Introgression Between Lahontan and Endangered Owens Tui Uhubs,and Apparent Discovery of a New Tui Chub in the Owens Valley,California

Owens tui chubs (Siphateles bicolor snyderi Miller]) have become extirpated throughout most of their range by introgression with introduced Lahontan tui chubs. The remaining non-introgressed Owens tui chub populations persist in a small number of fragmented habitats. These survivors are listed as “endangered” under both the state and federal endangered species acts. This study employs six microsatellite DNA loci to assess degrees of genetic difference within and among populations of Owens and Lahontan tui chubs and their putative hybrids. It reveals four distinct groups of tui chubs: Owens, Lahontan, hybrid Owens × Lahontan, and Cabin Bar. Patterns of microsatellite DNA variation confirm that tui chubs in the Owens River and its tributaries, and Mono Lake tributaries comprise a hybrid swarm. The overall degree of introgression between Lahontan and Owens tui chubs is approximately 40%, while the remaining 60% derives from Owens tui chub’s original genetic composition. Unexpectedly, Owens tui chubs are more genetically similar to Lahontan tui chubs than to Cabin Bar tui chubs, although they share the same river basin with the latter. Cabin Bar tui chubs possess a 3 bp deletion in the flanking region of microsatellite locus Gbi-G79. We give the Cabin Bar tui chub a common name “toikona tui chub” to distinguish it from the Owens tui chub, and recommend independent protection and recovery efforts. Management practices should prevent any future genetic mixing of non-introgressed Owens, toikona, or Lahontan tui chubs with each other, or with the hybrid swarm. Habitats of Owens and toikona tui chubs should remain isolated from the Owens River. Toikona tui chubs should be established in multiple sites.