The determinants of genetic diversity in butterflies

Alexander Mackintosh,Dominik R Laetsch,Martin Waterfall,Roger Vila,Konrad Lohse,Alexander Hayward,Brian Charlesworth

doi:10.1038/s41467-019-11308-4

Alexander Mackintosh, Dominik R Laetsch + Show 5 more

Open Access

https://doi.org/10.1038/s41467-019-11308-4

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Abstract

Under the neutral theory, genetic diversity is expected to increase with population size. While comparative analyses have consistently failed to find strong relationships between census population size and genetic diversity, a recent study across animals identified a strong correlation between propagule size and genetic diversity, suggesting that r-strategists that produce many small offspring, have greater long-term population sizes. Here we compare genome-wide genetic diversity across 38 species of European butterflies (Papilionoidea), a group that shows little variation in reproductive strategy. We show that genetic diversity across butterflies varies over an order of magnitude and that this variation cannot be explained by differences in current abundance, propagule size, host or geographic range. Instead, neutral genetic diversity is negatively correlated with body size and positively with the length of the genetic map. This suggests that genetic diversity is determined both by differences in long-term population size and the effect of selection on linked sites.

Highlights

Under the neutral theory, genetic diversity is expected to increase with population size
We show that neutral genetic diversity in European butterflies varies over an order of magnitude, and that this variation is neither significantly correlated with current abundance nor key life-history traits
We do not find any significant relationship between propagule size or longevity and neutral genetic diversity

Summary

Introduction

Genetic diversity is expected to increase with population size. We show that genetic diversity across butterflies varies over an order of magnitude and that this variation cannot be explained by differences in current abundance, propagule size, host or geographic range. Neutral genetic diversity is negatively correlated with body size and positively with the length of the genetic map This suggests that genetic diversity is determined both by differences in long-term population size and the effect of selection on linked sites. Because the efficacy of selection depends on the product Nes, selection is expected to be more efficient and remove more neutral linked sites in species with large Ne. Recently, Corbett-Detig et al.[16] have shown that the proportional reduction of neutral diversity due to selection at linked sites does correlate with measures of census size such as geographic range and (negatively) with body size. While CorbettDetig et al.[16] argue that this can explain “... why neutral diversity does not scale as expected with census size”, a reanalysis of their data[17] concluded that the effect of selection on linked neutral diversity is too small to provide a general explanation for the narrow range of genetic diversity seen in nature

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