The correlation between anisogamy and sexual selection intensity—the broad theoretical predictions

Abstract

Abstract Darwin and Bateman suggested that precopulatory sexual selection is more intense on males than females, and that this difference is due to anisogamy (i.e., dimorphism in gamete size and number). While a recent paper apparently presents empirical support for this hypothesis, another appears at first sight to present evidence against it. We argue that this is partly due to lack of transparent theoretical predictions, and discuss and analyze sexual selection theory in relation to anisogamy evolution. On one hand, we find that there exists relatively little theory that can directly address all the tested predictions; on the other, the picture painted by current theory indicates that both sets of empirical results broadly match predictions about the causal link between anisogamy and sexual selection, thus reconciling the two apparently opposing claims. We also discuss in a very broad, general sense how anisogamy is expected to affect sexual selection.