Independent effects of familiarity and mating preferences for ornamental traits on mating decisions in guppies

The avoidance of familiar individuals as mates can act to maximize the benefits of polyandry or might help to minimize inbreeding in small or highly philopatric populations. As previous mates are also familiar, the effects of familiarity and mating history can often be confounded. Here, we disentangle these effects on mating decisions in the guppy, Poecilia reticulata, and examine their influence on sexual selection. In 3 experiments, males and females were 1) able to mate, 2) had visual and olfactory contact, or 3) had visual contact only. Familiarity was successfully acquired via visual cues, and females were in all cases more likely to mate with unfamiliar than with familiar males, indicating that familiarity is a more important determinant of mating outcome than mating history. Males did not court unfamiliar females any more than familiar females and did not differentially allocate sperm. Familiarity did not alter the strength of sexual selection on male coloration: we found overall positive selection for bright, large males. Female preferences for unfamiliar males and ornamental traits may therefore be largely independent.