Abandoned in the Mojave Desert: revised history of oviparous goodeids (Empetrichthyinae)

Authors: Sonia Hernandez, Christopher Hoagstrom, Wilfredo Matamoros

Year: 2023

Abstract

Empetrichthyinae (poolfishes) is a subfamily endemic to the Mojave Desert, including Crenichthys and Empetrichthys. The biogeography of this group is enigmatic. Throughout most of the 20th Century, researchers debated its phylogenetic affiliation. In 1981, Parenti determined, using skeletal features, that the group belonged to Goodeidae (Cyprinodontiformes) and this finding later gained molecular support. However, this revealed a large geographical gap between Empetrichthyinae and its sister subfamily Goodeinae, which inhabits the Trans-Mexican Volcanic Belt. Hypotheses proposed to explain this disjunction included climate change (desertification), tectonic transport along the Pacific Coast, and immigration from the Great Basin into the Trans-Mexican Volcanic Belt, but no hypothesis was developed in detail. Our study of North American Cyprinodontiformes indicates families within this order diversified among drainages of the Gulf of Mexico. Goodeidae evidently separated from other Cyprinodontiformes via a marine-freshwater transition, likely into a Madrean River drainage that existed at the estimated time of origin (Middle Eocene-Early Oligocene), extending northwest from the western Gulf, along the front of the Sierra Madre Oriental, across southwestern North America. Late Eocene transfer of Madrean tributaries to what became the Oligocene Rio Grande provides a feasible route to the Great Basin, compatible with the estimated time of origin for Goodeidae. Subsequent divergence of Empetrichthyinae corresponds in time with breakup of this drainage, while also accounting for access of Goodeinae to the Trans-Mexican Volcanic Belt. Thereafter, volcanism and uplift of the Sierra Madre Occidental, desertification, river-drainage reorganization with faunal invasions, climatic cooling, and possibly (more recently) human settlement may have all contributed to creating the modern distributional gap between subfamilies.