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bioRxiv · 10.1101/2024.11.17.624031

Demographic pathways linking sex-chromosome system to adult sex ratio variation across tetrapods

Pipoly, I.·Bokony, V.·Gaillard, J.-M.·Lemaitre, J.-F.·Szekely, T.·Liker, A.
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Abstract

Sex chromosomes determine male and female phenotypes, and the resulting sex differences can have significant impacts on ecology and life history. One manifestation of this link is that ZZ/ZW sex-determination systems are associated with more male-skewed adult sex ratio (ASR, proportion of males in the adult population) than XY/XX systems across tetrapods (amphibians, reptiles, birds, and mammals). Here we investigate four demographic processes: male and female offspring production, sex differences in juvenile and adult mortalities and in timing of maturation that can contribute to ASR variation between XY/XX and ZZ/ZW systems, using phylogenetic analyses of a large dataset collected from tetrapod species in the wild. We show that sex differences in adult mortality reliably predict ASR, and it is also more male-biased in XY/XX species than in ZZ/ZW species. Sex differences in juvenile mortality or in maturation time also contribute to ASR skews, but do not differ consistently between XY/XX and ZZ/ZW systems. Phylogenetic path analyses confirm an influence of sex-determination system on ASR through sex-biased adult mortality. Thus, these results infer that sex chromosomes can impact, via demographic pathways, frequency-dependent selection emerging from the relative number of males and females. We call for follow-up studies to uncover the potentially complex web of associations between sex determination, population dynamics, and social behaviour.

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Pipoly, I., Bokony, V., Gaillard, J.-M., Lemaitre, J.-F., Szekely, T., Liker, A.. 2024-11-18. Demographic pathways linking sex-chromosome system to adult sex ratio variation across tetrapods. https://doi.org/10.1101/2024.11.17.624031

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