Date of Award:

5-2014

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Watershed Sciences

Committee Chair(s)

Todd Crowl

Committee

Todd Crowl

Committee

Karen Mock

Committee

Phaedra Budy

Committee

Chris Luecke

Committee

Mike Pfrender

Abstract

Natural selection within the sucker family of fishes has produced populations including typical benthic (bottom-feeding) suckers (Catostomus) and lakesuckers (Chasmistes), mid-water plankton eaters, in several large western North American lakes. Suckers of intermediate morphology (shape) exist in a continuum of head, mouth, and body characteristics between these two extremes. All current lakesuckers are listed Endangered, and population declines have been attributed in part to hybridization with their Catostomus neighbors.

Chapter 2 describes the investigation of the relationship between morphology and genetics of June sucker, a lakesucker, and Utah sucker, a benthic sucker, in Utah Lake, Utah. Despite the substantial morphological differences, June sucker and Utah sucker were indistinguishable genetically. Although many suckers were of intermediate morphology, there was no evidence of hybridization between ancient June sucker and Utah sucker lineages, suggesting perhaps the Utah Lake population is diverging into two populations rather than converging into one.

Chapter 3 describes the ecology of Utah Lake suckers. Telemetry studies using surgically implanted transmitters revealed little difference in movement and distribution of June sucker and Utah sucker or in the timing of their spawning runs. An investigation into diet confirmed that June sucker were predominantly planktivorous (plankton eaters) whereas Utah sucker were benthivorous (bottom feeders), with intermediates in between.

Chapter 4 examines morphology, genetics, and diet of the sucker population in Jackson 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 lakesuckers (Snake River sucker?). Similar to the Utah Lake suckers, no genetic evidence was found for deep divergence between lakesucker and Utah (benthic) sucker in Jackson Lake or for hybridization among two ancient lineages. Also as in Utah Lake suckers, an investigation into diet showed that lakesuckers were predominantly planktivorous (plankton eaters) whereas Utah sucker were benthivorous (bottom feeders), with intermediates exploiting both food sources. Morphologically, the lone Snake River sucker specimen was extremely similar to current lakesuckers in Jackson Lake, suggesting that the Snake River sucker is not extinct and in need of a status update.

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