Morphological variation, genetic structuring, and stable isotopic signatures in the Utah Lake, Utah sucker complex

Authors: David D. Cole, Brian L. Cardall, Karen E. Mock, Todd A. Crowl

Year: 2008 (xl)

Abstract

Population decline in the federally endangered June sucker, Chasmistes liorus, a lakesucker unique to Utah Lake, Utah, has been attributed in part to hybridization with the more widespread Utah sucker, Catostomus ardens. Meristic and morphological ambiguities, presumably the result of hybridization, create a continuum of intermediate forms between Chasmistes and Catostomus extremes and prevent definitive identification to species. Here we describe and evaluate the morphological and genetic variation in suckers in Utah Lake by comparing a morphological analysis with amplified fragment length polymorphism (AFLP) and microsatellite analyses; additionally, we use stable isotopes (¹³C and ¹⁵N ) to compare sucker diet along the morphological gradient. Suckers were differentiated using mouth characters associated with different presumed feeding strategies: planktivory (June sucker) and benthivory (Utah sucker). Although we found no genetic evidence for a deep divergence between June and Utah morphs, slight, but significant, population structuring accompanied the substantial morphological variation. Bayesian model-based genetic clustering detected two sucker populations in Utah Lake, though these clusters were only weakly concordant with morphological groupings or between marker systems. Stable isotopic signatures were congruent with the presumed feeding strategies. The suckers in Utah Lake present an interesting dilemma regarding conservation: should one conserve (breed and stock) a subset of the morphotypic variation in the Utah Lake sucker complex, focusing on the endangered June sucker morphotype, or should one conserve both June sucker and Utah sucker morphotypes in this complex, possibly maximizing evolutionary potential?