Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 39-47). Also available on the World Wide Web.

The spatial scales at which ecological phenomena are viewed constrain the results of interactions between species and their environments. In lake ecosystems, important dynamics have been identified at the landscape scale and the macrohabitat scale. To determine if landscape-scale effects and macrohabitat-scale effects are important in survival and growth of young June suckers, we compared variation among sites in Utah Lake. Large semi-permeable cages were used to house June suckers in situ at five sites representing landscape-scale variation and two sites representing macrohabitat-scale variation in Utah Lake. We compared survival and growth among sites and related it to resource availability (zooplankton abundances), temperature, and disturbance regime to determine if these were possible drivers of variation. Provo Bay had the highest mean survival and high survival in all four cages. Growth differed among sites: Provo Bay and the northwest site had the highest and lowest mean growth rates, respectively. Survival was higher in vegetated water than open water, whereas growth was significantly higher in open water. Zooplankton densities were highest in Provo Bay and the open water habitat, suggesting a positive relationship between food abundance and growth. Temperature patterns were not consistent with differences in growth among sites. Disturbance was greater in the open lake, which may partly explain the higher survival rates in Provo Bay.

Ecomorphological specialization within Catostomidae in several large western North American lakes has produced populations including typical benthic suckers (Catostomus) and lakesuckers (Chasmistes), mid-water planktivores, with a continuum of morphologies existing between them. All extant lakesuckers are endangered, and population declines have been attributed in part to hybridization with sympatric Catostomus spp. Chapter 2 describes assessment for concordance of morphological and genetic variation in suckers in Utah Lake, Utah (June sucker, Chasmistes liorus; Utah sucker, Catostomus ardens; and suckers of intermediate morphology) by comparing a morphological analysis with amplified fragment length polymorphism and microsatellite analyses. Suckers were differentiated using characters associated with presumed feeding strategies: zooplanktivory (June sucker) and benthivory (Utah sucker). No molecular evidence was found for deep genetic divergence between morphs or for hybridization among ancient lineages. Slight population structuring accompanied substantial morphological variation. Chapter 3 describes the investigation of distribution and movement, spawning behavior, and diet of suckers in Utah Lake and their growth at different densities in a laboratory experiment. Acoustic / radio telemetry revealed little difference in movement and distribution of June sucker and Utah sucker or in timing of spawning runs. Stable isotopes analysis revealed that Utah sucker were enriched in 13C relative to June sucker as presumed diets would predict. Intermediate morphs were intermediate for δ13C and δ15N. Neither species nor density was a significant predictor of growth rate of June sucker or Utah sucker reared at different conspecific densities. Chapter 4 examines morphology, genetics, and diet of the sucker population inJackson Lake, Wyoming, once home of the extinct Snake River sucker, Chasmistes muriei, a lakesucker known from a single specimen. Currently, suckers in Jackson Lake are identified as Utah sucker; however, recently sampled individuals resemble lakesucker. No molecular evidence was found for deep genetic divergence between lakesucker and benthic morphs or for hybridization among ancient lineages. The benthic morph was significantly enriched in 13C relative to the lakesucker morph, consistent with presumed diets. Morphologically, the lone Snake River sucker holotype specimen grouped strongly with extant lakesucker morphs, suggesting that the status of the Snake River sucker be updated accordingly.

Low copy number anonymous nuclear loci were used to search for species markers in four species of Klamath Basin suckers. We sequenced 28 randomly chosen loci representing 10,421 bp; 21 loci were similar to sequences in GenBank. Eight fixed sequence differences were found among Klamath species. Locus 120 contained rare but diagnostic markers for Deltistes luxatus and for Catostomus rimiculus. Locus 4 also contained three rare but unique sites in Catostomus rimiculus. No sequence differences were found between Chasmistes brevirostris and Catostomus snyderi. Loci 4 and 120 exhibited allele frequency differences between Rogue River C. rimiculus and all Klamath Basin suckers. Genotype BB of locus 4 was a fixed diagnostic marker and genotype BB of locus 120 was a frequency dependent marker for Rogue C. rimiculus. Although Klamath suckers represent three genera, very limited variation was found among 10,431 base pairs. We examined phylogenetic patterns of five loci in eleven catostomid genera and 25 species to determine if the homogeneity in the Upper Klamath Basin was due to massive hybridization and introgression or to retention of ancestral sequences. Two loci with no similarity to GenBank sequences (non-coding loci) and three loci with substantial similarity to GenBank sequences (coding loci) gave similar results, providing support for various subfamilies and tribes, more support for eastern genera and little support for western genera. Each locus was a mosaic of species or population markers, sometimes providing discriminatory power for allopatric populations of a species, such as C. macrocheilus, while not discriminating other species. Upper Klamath Basin species were noteworthy in their lack of autapomorphies, but had similar numbers of derived informative sites as other catostomins. Upper Klamath Basin species consistently shared ancestral or equivocal informative sites either with moxostomatins or a variable group of western species and shared derived sites with other western species, especially C. occidentalis. The data suggest that Upper Klamath Basin species have retained a largely ancestral genome at these loci. Thus, the failure of this technique to uncover significant variation in Upper Klamath Basin species may be a reflection of their plesiomorphic genome at these loci and not necessarily hybridization. / Graduation date: 2004