| Autor: |
Hill P; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia., While GM; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia., Burridge CP; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia., Ezaz T; Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory 2601, Australia., Munch KL; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia., McVarish M; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia., Wapstra E; Discipline of Biological Sciences, University of Tasmania, Private Bag 5, Hobart, Tasmania 7000, Australia. |
| Abstrakt: |
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. |
