Spatial and temporal variation in genetic composition of larval drift of catostomid suckers

Authors: Michael R. Schwemm, Evan W. Carson, Kevin G. Thompson, Megan J. Osborne, Thomas F. Turner

Year: 2016 (xlviii)

Abstract

Interspecific hybridization is common in catostomid suckers and can present a challenge to management when native and non - native species co-occur. In the Gunnison River basin of western Colorado, native bluehead and flannelmouth suckers interbreed not only with each other but also with introduced longnose and white suckers. Although occurrence of adult hybrids is well documented in this system, little is known about representation of hybrids among larvae. We used species -specific microsatellite markers (N = 4-6) to survey spatial (between streams) and temporal (within streams) variation in the genetic contribution of native and non-native catostomid suckers to larval drift in Cottonwood and Potter creeks, two geographically proximate tributaries to the Gunnison River. Representation of native, non-native, and hybrid sucker larvae differed significantly within and between streams in 2014 and in 2015. In 2014, larvae sampled in Cottonwood Creek (n = 79) were dominated by non-native white sucker (43%), native flannelmouth sucker (13%), and their hybrids (41%). Samples from Potter Creek (n = 157), in contrast, were mostly bluehead sucker (54%), flannelmouth sucker (32%), and their hybrids (14%). In 2015, bluehead sucker represented 100% of larva e sampled in Potter Creek (n =84) and 76% of samples from Cottonwood Creek (n =124). Remaining larvae from Cottonwood in 2015 included near-equal proportions of native flannelmouth sucker (6%), non-native white sucker (10%), and hybrids (8%), with most hybrids represented by advanced backcrosses between bluehead and white suckers (in the direction of bluehead sucker). Implications for management are discussed.