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

Peta Hill, Geoffrey M. While, Christopher P. Burridge, MD Tariq Ezaz, Kirke Munch, Mary McVarish, Erik Wapstra

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Volume289
Issue number1976
DOIs
Publication statusPublished - 12 May 2022

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