Inbreeding strategies under social and sexual complexity: insights from female and male guppies

Animals are typically expected to avoid mating with relatives due to the costs associated with incestuous matings. Yet for more than 4 decades, theoretical models have consistently suggested that animals may tolerate, or even prefer, mating with relatives under a broad range of conditions. However, empirical studies that evaluate inbreeding strategy under alternative social and sexual contexts remain scarce. Here, we investigate how experimental variation in sexual and social complexity influence precopulatory inbreeding avoidance behaviors in the guppy <i>Poecilia reticulata</i>, a species known to experience inbreeding depression. In an integrated set of experiments, we examined if sexual and affiliative behaviors of virgin and experienced females and males were differentially directed towards either related or unrelated individuals. In simple social context, neither virgin nor experienced females or males showed a preference for related or unrelated partners. In more sexually and socially complex free-swimming arenas, females appeared to respond slightly more to related males, but this effect was not statistically significant once corrected for multiple comparisons; male preference remained unchanged. Overall, these findings challenge previous reports of preference shifts between virgin and experienced female guppies and suggest that inbreeding avoidance behaviors may be less prevalent in complex social environments than previously thought.