The seemingly transparent wings of many insects have recently been found to display unexpected structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Furthermore, to date investigations of WIPs have not fully considered how they are actually perceived by the viewers' colour vision. Here, we use multispectral digital imaging and a model of Drosophila vision to compare WIPs of male and female Drosophila simulans from replicate populations forced to evolve with or without sexual selection for 68 generations. We show that WIPs modelled in Drosophila vision evolve in response to sexual selection and provide evidence that WIPs correlate with male sexual attractiveness. These findings add a new element to the otherwise well-described Drosophila courtship display and confirm that wing colours evolve through sexual selection.

Intralocus sexual conflict results from sexually antagonistic selection on traits shared by the sexes. This can displace males and females from their respective fitness optima, and negative intersexual correlations (rmf) for fitness are the unequivocal indicator of this evolutionary conflict. It has recently been suggested that intersexual fitness correlations can vary depending on the segregating genetic variation present in a population, and one way to alter genetic variation and test this idea is via inbreeding. Here, we test whether intersexual correlations for fitness vary with inbreeding in Drosophila simulans isolines reared under homogenous conditions. We measured male and female fitness at different times following the establishment of isofemale lines and found that the sign of the association between the two measures varied with time after initial inbreeding. Our results are consistent with suggestions that the type of genetic variation segregating within a population can determine the extent of intralocus sexual conflict and also support the idea that sexually antagonistic alleles segregate for longer in populations than alleles with sexually concordant effects.

Summary1. Variation in the strength of age-dependent natural selection shapes differences in ageing rates across species and populations. Likewise, sexual selection can promote divergent patterns of senescence across the sexes. However, the effects of these processes on the evolution of ageing have largely been considered independently, and interactions between them are poorly understood. 2. We use experimental evolution to investigate how natural and sexual selection affect life span and ageing in Drosophila simulans. 3. Replicate populations were evolved under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and at one of two temperatures, 25°C (relaxed natural selection) or 27°C (enhanced natural selection), in a fully factorial design. We measured longevity in 150 individually housed flies taken from each of three replicate populations per selection regime. 4. We found that natural and sexual selection affected the evolution of life span via sex-specific effects on different ageing parameters (ageing rate vs. baseline mortality): natural selection reduced the rate of ageing in both sexes but increased male baseline mortality, while sexual selection elevated baseline mortality in both sexes but particularly in males. 5. This means that sexual and natural selection interacted to reduce male life span but acted on female life span by independently affecting particular ageing parameters. Sex-specific effects of sexual and natural selection may help explain the diverse patterns of ageing seen in nature but complicate predictions about how ageing and life span evolve across the sexes