Morphological and genetic structuring in the Utah Lake sucker complex

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). As a group, suckers in Utah Lake exhibit considerable external morphological variation. 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 and microsatellite analyses. Suckers were morphologically differentiated using mouth characters associated with different feeding strategies: planktivory (June sucker) and benthivory (Utah sucker). Although we found no genetic evidence for a deep divergence between June and Utah morphs, significant, but slight population structuring accompanied the substantial morphological variation. Bayesian model-based genetic clustering analyses detected two sucker populations in Utah Lake; however, these clusters were not strongly concordant with morphological groupings or between marker systems. 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? We explore this question in the context of current genetic and morphological variation in the Utah Lake sucker complex as well as historical information on this complex and other lakesuckers.

Residence time and drift patterns of larval June sucker Chasmistes liorus in the lower Provo River as determined by otolith microstructure

“…Identification of larval Catostomidae was verified by an experienced independent researcher at the larval fish laboratory in the Colorado State University. Chasmistes liorus and C. ardens are morphologically distinct as adults but show only shallow divergence based on molecular genetic evidence (Cole et al , 2008). In addition, there are many individuals with intermediate morphological characters in the Utah Lake Catostomid population.…”

Building a Better June Sucker: Characterization of Mouth Shape in the Captive Brood Stock

“…Second, a study on heritability of mouth morphology that included June sucker, Utah sucker, and hybrids found no difference in survival or growth of young-of-year fish between more pure June sucker, Utah sucker, and hybrids in Utah Lake [13]. Third, in the lake, hybrids are more common than either typical June sucker or typical Utah sucker even if we discount the fish that have been stocked from the captive breeding program [6].…”

“…June sucker are characterized by a wide mouth, thin and widely separated lower lip lobes, and few papillae on the lower lips, whereas, Utah sucker have smaller mouths, broad lower lip lobes that have no gap between them, and highly papillose lip lobes [1,6]. Hybridization is known to occur between the two species and loss of distinct June sucker morphology is considered a significant threat to June sucker [3].…”

Considerations for the Propagation and Conservation of Endangered Lake Suckers of the Western United States

“…Hybridization with Utah Sucker is well documented, such that Miller and Smith (1981) declared that a pure strain no longer exists and that all remaining individuals are of mixed descent. More recent research (Cole et al 2008) indicates that genetic exchange is an ancestral phenomenon, and until future research findings document otherwise, June Sucker used for propagation are targeted based on morphological differentiation in accordance with federal policy (UDWR 2004).…”

“…Therefore, continuous genetic monitoring is important to conservation propagation (Koike et al 2008;Dowling et al 2012). Complicated evolutionary dynamics and systematic challenges inhibit our ability to effectively address many genetic risks of artificially propagating catostomids (Cook 2001;Cole et al 2008). Moreover, contention exists among researchers regarding the efficacy of conserving species complexes and the role of hybridization in recovery (Dowling and Secor 1997;Fiumera et al 2004).…”