Conservation genetics of a desert fish species: the Lahontan tui chub (Siphateles bicolor ssp.)

Abstract

Analysis of the genetic diversity and structure of declining populations is critical as species and populations are increasingly fragmented globally. In the Great Basin Desert in particular, climate change, habitat alteration, and fragmentation threaten aquatic habitats and their endemic species. Tui chubs, including the Lahontan tui chub and Dixie Valley tui chub, (Siphateles bicolor ssp.) are native to the Walker, Carson, Truckee and Humboldt River drainages in the Great Basin Desert. Two populations, Walker Lake and Dixie Valley, are under threat from habitat alteration, increased salinity, small population sizes, and nonnative species. We used nine microsatellite markers to investigate the population genetic structure and diversity of these and nine other tui chub populations to provide information to managers for the conservation of both Walker Lake and Dixie Valley tui chubs. Genetic population structure reflects both historical and contemporary factors, such as connection with Pleistocene Lake Lahontan in addition to more recent habitat fragmentation. Dixie Valley was the most highly differentiated population (pairwise F ST = 0.098−0.217, p < 0.001), showed evidence of a past bottleneck, and had the lowest observed heterozygosity (Ho = 0.607). Walker Lake was not substantially differentiated from other Lahontan tui chub populations, including those located in different watersheds (pairwise F ST = 0.031−0.103, p < 0.001), and had the highest overall observed heterozygosity (Ho = 0.833). We recommend that managers continue to manage and monitor Dixie Valley as a distinct Management Unit, while continuing to maximize habitat size and quality to preserve overall genetic diversity, evolutionary potential, and ecological processes.