Stream hierarchy defines riverscape genetics of a North American desert fish

Authors: Michael E. Douglas, Marlis R. Douglas

Year: 2012 (xliv)

Abstract

Global climate change is apparent within the southwestern deserts of North America, where record drought is reflected within the 640,000 km2 of the Colorado River. To discern the manner by which natural and anthropogenic drivers have compressed fish biodiversity, and to establish a baseline for future climate change effects, the Stream Hierarchy Model (SHM) was employed to juxtapose fluvial topography against molecular diversities of 1,092 Bluehead Sucker [Catostomus (Pantosteus) discobolus]. Microsatellite analyses (16 loci) subdivided the Colorado River Basin into seven management units (MUs). One is an admixed cline of three gene pools within mainstem and lower-gradient tributaries of the mainstem. Six others are distinct not only genetically but demographically (i.e., migrants/ generation <9.7%). Two of these (i.e., Grand Canyon, Canyon de Chelly) are defined by geomorphology, two others (i.e., Fremont-Muddy and San Raphael rivers) are isolated by sharp declivities as they drop precipitously from the west slope into the mainstem Colorado/ Green rivers, another represents an isolated impoundment (i.e., Ringdahl Reservoir WY), while the last corresponds to a recognized subspecies (i.e., Zuni River, NM). The evolutionary potential of endemic fishes (i.e., MUs) are clearly represented in our data, yet their arbiter will be the unrelenting natural and anthropogenic water depletions that will precipitate yet another conservation conflict within this unique but arid region.