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Silver‐Gorges I, Shamblin BM, Ashford M, Bower P, Fuentes MMPB. Potential drivers and implications of a balanced breeding sex ratio in a small population of an imperiled species with environmental sex determination. Ecol Evol 2024; 14:e70166. [PMID: 39224154 PMCID: PMC11366973 DOI: 10.1002/ece3.70166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Revised: 07/24/2024] [Accepted: 07/29/2024] [Indexed: 09/04/2024] Open
Abstract
Small populations of imperiled species are susceptible to the negative consequences of skewed sex-ratios. In imperiled species with environmental sex determination such as sea turtles, examining sex ratios across a range of environments and population abundance levels can provide insight into factors that influence population resilience, which can then be the foci of management plans for these species. Breeding sex ratios (the ratio of actively breeding males to females during a reproductive season; BSRs) extrapolated from genetic parentage analyses are a common approach for enumerating sex ratios in sea turtles. Such analyses also allow for the characterization of multiple paternity within sea turtle clutches, which should reflect BSRs and breeding behaviors. We characterized the first BSR for a breeding assemblage of loggerhead sea turtles (Caretta caretta) belonging to the temperate, low-abundance Northern Gulf of Mexico Recovery Unit using genotypes of 16 microsatellite loci from nesting females and hatchlings. Unlike prior studies at both more-tropical and more-temperate, and higher-abundance, Recovery Units in this region, we found a balanced BSR of 1.3:1 males:female and a low incidence (~17%) of multiple paternity. This suggests that there are relatively few males breeding at this assemblage and within this Recovery Unit. Beaches in this region are expected to produce substantial numbers of male hatchlings based on sand temperature data. The relative dearth of mature males may then be due to hydrologic disturbances that disproportionately affect the fitness and survival of male hatchlings, or due to demographic stochasticity. More work is needed to study the factors that might influence male hatchling production and fitness in this region, particularly as climate change is predicted to lead to feminization in global sea turtle populations. Our work demonstrates the broad utility of characterizing BSRs and other sex ratios across a range of populations in imperiled, environmentally sensitive species.
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Affiliation(s)
- Ian Silver‐Gorges
- Department of Earth, Ocean, and Atmospheric ScienceFlorida State UniversityTallahasseeFloridaUSA
| | - Brian M. Shamblin
- Warnell School of Forestry and Natural ResourcesUniversity of GeorgiaAthensGeorgiaUSA
| | - Mason Ashford
- Department of Earth, Ocean, and Atmospheric ScienceFlorida State UniversityTallahasseeFloridaUSA
| | - Paityn Bower
- Department of Earth, Ocean, and Atmospheric ScienceFlorida State UniversityTallahasseeFloridaUSA
| | - Mariana M. P. B. Fuentes
- Department of Earth, Ocean, and Atmospheric ScienceFlorida State UniversityTallahasseeFloridaUSA
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Debruyn G, Geltmeyer J, Schoolaert E, Nicolaï MPJ, Xie W, Wynant M, Shawkey MD, De Clerck K, D'Alba L. Hydric Environment and Chemical Composition Shape Non-avian Reptile Eggshell Absorption. Integr Comp Biol 2024; 64:107-119. [PMID: 38755009 DOI: 10.1093/icb/icae040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 04/19/2024] [Accepted: 05/06/2024] [Indexed: 05/18/2024] Open
Abstract
The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution. Here, we first performed histology, Fourier-transform infrared spectroscopy and dynamic vapor sorption experiments to elucidate the mechanisms of eggshell absorption for 56 reptile species. Then, we used phylogenetic comparative analysis to test the hypothesis that the absorptive capacity of reptile eggshells increases with aridity of the environment. We found that water absorption increases in the presence of a superficial mucopolysaccharide layer and decreases with increased calcium content. We found that eggs from arid environments have highly absorbent eggshells, but only in species with weakly calcified shells. Our results suggest that reptile eggshells have over evolutionary time tuned absorptive capacity to environmental moisture level. Since these eggs often must sustain conflicting constraints, they may serve as inspirations for new biomimetic materials, such as water filtering membranes or humidity sensors.
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Affiliation(s)
- Gerben Debruyn
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Jozefien Geltmeyer
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Ella Schoolaert
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Michaël P J Nicolaï
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Wanjie Xie
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Maarten Wynant
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Matthew D Shawkey
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Karen De Clerck
- Center for Textile Science and Engineering, Faculty of Engineering and Architecture, University of Ghent, Tech Lane Science Park 701, B-9052 Ghent, Belgium
| | - Liliana D'Alba
- Department of Biology, Evolution and Optics of Nanostructures Group, University of Ghent, Ledeganckstraat 35, 9000 Ghent, Belgium
- Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
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Cordero GA, Balk ML, Pérez-González CE, Solberg LM, Doody JS, Plummer MV, Janzen FJ. Geographic variation in incubation temperatures promoting viable offspring production in broadly co-distributed turtles. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2024; 341:509-524. [PMID: 38436056 DOI: 10.1002/jez.2802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 02/09/2024] [Accepted: 02/12/2024] [Indexed: 03/05/2024]
Abstract
Organisms whose early life stages are environmentally sensitive produce offspring within a relatively narrow range of suitable abiotic conditions. In reptiles, development rate and survival are often maximized if incubation temperatures remain under 31°C, though this upper bound may vary within and among species. We addressed this expectation by comparing responses to egg incubation at 30°C versus 33°C in congeneric turtle species pairs with broad syntopic geographic distributions. In the two softshell turtles (Apalone spp.), the greatest changes in development rate and phenotypic variance were observed in the northernmost population, which had a low survival rate (40%) at 33°C. The presumably suboptimal temperature (33°C) for northern populations otherwise yielded 76%-93% survival rates and fast swimming speeds in more southern populations. Still, in one species, northern hatchlings incubated at 33°C matched the elevated speeds of their southern counterparts, revealing a countergradient response. In northern populations of the two map turtles (Graptemys spp.), survival was also reduced (28%-60%) at 33°C and the development rate (relative to 30°C) increased by up to 75%. Our experiments on divergent taxa with similar nesting ecologies substantiate that the optimal thermal range for offspring production is variable. These findings encourage further work on how population- and species-level differences relate to local adaptation in widely distributed oviparous species.
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Affiliation(s)
- Gerardo A Cordero
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - Michelle L Balk
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - César E Pérez-González
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - Lisa M Solberg
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - Jeremiah Sean Doody
- Department of Integrative Biology, University of South Florida-St. Petersburg, St. Petersburg, Florida, USA
| | | | - Fredric J Janzen
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
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Du WG, Li SR, Sun BJ, Shine R. Can nesting behaviour allow reptiles to adapt to climate change? Philos Trans R Soc Lond B Biol Sci 2023; 378:20220153. [PMID: 37427463 PMCID: PMC10331901 DOI: 10.1098/rstb.2022.0153] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/18/2023] [Indexed: 07/11/2023] Open
Abstract
A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.
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Affiliation(s)
- Wei-Guo Du
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Shu-Ran Li
- College of Life and Environmental Science, Wenzhou University, Zhejiang 325035, People's Republic of China
| | - Bao-Jun Sun
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Richard Shine
- School of Natural Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
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Gatto CR, Williamson SA, Reina RD. Mitigating the effects of climate change on the nests of sea turtles with artificial irrigation. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2023; 37:e14044. [PMID: 36661082 PMCID: PMC10108123 DOI: 10.1111/cobi.14044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 09/28/2022] [Accepted: 10/06/2022] [Indexed: 06/17/2023]
Abstract
For sea turtles, like many oviparous species, increasing temperatures during development threaten to increase embryonic mortality, alter offspring quality, and potentially create suboptimal primary sex ratios. Various methods are being implemented to mitigate the effects of climate change on reproductive success, but these methods, such as breeding programs, translocations, and shading, are often invasive and expensive. Irrigation is an alternative strategy for cooling nests that, depending on location, can be implemented relatively quickly and cheaply. However, multiple factors, including ambient conditions, nest substrate, and species characteristics, can influence irrigation success. Additionally, irrigation can vary in duration, frequency, and the volume of water applied to nests, which influences the cooling achieved and embryonic survival. Thus, it is critical to understand how to maximize cooling and manage risks before implementing irrigation as a nest-cooling strategy. We reviewed the literature on nest irrigation to examine whether artificial irrigation is feasible as a population management tool. Key factors that affected cooling were the volume of water applied and the frequency of applications. Embryonic responses varied with species, ambient conditions, and the timing of irrigation during development. Nest inundation was the key risk to a successful irrigation regime. Future irrigation regimes must identify clear targets, either primary or adult sex ratios, that maximize population viability. Monitoring population responses and adjusting the irrigation regime in response to population characteristics will be critical. Most studies reported on the manipulation of only one or two variables, further research is required to understand how altering multiple factors in an irrigation regime influences the cooling achieved and embryonic responses.
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Affiliation(s)
| | - Sean A. Williamson
- School of Biological SciencesFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Richard D. Reina
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
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Booth DT, Staines MN, Reina RD. Sand characteristics do not influence hatching success of nests at the world’s largest green turtle rookery. AUST J ZOOL 2022. [DOI: 10.1071/zo21050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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