Yseult Héjja-Brichard, Julien P Renoult, Tamra C Mendelson

A preference for mating with conspecifics over heterospecifics is fundamental to the maintenance of species diversity in sexually reproducing organisms. This type of assortative mating is often stronger between closely related sympatric species as compared to allopatric species, resulting from processes such as reinforcement or differential fusion. In animals, this pattern has been demonstrated across the genus Drosophila, however, most empirical evidence for stronger assortative mating in sympatry comes from studies of two or only a few species. To infer general patterns requires broader comparative analyses. We therefore compared mate preferences in sympatric and allopatric species of darters (genus Etheostoma). We performed a meta-analysis of 15 studies, encompassing 21 species. As expected, we found stronger preferences for conspecifics over heterospecifics across studies, species, and sexes. We further found stronger preferences for conspecific mates in sympatric as compared to allopatric species. This was especially true for females, consistent with the idea that mate choice might be more costly for females than males.