North America’s Desert Fishes: Origins, Diversity, and Conservation.

Authors: Michael Tobler, Casey Ernest

Year: 2025

Abstract

Research on North America’s desert fishes spans more than a century, from studies of their ecology in extreme aridland environments to investigations of their evolutionary origins and the mounting challenges to their persistence under human pressures. Yet, few quantitative syntheses have examined their history, diversity, and conservation. We compiled occurrence records for North American freshwater fishes and intersected them with the boundaries of the Baja California, Great Basin, Mojave, Sonoran, and Chihuahuan deserts. Integrating these data with phylogenetic relationships and conservation assessments, we: (1) generated an inventory of desert fish species and compared taxonomic composition among regions; (2) analyzed colonization, speciation, and extinction dynamics using phylogenetic comparative approaches; (3) identified levels of endemism and biodiversity hotspots across the regions; and (4) summarized conservation status, threats, and urgent needs. Our synthesis revealed a bimodal pattern of desert occupancy, with 118 species from 12 families primarily inhabiting desert habitats. Most belong to Leuciscidae, Cyprinodontidae, and Poeciliidae. Phylogenetic comparative analyses indicated that desert species are more clumped than expected under Brownian motion, with a median transition from non-desert to desert lineages occurring ~15 million years ago. Hidden-state speciation and extinction models further showed elevated net diversification rates in desert fishes, driven by increased speciation and extinction. Spatial analyses highlighted hotspots in the Cuatro Ciénegas valley, portions of the Conchos basin, and tributaries of the lower Rio Grande. More than half of desert fishes are threatened or endangered—disproportionately higher than for non-desert taxa—primarily due to water extraction, non-native species, agricultural and urban pollution, and intensifying drought. Together, these findings underscore both the evolutionary distinctiveness and precarious conservation status of desert fishes across North America.