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Dryad

Genetic variation in sexual size dimorphism is associated with variation in sex-specific plasticity in Drosophila

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Mar 27, 2023 version files 723.76 KB
Mar 31, 2023 version files 20.97 MB

Abstract

The difference in body size between females and males, or sexual size dimorphism (SSD), is ubiquitous, and yet we have a poor understanding of the developmental-genetic mechanisms that generate it, and how these mechanisms may vary within and among species. Such an understanding of the genetic architecture of SSD is important if we are to evaluate alternative models of SSD evolution, but is difficult to describe because SSD is a characteristic of populations, not individuals. Here, we overcome this challenge by using isogenic lineages of Drosophila to measure SSD for 196 genotypes. We demonstrate extensive genetic variation for SSD, primarily driven by higher levels of genetic variation for body size among females than males. While we observe a general increase in SSD with sex-averaged body size (pooling for sex) among lineages, the vast majority of variation in SSD is independent of sex-averaged body size, and shows a strong genetic correlation with sex-specific plasticity, such that increased female-biased SSD is associated with increased body-size plasticity in females. Our data are consistent with the condition-dependence hypothesis of sexual dimorphism, and suggest that SSD in Drosophila is a consequence of selection on the developmental-genetic mechanisms that regulate the plasticity of body size.