Veiled preferences and cryptic female choice could underlie the origin of novel sexual traits

Abstract

Males in many species have elaborated sexual traits that females strongly prefer, and these traits often conspicuously differ among species. How novel preferences and traits originate, however, is a challenging evolutionary problem because the initial appearance of only the female preference or only the male trait should reduce the ability to find a suitable mate, which could reduce fitness for individuals possessing those novel alleles. Here, we present a hypothesis for how novel preferences, as well as the novel male traits that females prefer, can originate, be favoured and spread in polyandrous species. Novel preference mutations can arise as 'veiled preferences' that are not expressed when the corresponding male trait is not present in the population, allowing preferences to be hidden from selection, and thus persist. In those cases when a male trait is present, veiled preferences provide a selective advantage, and females disproportionately produce offspring from preferred males through either mate choice or cryptic female choice. This tips the fitness advantage for novel males, allowing both preference and trait to spread, and limiting selection against them in the absence of the corresponding trait or preference.

Keywords: cryptic female choice; novel female mate preference; novel male mating trait; sexual selection.

Figure 1.

Illustrative example of how veiled preferences can persist in a population, and later lead to selection for novel male traits. When females mate multiply, cryptic choice favours sperm from orange mates (right side of figure), leading to a disproportionate frequency of orange alleles in offspring. This does not occur when mating with multiple non-preferred mates (left). (Online version in colour.)