Male preference for conspecific females depends on male size in the splendid darter, Etheostoma barrenense

Mating preferences vary among individuals in response to a number of factors, such as the age and phenotype of the choosing individual. However, studies addressing variation in mating preferences generally focus on female preferences and usually are limited to choice within a species. Variation in preferences likely also exists at the species boundary, affecting an individual's propensity to mate with heterospecific individuals. In darters (Percidae: Etheostoma), male mating preferences are thought to prevent interbreeding between species, with male preferences for conspecifics sometimes as strong as, or stronger than, females'. In the current study, we tested whether male size and coloration predicts preference for conspecific females in Etheostoma barrenense. Previous studies have shown that males of this species strongly prefer conspecific females relative to females of the sympatric congener, the banded darter, Etheostoma zonale; however, those studies did not consider whether variation in male size or coloration affected preferences. Comparing large and small males of E. barrenense in dichotomous choice assays, we found that larger males exhibited stronger preferences for conspecific females and had proportionally more red coloration than smaller males. The proportion of red coloration did not significantly predict male preferences, suggesting that male size rather than male coloration predicts variation in male mating preferences for conspecific females in E. barrenense. Male size is often considered an indicator of individual quality. Alternatively, size might better reflect age in the focal species, suggesting that experience and learning may shape male preferences for conspecific females. (c) 2020 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.