1
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Thonis A, Akçakaya HR. Experimental evidence that competition strength scales with ecological similarity: a case study using Anolis lizards. Oecologia 2024; 204:451-465. [PMID: 38244057 DOI: 10.1007/s00442-023-05507-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 12/18/2023] [Indexed: 01/22/2024]
Abstract
Interspecific competition is widely considered a powerful process underlying species coexistence and ecological community structure. Although coexistence theory predicts stronger competition between more ecologically similar species, empirical support has largely relied on inferring competition from patterns of species co-occurrence. Coexistence theory also posits that species can only coexist when individuals compete more with conspecifics than with other species, however, few field studies-particularly in reptiles-have simultaneously estimated the strength of both intra- and interspecific competition among co-occurring species. Using an array of 12 experimental plots, we manipulated species presence and population size by plot of three native Anolis lizard species to empirically estimate the strength of competition on one anole species driven by two other species of varying ecological similarity. We observed that the strength of competition-as determined by relative growth rates and gravidity-was highly predictable and correlated to ecological similarity. Interspecific competition was strongest among species of highest ecological similarity, and intraspecific competition-induced by the addition or removal of conspecifics-was consistently the most intense. By employing direct experimental manipulations, our study provides an empirical investigation of the strength of competition as it relates to ecological similarity.
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Affiliation(s)
- Anna Thonis
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, 11790, USA.
| | - H Reşit Akçakaya
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, 11790, USA
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2
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Stroud JT, Moore MP, Langerhans RB, Losos JB. Fluctuating selection maintains distinct species phenotypes in an ecological community in the wild. Proc Natl Acad Sci U S A 2023; 120:e2222071120. [PMID: 37812702 PMCID: PMC10589706 DOI: 10.1073/pnas.2222071120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 08/15/2023] [Indexed: 10/11/2023] Open
Abstract
Species' phenotypic characteristics often remain unchanged over long stretches of geological time. Stabilizing selection-in which fitness is highest for intermediate phenotypes and lowest for the extremes-has been widely invoked as responsible for this pattern. At the community level, such stabilizing selection acting individually on co-occurring species is expected to produce a rugged fitness landscape on which different species occupy distinct fitness peaks. However, even with an explosion of microevolutionary field studies over the past four decades, evidence for persistent stabilizing selection driving long-term stasis is lacking. Nonetheless, biologists continue to invoke stabilizing selection as a major factor explaining macroevolutionary patterns. Here, by directly measuring natural selection in the wild, we identified a complex community-wide fitness surface in which four Anolis lizard species each occupy a distinct fitness peak close to their mean phenotype. The presence of local fitness optima within species, and fitness valleys between species, presents a barrier to adaptive evolutionary change and acts to maintain species differences through time. However, instead of continuously operating stabilizing selection, we found that species were maintained on these peaks by the combination of many independent periods among which selection fluctuated in form, strength, direction, or existence and in which stabilizing selection rarely occurred. Our results suggest that lack of substantial phenotypic evolutionary change through time may be the result of selection, but not persistent stabilizing selection as classically envisioned.
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Affiliation(s)
- James T Stroud
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130
- Department of Biological Sciences, Florida International University, Miami, FL 33199
| | - Michael P Moore
- Department of Integrative Biology, University of Colorado Denver, Denver, CO 80217
| | - R Brian Langerhans
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695
| | - Jonathan B Losos
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130
- Living Earth Collaborative, Washington University in St. Louis, St. Louis, MO 63130
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3
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Warner DA, Kelly C, Pruett JE, Fargevieille A, Klabacka RL. Fluctuating environments hinder the ability of female lizards to choose suitable nest sites for their embryos. Behav Ecol Sociobiol 2023. [DOI: 10.1007/s00265-023-03310-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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4
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Effects of anthropogenic noise on cognition, bill color, and growth in the zebra finch (Taeniopygia guttata). Acta Ethol 2022. [DOI: 10.1007/s10211-022-00406-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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5
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Han B, Wei Q, Amiri E, Hu H, Meng L, Strand MK, Tarpy DR, Xu S, Li J, Rueppell O. The molecular basis of socially induced egg-size plasticity in honey bees. eLife 2022; 11:80499. [PMID: 36346221 PMCID: PMC9747152 DOI: 10.7554/elife.80499] [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: 05/23/2022] [Accepted: 11/07/2022] [Indexed: 11/11/2022] Open
Abstract
Reproduction involves the investment of resources into offspring. Although variation in reproductive effort often affects the number of offspring, adjustments of propagule size are also found in numerous species, including the Western honey bee, Apis mellifera. However, the proximate causes of these adjustments are insufficiently understood, especially in oviparous species with complex social organization in which adaptive evolution is shaped by kin selection. Here, we show in a series of experiments that queens predictably and reversibly increase egg size in small colonies and decrease egg size in large colonies, while their ovary size changes in the opposite direction. Additional results suggest that these effects cannot be solely explained by egg-laying rate and are due to the queens' perception of colony size. Egg-size plasticity is associated with quantitative changes of 290 ovarian proteins, most of which relate to energy metabolism, protein transport, and cytoskeleton. Based on functional and network analyses, we further study the small GTPase Rho1 as a candidate regulator of egg size. Spatio-temporal expression analysis via RNAscope and qPCR supports an important role of Rho1 in egg-size determination, and subsequent RNAi-mediated gene knockdown confirmed that Rho1 has a major effect on egg size in honey bees. These results elucidate how the social environment of the honey bee colony may be translated into a specific cellular process to adjust maternal investment into eggs. It remains to be studied how widespread this mechanism is and whether it has consequences for population dynamics and epigenetic influences on offspring phenotype in honey bees and other species.
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Affiliation(s)
- Bin Han
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China.,Department of Biology, University of North Carolina Greensboro, Greensboro, United States
| | - Qiaohong Wei
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Esmaeil Amiri
- Department of Biology, University of North Carolina Greensboro, Greensboro, United States.,Delta Research and Extension Center, Mississippi State University, Stoneville, United States
| | - Han Hu
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Lifeng Meng
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Micheline K Strand
- Biological and Biotechnology Sciences Branch, U.S. Army Research Office, DEVCOM-ARL, Baltimore, United States
| | - David R Tarpy
- Department of Applied Ecology, North Carolina State University, Raleigh, Canada
| | - Shufa Xu
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jianke Li
- Institute of Apicultural Research/Key Laboratory of Pollinating Insect Biology, Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Olav Rueppell
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
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6
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Sex-specific effects of capital resources on reproductive timing and success in red squirrels. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03245-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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Robinson SK, McChesney HM. Nesting success of red-winged blackbirds ( Agelaius phoeniceus) in marshes in an anthropogenic landscape. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220266. [PMID: 35911204 PMCID: PMC9326275 DOI: 10.1098/rsos.220266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Recent analyses show significant population declines in many abundant avian species, especially marsh-nesting species including the red-winged blackbird (RWBL). Hypothesized causes include reduced nesting success resulting from changing land-use patterns and exposure to contaminants. Our goal was to test the hypothesis that landscape and nest characteristics as well as exposure to polychlorinated biphenyls (PCBs) correlate with nesting success. From 2008 to 2014, we measured clutch size, egg and nestling mass, hatching and fledging success and daily survival of 1293 RWBL nests from 32 marshes in the Hudson River valley of New York. Using generalized linear effect and survival models, we found that: (i) Julian date was negatively related to hatching success and clutch size but positively related to egg mass; (ii) nest height was negatively related to hatching success; (iii) nestling mass decreased with increased nest density and distance to edges; (iv) fledging success was significantly lower in nests closer to the ground that were far from water; and (v) clutch size and daily survival were higher in nests farther from water. Results showed that nesting success was correlated with variables associated with flooding, population density and predation and provided no support for the predicted negative effects of PCB exposure.
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Affiliation(s)
- Scott K. Robinson
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA
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8
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Fargevieille A, Reedy AM, Kahrl AF, Mitchell TS, Durso AM, Delaney DM, Pearson PR, Cox RM, Warner DA. Propagule size and sex ratio influence colonisation dynamics after introduction of a non-native lizard. J Anim Ecol 2022; 91:845-857. [PMID: 35114034 DOI: 10.1111/1365-2656.13671] [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: 10/15/2021] [Accepted: 01/23/2022] [Indexed: 11/28/2022]
Abstract
The composition of founding populations plays an important role in colonisation dynamics and can influence population growth during early stages of biological invasion. Specifically, founding populations with small propagules (i.e., low number of founders) are vulnerable to the Allee effect and have reduced likelihood of establishment compared to those with large propagules. The founding sex ratio can also impact establishment via its influence on mating success and offspring production. Our goal was to test the effects of propagule size and sex ratio on offspring production and annual population growth following introductions of a non-native lizard species (Anolis sagrei). We manipulated propagule composition on nine small islands, then examined offspring production, population growth, and survival rate of founders and their descendants encompassing three generations. By the third reproductive season, per capita offspring production was higher on islands seeded with a relatively large propagule size, but population growth was not associated with propagule size. Propagule sex ratio did not affect offspring production, but populations with a female-biased propagule had positive growth, whereas those with a male-biased propagule had negative growth in the first year. Populations were not affected by propagule sex ratio in subsequent years, possibly due to rapid shifts towards balanced (or slightly female-biased) population sex ratios. Overall, we show that different components of population fitness have different responses to propagule size and sex ratio in ways that could affect early stages of biological invasion. Despite these effects, the short lifespan and high fecundity of A. sagrei likely helped small populations to overcome Allee effects and enabled all populations to successfully establish. Our rare experimental manipulation of propagule size and sex ratio can inform predictions of colonisation dynamics in response to different compositions of founding populations, which is critical in the context of population ecology and invasion dynamics.
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Affiliation(s)
- Amélie Fargevieille
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.,Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | - Aaron M Reedy
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.,Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA
| | - Ariel F Kahrl
- Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA.,Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg, 18B SE-10691, Stockholm, Sweden
| | - Timothy S Mitchell
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.,Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, 50011, USA.,Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA
| | - Andrew M Durso
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, FL, 33965, USA
| | - David M Delaney
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, 50011, USA.,Department of Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, Colorado, 80302, USA
| | - Phillip R Pearson
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.,Department of Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Centre for Conservation, Ecology and Genomics, University of Canberra, Bruce, ACT, 2617, Australia
| | - Robert M Cox
- Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA
| | - Daniel A Warner
- Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.,Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, 50011, USA.,Department of Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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9
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Pruett JE, Warner DA. Spatial and temporal variation in phenotypes and fitness in response to developmental thermal environments. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13910] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Jenna E. Pruett
- Department of Biological Sciences Auburn University Auburn Alabama USA
| | - Daniel A. Warner
- Department of Biological Sciences Auburn University Auburn Alabama USA
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10
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Hall JM, Miracle J, Scruggs CD, Warner DA. Natural nest substrates influence squamate embryo physiology but have little effect on hatchling phenotypes. Integr Zool 2021; 17:550-566. [PMID: 34002932 DOI: 10.1111/1749-4877.12553] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vertebrate embryos require access to water; however, many species nest in terrestrial habitats that vary considerably in moisture content. Oviparous, non-avian reptiles have served as models to understand how environmental factors, like moisture availability, influence development because eggs are often exposed to prevailing environments in the absence of parental care. Though much research demonstrates the importance of water absorption by eggs, many ecological factors that influence moisture availability in natural nests have received little attention. For example, the type of substrate in which nests are constructed is understudied. We experimentally incubated eggs of the brown anole lizard (Anolis sagrei) in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations. One substrate consisted of sand and crushed seashells and the other was mostly organic material (i.e. decayed plant material). Both are common nesting substrates at our field site. When controlling for water uptake by eggs, we found that egg survival and hatchling phenotypes were similar between substrates; however, embryos developed more quickly in the sand/shell substrate than the organic substrate, indicating substrate-specific effects on embryo physiology. These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable; however, some aspects of development, like developmental rate, are affected by the type of substrate, independent of water availability. Further study is required to determine how natural substrates influence embryo physiology independent of water content.
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Affiliation(s)
- Joshua M Hall
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
| | - Jocelyn Miracle
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
| | - Cindy D Scruggs
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
| | - Daniel A Warner
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
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11
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Pandit MM, Eapen J, Pineda-Sabillon G, Caulfield ME, Moreno A, Wilhelm J, Ruyle JE, Bridge ES, Proppe DS. Anthropogenic noise alters parental behavior and nestling developmental patterns, but not fledging condition. Behav Ecol 2021. [DOI: 10.1093/beheco/arab015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Abstract
Anthropogenic noise is a ubiquitous feature of the American landscape, and is a known stressor for many bird species, leading to negative effects in behavior, physiology, reproduction, and ultimately fitness. While a number of studies have examined how anthropogenic noise affects avian fitness, there are few that simultaneously examine how anthropogenic noise impacts the relationship between parental care behavior and nestling fitness. We conducted Brownian noise playbacks for 6 h a day during the nesting cycle on Eastern Bluebird (Sialia sialis) nest boxes to investigate if experimentally elevated noise affected parental care behavior, nestling body conditions, and nestling stress indices. We documented nest attendance by adult females using radio frequency identification (RFID), and we assessed nestling stress by measuring baseline corticosterone levels and telomere lengths. Based on the RFID data collected during individual brood cycles, adult bluebirds exposed to noise had significantly higher feeding rates earlier in the brood cycle than adults in the control group, but reduced feeding rates later in the cycle. Nestlings exposed to noise had higher body conditions than the control nestlings at 11 days of age, but conditions equalized between treatments by day 14. We found no differences in nestling baseline corticosterone levels or nestling telomere lengths between the two treatment groups. Our results revealed that noise altered adult behavior, which corresponded with altered nestling body condition. However, the absence of indicators of longer-term effects of noise on offspring suggests adult behavior may have been a short-term response.
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Affiliation(s)
- Meelyn Mayank Pandit
- Department of Biology, University of Oklahoma, Norman, OK, USA
- Oklahoma Biological Survey, University of Oklahoma, Norman, OK, USA
| | - James Eapen
- Biology Department, Calvin University, SE, Grand Rapids, MI, USA
| | | | - Margaret E Caulfield
- Biology Department, Calvin University, SE, Grand Rapids, MI, USA
- MSU College of Human Medicine, Grand Rapids Research Center, The Department of Translational Neuroscience, NW, Grand Rapids, MI, USA
| | - Alexander Moreno
- School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA
- Advanced Radar Research Center, University of Oklahoma, Norman, OK, USA
| | - Jay Wilhelm
- Russ College of Engineering and Technology, Ohio University, Stocker Center, Athens, OH, USA
| | - Jessica E Ruyle
- School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA
- Advanced Radar Research Center, University of Oklahoma, Norman, OK, USA
| | - Eli S Bridge
- Department of Biology, University of Oklahoma, Norman, OK, USA
- Oklahoma Biological Survey, University of Oklahoma, Norman, OK, USA
| | - Darren S Proppe
- Biology Department, Calvin University, SE, Grand Rapids, MI, USA
- Wild Basin Creative Research Center, Austin, TX, USA
- School of Natural Sciences, St. Edwards University, Austin, TX, USA
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12
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Li S, Hao X, Sun B, Bi J, Zhang Y, DU W. Phenotypic consequences of maternally selected nests: a cross-fostering experiment in a desert lizard. Integr Zool 2020; 16:741-754. [PMID: 33190392 DOI: 10.1111/1749-4877.12505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Despite the importance of maternally selected nests in shaping offspring phenotypes, our understanding of how the nest environment affects embryonic development and offspring traits of most non-avian reptiles is rather limited largely due to the logistical difficulty in locating their nests. To identify the relative contributions of environmental (temporal [seasonal] and spatial [nest-site]) and intrinsic (clutch) factors on embryonic development and offspring traits, we conducted a cross-fostering experiment by swapping eggs between maternally-selected nests of the toad-headed agama (Phrynocephalus przewalskii) in the field. We found that nest environment explained a large proportion of variation in incubation duration, hatching success, and offspring size and growth. In contrast, clutch only explained a small proportion of variation in these embryonic and offspring traits. More significantly, compared with spatial effects, seasonal effects explained more phenotypic variation in both embryonic development and offspring traits. Eggs laid early in the nesting season had longer incubation durations and produced smaller hatchlings with higher post-hatching growth rates than did later-laid eggs. Consequently, hatchlings from early-laid eggs reached larger body sizes prior to winter. In addition, we found that female toad-headed agama did not select nests specific to reaction norms of their own offspring because hatchlings from original or translocated nests had similar phenotypic traits. Overall, our study demonstrates the importance of seasonal variation in nest environments in determining embryonic development and offspring phenotypes, which has not been widely appreciated at least in non-avian reptiles.
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Affiliation(s)
- Shuran Li
- College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang, China.,International Society of Zoological Sciences, Beijing, China
| | - Xin Hao
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Baojun Sun
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Junhuai Bi
- College of Life Science, Inner Mongolia Normal University, Hohhot, Inner Mongolia, China
| | - Yongpu Zhang
- College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang, China
| | - Weiguo DU
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
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13
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Dependence on a human structure influences the extinction of a non-native lizard population after a major environmental change. Biol Invasions 2020. [DOI: 10.1007/s10530-020-02405-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Hall JM, Warner DA. Ecologically relevant thermal fluctuations enhance offspring fitness: biological and methodological implications for studies of thermal developmental plasticity. J Exp Biol 2020; 223:jeb231902. [PMID: 32778564 DOI: 10.1242/jeb.231902] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 08/04/2020] [Indexed: 08/26/2023]
Abstract
Natural thermal environments are notably complex and challenging to mimic in controlled studies. Consequently, our understanding of the ecological relevance and underlying mechanisms of organismal responses to thermal environments is often limited. For example, studies of thermal developmental plasticity have provided key insights into the ecological consequences of temperature variation, but most laboratory studies use treatments that do not reflect natural thermal regimes. While controlling other important factors, we compared the effects of naturally fluctuating temperatures with those of commonly used laboratory regimes on development of lizard embryos and offspring phenotypes and survival. We incubated eggs in four treatments: three that followed procedures commonly used in the literature, and one that precisely mimicked naturally fluctuating nest temperatures. To explore context-dependent effects, we replicated these treatments across two seasonal regimes: relatively cool temperatures from nests constructed early in the season and warm temperatures from late-season nests. We show that natural thermal fluctuations have a relatively small effect on developmental variables but enhance hatchling performance and survival at cooler temperatures. Thus, natural thermal fluctuations are important for successful development and simpler approximations (e.g. repeated sine waves, constant temperatures) may poorly reflect natural systems under some conditions. Thus, the benefits of precisely replicating real-world temperatures in controlled studies may outweigh logistical costs. Although patterns might vary according to study system and research goals, our methodological approach demonstrates the importance of incorporating natural variation into controlled studies and provides biologists interested in thermal ecology with a framework for validating the effectiveness of commonly used methods.
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Affiliation(s)
- Joshua M Hall
- Auburn University, Department of Biological Sciences, 101 Rouse Life Sciences Building, Auburn, AL 36849, USA
| | - Daniel A Warner
- Auburn University, Department of Biological Sciences, 101 Rouse Life Sciences Building, Auburn, AL 36849, USA
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15
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Hall JM, Sun BJ. Heat tolerance of reptile embryos: Current knowledge, methodological considerations, and future directions. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 335:45-58. [PMID: 32757379 DOI: 10.1002/jez.2402] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/17/2020] [Accepted: 07/22/2020] [Indexed: 12/12/2022]
Abstract
Aspects of global change result in warming temperatures that threaten biodiversity across the planet. Eggs of non-avian, oviparous reptiles (henceforth "reptiles") are particularly vulnerable to warming due to a lack of parental care during incubation and limited ability to behaviorally thermoregulate. Because warming temperatures will cause increases in both mean and variance of nest temperatures, it is crucial to consider embryo responses to both chronic and acute heat stress. Although many studies have considered embryo survival across constant incubation temperatures (i.e., chronic stress) and in response to brief exposure to extreme temperatures (i.e., acute stress), there are no standard metrics or terminology for determining heat stress of embryos. This impedes comparisons across studies and species and hinders our ability to predict how species will respond to global change. In this review, we compare various methods that have been used to assess embryonic heat tolerance in reptiles and provide new terminology and metrics for quantifying embryo responses to both chronic and acute heat stress. We apply these recommendations to data from the literature to assess chronic heat tolerance in 16 squamates, 16 turtles, five crocodilians, and the tuatara and acute heat tolerance for nine squamates and one turtle. Our results indicate that there is relatively large variation in chronic and acute heat tolerance across species, and we outline directions for future research, calling for more studies that assess embryo responses to acute thermal stress, integrate embryo responses to chronic and acute temperatures in predictive models, and identify mechanisms that determine heat tolerance.
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Affiliation(s)
- Joshua M Hall
- Department of Biological Sciences, Auburn University, Auburn, Alabama
| | - Bao-Jun Sun
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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16
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DeSana A, Fargevieille A, Warner DA. Survival of lizard eggs varies with microhabitat in the presence of an invertebrate nest predator. Evol Ecol 2020. [DOI: 10.1007/s10682-020-10058-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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