Disentangling the drivers of diversification in an imperiled group of freshwater fishes (Cyprinodontiformes: Goodeidae)

Background: One of the most perplexing questions in evolutionary biology is why some lineages diversify into many species, and others do not. In many cases, ecological opportunity has played an important role, leading to diversification along trophic or habitat-based axes. The Goodeidae (Teleostomi: Cyprinodontiformes) are a family of freshwater fishes with two subfamilies: Goodeinae (42 species, viviparous, heterogeneous habitats, Mesa Central of Mexico) and Empetrichthyinae (4 species, oviparous, homogeneous habitats, Great Basin of the United States). These discrepant sets of characteristics and their sister-group relationship make the goodeids amenable to a comparative study of diversification. We gathered lateral body images from more than 1,600 specimens of all extant species in the family. Geometric morphometric, and phylogenetic comparative analyses were used to address whether higher species diversity correlates with higher rates of morphological shape evolution and whether
th...