Pleistocene divergence in the absence of gene flow among populations of a viviparous reptile with intraspecific variation in sex determination

Hill, Peta; Wapstra, Erik; Ezaz, Tariq; Burridge, Christopher P.

doi:10.1002/ece3.7458

Cited by 8 publications

(4 citation statements)

References 78 publications

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“…Cold‐induced telomere shortening may be explained, in part, by increased ROS in the cold basking treatment or increased telomerase expression, or increasing antioxidant activity/efficiency in the hot basking treatment. The lack of a population effect is surprising given that the populations are genetically isolated (Hill et al, 2021), with ample evidence of local adaptation to thermal conditions in their physiology, behaviour and reproduction (Cadby et al, 2014; Caldwell et al, 2017; Yuni, 2016; Yuni et al, 2015). Further work needs to carefully consider potential ontogenetic and/or acclimation effects that can occur rapidly in both the wild and in the laboratory and can confound interpretation of population‐specific divergence and adaptive inferences.…”

Section: Thermal Effects At the Level Of The Cell: Links To Telomere ...mentioning

confidence: 99%

Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals

2021

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Ectotherms are classic models for understanding life‐history tradeoffs, including the reproduction–somatic maintenance tradeoffs that may be reflected in telomere length and their dynamics. Importantly, life‐history traits of ectotherms are tightly linked to their thermal environment, with diverse or synergistic mechanistic explanations underpinning the variation. Telomere dynamics potentially provide a mechanistic link that can be used to monitor thermal effects on individuals in response to climatic perturbations. Growth rate, age and developmental stage are all affected by temperature, which interacts with telomere dynamics in complex and intriguing ways. The physiological processes underpinning telomere dynamics can be visualized and understood using thermal performance curves (TPCs). TPCs reflect the evolutionary history and the thermal environment during an individual's ontogeny. Telomere maintenance should be enhanced at or near the thermal performance optimum of a species, population and individual. The thermal sensitivity of telomere dynamics should reflect the interacting TPCs of the processes underlying them. The key processes directly underpinning telomere dynamics are mitochondrial function (reactive oxygen production), antioxidant activity, telomerase activity and telomere endcap protein status. We argue that identifying TPCs for these processes will significantly help design robust, repeatable experiments and field studies of telomere dynamics in ectotherms. Conceptually, TPCs are a valuable framework to predict and interpret taxon‐ and population‐specific telomere dynamics across thermal regimes. The literature of thermal effects on telomeres in ectotherms is sparse and mostly limited to vertebrates, but our conclusions and recommendations are relevant across ectothermic animals.

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Section: Thermal Effects At the Level Of The Cell: Links To Telomere ...mentioning

confidence: 99%

Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals

2021

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“…4) established a potential adaptive explanation for the intraspecific variation in sex determination in C. ocellatus, but its mechanistic predictions (emergence/loss of genes of major effect at high/low elevation) require testing. Sex chromosomes and sex-linked DNA in C. ocellatus differ only slightly between the populations (Hill et al 2018(Hill et al , 2021a) and these populations diverged during the Pleistocene with negligible gene flow since divergence (Hill et al 2021b). Specifically, and in contrast to some of the model predictions, both populations have XY heterogamety with morphologically undifferentiated X and Y sex chromosomes (Hill et al 2021a) (Fig.…”

Section: An Australian Model System For Transitions In Sex Determination: Carinascincus Ocellatusmentioning

confidence: 86%

Australian lizards are outstanding models for reproductive biology research

et al. 2021

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Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

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“…Gene flow of GSD genotypes into a population can inhibit its transition to TSD [ 59 ]. While gene flow between high- and low-elevation C. ocellatus populations is negligible [ 60 , 61 ], GSD genotypes could enter the low-elevation population from more proximate sources and thus attenuate a transition to TSD. Heritable variation in the threshold for sex reversal also decreases the likelihood of a transition to TSD because the maintenance of variation in the sex reversal threshold across generations will favour the persistence of a mixed system of sex determination [ 59 ].…”

Section: Discussionmentioning

confidence: 99%

Sex reversal explains some, but not all, climate-mediated sex ratio variation within a viviparous reptile

et al. 2022

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Evolutionary transitions in sex-determining systems have occurred frequently yet understanding how they occur remains a major challenge. In reptiles, transitions from genetic to temperature-dependent sex determination can occur if the gene products that determine sex evolve thermal sensitivity, resulting in sex-reversed individuals. However, evidence of sex reversal is limited to oviparous reptiles. Here we used thermal experiments to test whether sex reversal is responsible for differences in sex determination in a viviparous reptile, Carinascincus ocellatus, a species with XY sex chromosomes and population-specific sex ratio response to temperature. We show that sex reversal is occurring and that its frequency is related to temperature. Sex reversal was unidirectional (phenotypic males with XX genotype) and observed in both high- and low-elevation populations. We propose that XX-biased genotypic sex ratios could produce either male- or female-biased phenotypic sex ratios as observed in low-elevation C. ocellatus under variable rates of XX sex reversal. We discuss reasons why sex reversal may not influence sex ratios at high elevation. Our results suggest that the mechanism responsible for evolutionary transitions from genotypic to temperature-dependent sex determination is more complex than can be explained by a single process such as sex reversal.

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Pleistocene divergence in the absence of gene flow among populations of a viviparous reptile with intraspecific variation in sex determination

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 8 publications

References 78 publications

Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals

Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals

Australian lizards are outstanding models for reproductive biology research

Sex reversal explains some, but not all, climate-mediated sex ratio variation within a viviparous reptile

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