Riverscape Genetics: A Management Tool for Long-Lived Colorado River Fishes

Authors: Michael E. Douglas, Marlis R. Douglas, Matthew W. Hopken

Year: 2010 (xlii)

Abstract

Ecological and evolutionary success of widespread, long-lived big river fishes within the intermountain West of North America is best reflected by their ‘riverscape’ genetics. This approach can be a management tool with which to gauge anthropogenic impacts at the ecosystem level. Here, the Bluehead Sucker (Catostomus discobolus; Catostomidae) can be a model organism for adaptive management in this geographically large watershed. Although distributed broadly across the Colorado and Bonneville/ Snake river basins, the Bluehead has experienced rapid, range-wide declines and is now a federal and state ‘species of concern.’ We genetically evaluated 1,100 individuals from 39 locations and examined the deep history of this species by sequencing two fast-evolving mitochondrial DNA genes. Three ESUs (Evolutionarily Significant Units) were identified: the Bonneville Basin/Upper Snake River, the Colorado River Basin, and the lower basin Little Colorado River. We also analyzed 16 microsatellite DNA loci in an attempt to identify basin-wide contemporary evolution. Here, 11 MUs (management units) were identified: One was consistent with the Bonneville Basin/Upper Snake River ESU while 5 were located within the Upper Colorado River basin (1 was the broadly admixed mainstem with 4 others in isolated tributaries). Three MUs were identified in the Lower Colorado River Basin: 2 with tributaries and one comprising all of Grand Canyon. Genetic diversity in Bluehead is maintained by gene flow that is concomitantly eroded within smaller, more isolated populations. A prerequisite for long-term success of this (and other) basin-wide species is metapopulation connectivity, achieved by linking more permanent ‘sources’ with ephemeral ‘sinks’ by way of tractable riverine corridors. Molecular techniques can uniquely gauge these ecological aspects and simultaneously benchmark their diminution via anthropogenic water diversions and willful introduction/ maintenance of invasive (and predatory) fishes.