Riverscape genetics of Roundtail chub in the Upper Colorado Basin

Authors: Marlis R. Douglas, Tyler K. Chafin, Michael E. Douglas

Year: 2013 (xlv)

Abstract

The native big-river fish community in the Upper Colorado River basin is comprised of minnows (Cyprinidae) and suckers (Catostomidae). Both are represented by but a few species, most of which are endemic and either threatened, endangered or considered of conservation concern. Roundtail Chub, Gila robusta is a focal species of the Multi-State Three-Species Conservation Agreement and its propagation and/ or translocation is a potential tool for adaptive management. Such conservation actions should rely on genetic information as a baseline, so as to avoid the potential for outbreeding depression that can result from the intermingling of distinct lineages. In this regard, how genetically distinct are Roundtail Chub populations from the mainstem Colorado River versus those from tributaries? The two habitats differ markedly with regard to flow regimes and community composition, and selective pressures in deep history may have varied considerably among areas. Admixing different local populations may break apart co-adapted gene complexes and reduce fitness in future generations - an outcome that would complicate recovery efforts. To consider this possibility, we evaluated genetic relationships of 450 Roundtail Chub collected from mainstem and tributaries in Wyoming (N=150), Colorado (N=110), and Utah (N=190). We analyzed sequence variation across 2 mitochondrial DNA genes (842 base pairs) as a means of identifying genetic relationships reflecting deep history and relating these patterns with geomorphic features. Second, we examined genetic diversity across fast-evolving microsatellite loci to test for contemporary connectivity and demographic independence among local populations. While small sample sizes from some sites limited statistical power, overall results suggest that management actions should strive to preserve local adaptations among populations and rely upon a drainage-specific focus for adaptive management.