Under the neutral theory, genetic diversity is expected to be an increasing function ofpopulation size. However, comparative studies have consistently failed to find strong correlations between measures of census population size and genetic diversity. Instead, a recent comparative study across several animal phyla identified propagule size as the strongest predictor of genetic diversity, suggesting that r-strategists that produce many offspring but invest little in each, have greater long-term effective population sizes.However, this cannot explain differences in genetic diversity across taxa that show little or no variation in reproductive strategy. We present a comparison of genome-wide levels of genetic diversity across 38 species of European butterflies (Papilionoidea). 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 plant use 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 neutral sites.
- evolutionary genetics
- genetic variation