical ideas to empirical data from some of the many recent breeding system studies in plant populations.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab. King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
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39
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Jokela J, Wiehn J, Kopp K. Among- and within-population variation in outcrossing rate of a mixed-mating freshwater snail. Heredity (Edinb) 2006; 97:275-82. [PMID: 16721388 DOI: 10.1038/sj.hdy.6800851] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mixed-mating animals self-fertilize a proportion of their offspring. Outcrossing rate may covary with the ecological and historical factors affecting the population. Theory predicts that outcrossing is favored when inbreeding depression is high and when individual heterozygosity is important. Self-fertilization is predicted to be favored when costs of male function, or mate finding are high, for example, when empty patches are colonized by few individuals. In this study, we assessed primary (after hatching) and secondary (after juvenile mortality) outcrossing rates of two mixed-mating snail populations. Our purpose was to assess the variation in mating-system parameters and estimate significance of inbreeding depression for secondary outcrossing rate (the realized outcrossing rate of parents that produce the next generation). Secondary outcrossing rate was higher than the primary outcrossing rate in one of the two populations, suggesting considerable inbreeding depression. In the other study population, secondary outcrossing rates were found to increase when initially low, or decrease when initially high, depending on the family. Moderate outcrossing rates were found to be more stable. Parental inbreeding coefficients were close to zero in both populations. Outcrossing rate was much more variable among families in the population with the lower average outcrossing rate, suggesting that individuals differed considerably in their mating system. Our results add to recent studies suggesting that populations of mixed-mating animals may differ in their mating system parameters and expression of inbreeding depression.
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Affiliation(s)
- J Jokela
- Department of Environmental Sciences, ETH-Zürich, Institute of Integrative Biology (IBZ), Zürich, Switzerland.
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40
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Coutellec MA, Lagadic L. Effects of self-fertilization, environmental stress and exposure to xenobiotics on fitness-related traits of the freshwater snail Lymnaea stagnalis. ECOTOXICOLOGY (LONDON, ENGLAND) 2006; 15:199-213. [PMID: 16425104 DOI: 10.1007/s10646-005-0049-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 09/30/2005] [Indexed: 05/06/2023]
Abstract
Genetic and ecological factors may interact in their effects on fitness. Such interactions are thus to be expected between inbreeding and exposure of a population to a toxicant. The magnitude of inbreeding depression is thought to increase in stressful environments. To test this hypothesis, we investigated the combined effects of environmental conditions and inbreeding on fitness in the self-fertile snail Lymnaea stagnalis, using a stress gradient (0-2) applied to a 100 isolated and paired lineages: laboratory control (0), outdoor microcosm control (1) and pesticide exposure under outdoor microcosm conditions (2). Outdoor stress conditions were maintained for 28 days prior to measurements of fitness traits (fecundity, hatching success, and size at hatching) under laboratory conditions, so that delayed environmental effects could be estimated. Under laboratory control conditions, we found significant initial family level heterogeneity for most measured traits, including physiological performances as assessed through energetic biomarkers. Whatever the environmental conditions, inbreeding depression was very low for progeny performances. Negative values of self-fertilization depression (SFD) were obtained. Unexpectedly, SFD showed a negative relationship with the assumed stress intensity, reflecting a higher sensitivity under pairing than under selfing, mostly due to parental fecundity. This suggests that stressful conditions may favour selfing. Stress intensity increased the distribution limits of both depression indices, suggesting that changes in fitness are less predictable in a population under stress. Implications of such findings for environmental risk assessment of pesticides are discussed.
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Affiliation(s)
- Marie-Agnès Coutellec
- UMR 985 INRA-Agrocampus Ecobiologie et Qualité des Hydrosystèmes Continentaux, Equipe Ecotoxicologie et Qualité des Milieux aquatiques, 65 rue de St-Brieuc, F-35042, Rennes cedex, France.
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41
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Ishida K. Maintenance of Inbreeding Depression in a Highly Self-Fertilizing Tree, Magnolia obovata Thunb. Evol Ecol 2006. [DOI: 10.1007/s10682-005-5748-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Goodwillie C, Kalisz S, Eckert CG. The Evolutionary Enigma of Mixed Mating Systems in Plants: Occurrence, Theoretical Explanations, and Empirical Evidence. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2005. [DOI: 10.1146/annurev.ecolsys.36.091704.175539] [Citation(s) in RCA: 773] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Carol Goodwillie
- 1Department of Biology, East Carolina University, Greenville, North Carolina 27858;
| | - Susan Kalisz
- 2Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260;
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Zhang Y, Yang J, Rao GY. Genetic diversity of an amphicarpic species, Amphicarpaea edgeworthii Benth. (Leguminosae) based on RAPD markers. BIOCHEM SYST ECOL 2005. [DOI: 10.1016/j.bse.2005.07.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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45
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Joron M, Iwasa Y. The evolution of a Müllerian mimic in a spatially distributed community. J Theor Biol 2005; 237:87-103. [PMID: 15975598 DOI: 10.1016/j.jtbi.2005.04.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 03/31/2005] [Accepted: 04/01/2005] [Indexed: 11/23/2022]
Abstract
Strong positive density-dependence should lead to a loss of diversity, but warning-colour and Müllerian mimicry systems show extraordinary levels of diversity. Here, we propose an analytical model to explore the dynamics of two forms of a Müllerian mimic in a heterogeneous environment with two alternative model species. Two connected populations of a dimorphic, chemically defended mimic are allowed to evolve and disperse. The proportions of the respective model species vary spatially. We use a nonlinear approximation of Müller's number-dependent equations to model a situation where the mortality for either form of the mimic decreases hyberbolically when its local density increases. A first non-spatial analysis confirms that the positive density-dependence makes coexistence of mimetic forms unstable in a single isolated patch, but shows that mimicry of the rarer model can be stable once established. The two-patch analysis shows that when models have different abundance in different places, local mimetic diversity in the mimic is maintained only if spatial heterogeneity is strong, or, more interestingly, if the mimic is not too strongly distasteful. Therefore, mildly toxic species can become polymorphic in a wider range of ecological settings. Spatial dynamics thus reveal a region of Müllerian polymorphism separating classical Batesian polymorphism and Müllerian monomorphism along the mimic's palatability spectrum. Such polymorphism-palatability relationship in a spatial environment provides a parsimonious hypothesis accounting for the observed Müllerian polymorphism that does not require quasi-Batesian dynamics. While the stability of coexistence depends on all factors, only the migration rate and strength of selection appear to affect the level of diversity at the polymorphic equilibrium. Local adaptation is predicted in most polymorphic cases. These results are in very good accordance with recent empirical findings on the polymorphic butterflies Heliconius numata and H. cydno.
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Affiliation(s)
- Mathieu Joron
- Institut des Sciences de l'Evolution, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France.
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Morgan MT, Wilson WG. SELF-FERTILIZATION AND THE ESCAPE FROM POLLEN LIMITATION IN VARIABLE POLLINATION ENVIRONMENTS. Evolution 2005. [DOI: 10.1111/j.0014-3820.2005.tb01050.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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47
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Porcher E, Lande R. Reproductive compensation in the evolution of plant mating systems. THE NEW PHYTOLOGIST 2005; 166:673-684. [PMID: 15819929 DOI: 10.1111/j.1469-8137.2005.01363.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Reproductive compensation, the replacement of dead embryos by potentially viable ones, is known to play a major role in the maintenance of deleterious mutations in mammalian populations. However, it has received little attention in plant evolution. Here we model the joint evolution of mating system and inbreeding depression with reproductive compensation. We used a dynamic model of inbreeding depression, allowing for partial purging of recessive lethal mutations by selfing. We showed that reproductive compensation tended to increase the mean number of lethals in a population, but favored self-fertilization by effectively decreasing early inbreeding depression. When compensation depended on the selfing rate, stable mixed mating systems can occur, with low to intermediate selfing rates. Experimental evidence of reproductive compensation is required to confirm its potential importance in the evolution of plant mating systems. We suggest experimental methods to detect reproductive compensation.
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Affiliation(s)
- Emmanuelle Porcher
- Department of Biology, 0116, University of California - San Diego, La Jolla, CA 92093, USA
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48
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Roze D, Rousset F. Joint effects of self-fertilization and population structure on mutation load, inbreeding depression and heterosis. Genetics 2005; 167:1001-15. [PMID: 15238548 PMCID: PMC1470918 DOI: 10.1534/genetics.103.025148] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Both the spatial distribution of organisms and their mode of reproduction have important effects on the change in allele frequencies within populations. In this article, we study the combined effect of population structure and the rate of partial selfing of organisms on the efficiency of selection against recurrent deleterious mutations. Assuming an island model of population structure and weak selection, we express the mutation load, the within- and between-deme inbreeding depression, and heterosis as functions of the frequency of deleterious mutants in the metapopulation; we then use a diffusion model to calculate an expression for the equilibrium probability distribution of this frequency of deleterious mutants. This allows us to derive approximations for the average mutant frequency, mutation load, inbreeding depression, and heterosis, the simplest ones being Equations 35-39 in the text. We find that population structure can help to purge recessive deleterious mutations and reduce the load for some parameter values (in particular when the dominance coefficient of these mutations is <0.2-0.3), but that this effect is reversed when the selfing rate is above a given value. Conversely, within-deme inbreeding depression always decreases, while heterosis always increases, with the degree of population subdivision, for all selfing rates.
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Affiliation(s)
- Denis Roze
- Institut des Sciences de l'Evolution, Université Montpellier II, 34095 Montpellier, France.
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Trouve S, Degen L, Goudet J. Ecological components and evolution of selfing in the freshwater snail Galba truncatula. J Evol Biol 2005; 18:358-70. [PMID: 15715842 DOI: 10.1111/j.1420-9101.2004.00831.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reproductive assurance hypothesis emphasizes that self-fertilization should evolve in species with reduced dispersal capability, low population size or experiencing recurrent bottlenecks. Our work investigates the ecological components of the habitats colonized by the snail, Galba truncatula, that may influence the evolution of selfing. Galba truncatula is a preferential selfer inhabiting freshwater habitats, which vary with respect to the degree of permanence. We considered with a population genetic approach the spatial and the temporal degree of isolation of populations of G. truncatula. We showed that patches at distances of only a few meters are highly structured. The effective population sizes appear quite low, in the order of 10 individuals or less. This study indicates that individuals of the species G. truncatula are likely to be alone in a site and have a low probability of finding a partner from a nearby site to reproduce. These results emphasize the advantage of selfing in this species.
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Affiliation(s)
- S Trouve
- Department of Ecology and Evolution, Biology Building, University of Lausanne, Lausanne, Switzerland.
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50
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Porcher E, Lande R. The evolution of self-fertilization and inbreeding depression under pollen discounting and pollen limitation. J Evol Biol 2005; 18:497-508. [PMID: 15842479 DOI: 10.1111/j.1420-9101.2005.00905.x] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We model the evolution of plant mating systems under the joint effects of pollen discounting and pollen limitation, using a dynamic model of inbreeding depression, allowing for partial purging of recessive lethal mutations by selfing. Stable mixed mating systems occur for a wide range of parameter values with pollen discounting alone. However, when typical levels of pollen limitation are combined with pollen discounting, stable selfing rates are always high but less than 1 (0.9<s<1 in most cases); in this situation, complete selfing does not evolve because pollen discounting becomes very large at high selfing rates, so that the automatic advantage of selfing changes to a disadvantage. These results suggest that mixed mating systems with high selfing rates can be maintained by selection, whereas mixed mating systems with low to moderate selfing rates are more likely attributable to unavoidable geitonogamous selfing.
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Affiliation(s)
- E Porcher
- Department of Biology 0116, University of California, San Diego, La Jolla, CA 92093, USA.
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