Ultraviolet signaling in a butterfly is preferred by females and conveys male genetic quality.

Abstract

Indicator models of sexual selection posit that females chose males on the basis of traits that reveal male genetic quality and thereby enjoy increased offspring production. Here we report that females of the butterfly Eurema hecabe receive indirect benefits from choosing males based on their UV wing coloration, a heritable and condition-dependent trait in this species. We first used a large laboratory-bred pedigree to demonstrate a per-family association between inbreeding and male UV trait value. Females exerted choice for UV-bright males within this protocol, and average male UV trait value increased over six consecutive generations presumably due to such selection and despite an increasing rate of pedigree-wide inbreeding. We then experimentally imposed a standard strength of inbreeding upon lines of divergent male UV trait value. Inbreeding depressed the siring performance of low-UV treatment males more severely and resulted in a marginal reduction of their UV brightness, which rebounded sharply following subsequent outcrossing. These findings are consistent with the ornament-based signaling of genetic quality as a function of underlying individual-level mutational load.