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Straková B, Kubička L, Červenka J, Kratochvíl L. Pivotal temperature is not for everyone: Evidence for temperature-dependent sex determination in three gecko species. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2024; 341:597-605. [PMID: 38497303 DOI: 10.1002/jez.2808] [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: 11/01/2023] [Revised: 02/20/2024] [Accepted: 02/23/2024] [Indexed: 03/19/2024]
Abstract
The prevalence of environmental sex determination (ESD) in squamate reptiles is often overestimated in the literature. This is surprising because we have reliable data demonstrating ESD in only a few species. The documentation of ESD in three species of geckos presented here has significantly increased our knowledge, given that satisfactory evidence for ESD existed in only eight other gecko species. For the first time, we document the occurrence of ESD in the family Sphaerodactylidae. Our finding of unexpected variability in the shapes of reaction norms among geckos highlights that traditional descriptions using parameters such as pivotal temperature, that is, temperature producing a 50:50 sex ratio, are unsatisfactory. For example, the gecko Pachydactylus tigrinus lacks any pivotal temperature and its sex ratios are strongly female-biased across the entire range of viable temperatures. We argue for the effective capture of the relationship between temperature and sex ratio using specific nonlinear models rather than using classical simplistic descriptions and classifications of reaction norms.
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Affiliation(s)
- Barbora Straková
- Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Lukáš Kubička
- Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Jan Červenka
- Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Lukáš Kratochvíl
- Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic
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Holt WV, Comizzoli P. Conservation Biology and Reproduction in a Time of Developmental Plasticity. Biomolecules 2022; 12:1297. [PMID: 36139136 PMCID: PMC9496186 DOI: 10.3390/biom12091297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/11/2022] [Accepted: 09/12/2022] [Indexed: 11/24/2022] Open
Abstract
The objective of this review is to ask whether, and how, principles in conservation biology may need to be revisited in light of new knowledge about the power of epigenetics to alter developmental pathways. Importantly, conservation breeding programmes, used widely by zoological parks and aquariums, may appear in some cases to reduce fitness by decreasing animals' abilities to cope when confronted with the 'wild side' of their natural habitats. Would less comfortable captive conditions lead to the selection of individuals that, despite being adapted to life in a captive environment, be better able to thrive if relocated to a more natural environment? While threatened populations may benefit from advanced reproductive technologies, these may actually induce undesirable epigenetic changes. Thus, there may be inherent risks to the health and welfare of offspring (as is suspected in humans). Advanced breeding technologies, especially those that aim to regenerate the rarest species using stem cell reprogramming and artificial gametes, may also lead to unwanted epigenetic modifications. Current knowledge is still incomplete, and therefore ethical decisions about novel breeding methods remain controversial and difficult to resolve.
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Affiliation(s)
- William V. Holt
- Department of Oncology & Metabolism, The Medical School Beech Hill Road, Sheffield S10 2RX, UK
| | - Pierre Comizzoli
- Smithsonian’s National Zoo and Conservation Biology Institute, Washington, DC 20008, USA
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Plaisir CA, King WJ, Forsyth DM, Festa-Bianchet M. Effects of rainfall, forage biomass, and population density, on survival and growth of juvenile kangaroos. J Mammal 2022. [DOI: 10.1093/jmammal/gyab132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
A central goal of ecology is to understand how environmental variation affects populations. Long-term studies of marked individuals can quantify the effects of environmental variation on key life-history traits. We monitored the survival and growth of 336 individually marked juvenile eastern grey kangaroos (Macropus giganteus), a large herbivore living in a seasonal but unpredictable environment. During our 12-year study, the population experienced substantial variation in rainfall, forage biomass, and density. We used structural equation modeling to determine how variation in temperature and rainfall affected juvenile survival and growth through its effect on forage biomass and population density. Independently of population density, forage biomass had strong positive effects on survival from 10 to 21 months. At low population density, forage biomass also had a positive effect on skeletal growth to 26 months. Increasing maternal body condition improved rearing success for daughters but not for sons. High population density reduced skeletal growth to 26 months for both sexes. Rainfall had an increasingly positive effect on forage biomass at high temperatures, indicating a seasonal effect on food availability. Our study reveals interacting effects of environmental variation on juvenile survival and growth for a large mammal with a conservative reproductive strategy that experiences substantial stochasticity in food availability.
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Affiliation(s)
- Charles-Alexandre Plaisir
- Département de Biologie, Université de Sherbrooke, 2500, Boulevard de l’Université, Sherbrooke, QC J1K 2R1, Canada
| | - Wendy J King
- Département de Biologie, Université de Sherbrooke, 2500, Boulevard de l’Université, Sherbrooke, QC J1K 2R1, Canada
- Research School of Biology, Australian National University, 134, Linnaeus Way, Acton, ACT 2601, Australia
| | - David M Forsyth
- Vertebrate Pest Research Unit, NSW Department of Primary Industries, 1447 Forest Road, Orange, NSW 2800, Australia
- School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Marco Festa-Bianchet
- Département de Biologie, Université de Sherbrooke, 2500, Boulevard de l’Université, Sherbrooke, QC J1K 2R1, Canada
- Research School of Biology, Australian National University, 134, Linnaeus Way, Acton, ACT 2601, Australia
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Barra T, Viblanc VA, Saraux C, Murie JO, Dobson FS. Parental investment in the Columbian ground squirrel: empirical tests of sex allocation models. Ecology 2021; 102:e03479. [PMID: 34270793 DOI: 10.1002/ecy.3479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 05/04/2021] [Accepted: 05/19/2021] [Indexed: 11/09/2022]
Abstract
Parental allocation of resources into male or female offspring and differences in the balance of offspring sexes in natural populations are central research topics in evolutionary ecology. Fisher (Fisher, R. A. 1930. The genetical theory of natural selection, Clarendon Press, Oxford, UK) identified frequency-dependent selection as the mechanism responsible for an equal investment in the sexes of offspring at the end of parental care. Three main theories have been proposed for explaining departures from Fisherian sex ratios in light of variation in environmental (social) and individual (maternal condition) characteristics. The Trivers-Willard model (Trivers, R., and D. Willard. 1973. Natural selection of parental ability to vary the sex ratio of offspring. Science 179:90-92) of male-biased sex allocation by mothers in the best body condition is based on the competitive ability of male offspring for future access to mates and thus superior reproduction. The local resource competition model is based on competitive interactions in matrilines, as occur in many mammal species, where producing sons reduces future intrasexual competition with daughters. A final model invokes advantages of maintaining matrilines for philopatric females, despite any increased competition among females. We used 29 yr of pedigree and demographic data to evaluate these hypotheses in the Colombian ground squirrel (Urocitellus columbianus), a semisocial species characterized by strong female philopatry. Overall, male offspring were heavier than female offspring at birth and at weaning, suggesting a higher production cost. With more local kin present, mothers in the best condition biased their offspring sex ratio in favor of males, and mothers in poor condition biased offspring sex ratio in favor of females. Without co-breeding close kin, the pattern was reversed, with mothers in the best condition producing more daughters, and mothers in poor condition producing more sons. Our results do not provide strong support for any of the single-factor models of allocation to the sexes of offspring, but rather suggest combined influences of relative maternal condition and matriline dominance on offspring sex ratio.
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Affiliation(s)
- Thibaut Barra
- Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, UMR 7178, Strasbourg, 67000, France
| | - Vincent A Viblanc
- Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, UMR 7178, Strasbourg, 67000, France
| | - Claire Saraux
- Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, UMR 7178, Strasbourg, 67000, France
| | - Jan O Murie
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada
| | - F Stephen Dobson
- Institut Pluridisciplinaire Hubert Curien, University of Strasbourg, CNRS, UMR 7178, Strasbourg, 67000, France.,Department of Biological Sciences, Auburn University, 311 Funchess Hall, Auburn, Alabama, 36849, USA
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