The effect of developmental temperature and inbreeding on sexual and reproductive traits of female guppies.

Global temperatures are rising and inbreeding is increasingly common in wild populations as habitats become fragmented and population sizes shrink. There is extensive research on how inbreeding or elevated temperatures affect animal performance, but little is known about how these 2 factors interact to affect sexually selected behavior and reproductive traits. We ran a 2 × 2 experiment to investigate how developmental temperature (26 °C or 30 °C) and inbreeding (outbreeding or full-sibling mating) affect female guppies (Poecilia reticulata). We reciprocally cross-bred full-siblings to create inbred and outbred females and measured their sexual attractiveness (via male mate choice tests), fecundity, egg diameter and total egg mass (N = 120 females). Female attractiveness was affected by an interaction between breeding status and temperature. For females reared at 26 °C, males preferred outbred females over inbred females and over both inbred and outbred females raised at 30 °C. In contrast, for females reared at 30 °C, males did not prefer outbred females. Inbreeding and elevated developmental temperature independently reduced egg diameter, indicating that both factors reduce offspring provisioning. Neither inbreeding nor developmental temperature affected fecundity or total egg mass. However, larger and older females produced more eggs, and larger females had heavier clutches. Our results suggest that the fitness effect of inbreeding for females depends on developmental temperature. Climate warming may intensify these genotype-environment interactions thereby increasing the costs of inbreeding. The efficacy of sexual selection in removing deleterious recessive alleles could be reduced if males are less likely to avoid inbred females as temperatures rise.