Sexual selection and condition‐dependence

TLDR

The handicap theory posits that females favor mates with extravagant ornaments that signal quality, and it is commonly assumed that such traits become increasingly condition‑dependent as they are exaggerated. The study questions the extent to which sexual signals reflect sexual selection versus pre‑existing condition‑dependence. The authors find that trait exaggeration does not always increase condition‑dependence; depending on the cost–size relationship, it can become more, less, or unchanged.

Abstract

Abstract The handicap theory of sexual selection suggests that females prefer mates who display extravagant ornaments that advertise their quality or condition. It is often assumed that as such ornamental traits undergo sexually‐selected exaggeration, they must inevitably become more sensitive to condition, and thus more informative. Here, we show that this is not necessarily the case. Depending on the precise form of the relationship between trait size and cost, expression may become more or less condition‐dependent as the trait undergoes exaggeration, or may remain unchanged. This leads us to question how much of the information content of sexual signals can be attributed to sexual selection, and how much to pre‐existing, naturally‐selected condition‐dependence.