Female reproductive mode shapes allometric scaling of male traits in livebearing fishes (family Poeciliidae)

Reproductive mode is predicted to influence the form of sexual selection. The viviparity driven conflict hypothesis posits that a shift from lecithotrophic (yolk-nourished) to matrotrophic (mother-nourished or placental) viviparity drives a shift from pre-copulatory toward post-copulatory sexual selection. In lecithotrophic species, we predict that pre-copulatory sexual selection will manifest as males exhibiting a broad distribution of sizes, and small and large males exhibiting contrasting phenotypes (morphology and coloration); conversely, in matrotrophic species an emphasis on post-copulatory sexual selection will preclude these patterns. We test these predictions by gathering data on male size, morphology, and coloration for five sympatric Costa Rican poeciliid species that differ in reproductive mode (i.e. lecithotrophy vs matrotrophy). We find tentative support for these predictions of the viviparity driven conflict hypothesis, with some interesting caveats and subtleties. In par...