Evolutionary Relationships of the Fish Lake Valley Tui Chub

Matthew A. Campbell, Serra C. Perry, Khyana N. Yearwood, Grace Auringer, Nick Buckmaster, Amanda J. Finger

The Great Basin of western North America is a vast, dry region with scattered rivers, springs, and lakes that have given rise to unique fish species over millions of years. Among these are the Tui Chubs, a group of minnows in the genus Siphateles. For decades, most of the diversity in these fishes was lumped together under one name, Siphateles bicolor. As a result, many distinctive and isolated populations have had uncertain conservation status.

One such population is the Fish Lake Valley Tui Chub (FLVTC) from southwestern Nevada, the only native fish in that valley. To clarify its identity, we analyzed both mitochondrial DNA and thousands of genome-wide genetic markers from Tui Chubs across the Great Basin. The Fish Lake Valley Tui Chub was found to be the earliest-branching and highly distinct lineage of S. obesus, supporting its recognition as a separate subspecies. Geologic evidence aligns with this result: Fish Lake Valley was once connected to the larger Lahontan Basin about two million years ago, allowing gene flow until roughly half a million years ago, when isolation set the stage for distinct evolution.

This study also uncovered an even deeper split. Fishes in Oregon’s Alvord Basin, long classified within Siphateles, are genetically and anatomically different enough to deserve their own genus. The authors propose a new name, Epizon, meaning “survivor,” to highlight their persistence in harsh desert conditions. Two species, Epizon alvordensis and Epizon boraxobius, are now formally placed in this new genus.

These findings refine our understanding of fish diversity in the Great Basin and highlight how much remains hidden in isolated desert waters. Recognizing species and subspecies matters for conservation: without clear taxonomy, unique lineages may be overlooked in management decisions. The Fish Lake Valley Tui Chub, for example, is confined to a small area and is genetically unique, making it a conservation priority. More broadly, this study shows that freshwater fishes of the Great Basin—though few in number compared to other regions—represent an important piece of North America’s evolutionary and biodiversity heritage.

Status: This work is published in Zookeys 9/2025