Biological Sciences, School of


Date of this Version

December 2006


A DISSERTATION Presented to the Faculty of the Graduate College at the University of Nebraska In partial Fulfillment of Requirements For the Degree of Doctor of Philospophy. Major: Biological Sciences. Under the Supervision of Professor Guillermo Ortí. Lincoln, Nebraska, December, 2006. Copyright 2006 Michael L. Bessert.


The overarching theme of this research was to investigate hierarchical levels of relatedness in natural populations of the cycleptid fishes (blue suckers), a widespread genus in North America that is of conservation concern throughout. Phylogenetic analysis of mitochondrial DNA sequences revealed that the two described Cycleptus species, C. elongatus and C. meridionalis are not reciprocally monophyletic, yet do not share any haplotypes. Although lineage sorting is incomplete, Bayesian coalescent analyses indicate that the two groups diverged early in the Pleistocene and have been reproductively isolated since. Whether they should be synonymized as C.elongatus and recognized as subspecies is open for debate. Due to differing morphological and allozyme profiles, the author is hesitant to call for this revision. Phylogenetic analyses also revealed that cycleptids in the Rio Grande are monophyletic and clearly divergent from the C. meridionalis/C. elongatus clade. Morphology is being revisited in Rio Grande specimens and a species description is underway. A novel suite of genus-specific, diploid microsatellite markers was also developed for population genetic analyses. Due to the tetraploid nature of these fishes, a single primer pair often coamplifies multiple paralogous loci, limiting the usefulness of such markers; thus, a new technique was developed to isolate paralogous loci from one another. Genotypic data from isolated paralogs is consistent with functional diploidy and an allotetraploid origin for the family (Catostomidae). Population genetic analyses revealed significant isolation by distance and reduced allelic richness in the upper Missouri River, which has been fragmented by six dams and reservoirs for 50-60 years. These results are in contrast with those from the comparably-sized, but unimpounded, Mississippi River. These differences are noteworthy because only 5-6 generations have passed since the dams were constructed, rendering this one of the earliest detections of genetic effects of habitat fragmentation. Additional monitoring of this system with repeated genetic surveys is strongly recommended. Finally, rangewide population genetic analyses detected nine distinct subpopulations. Four occur in drainages outside of the Mississippi Basin while five occur within the basin. Whether or not the five intrabasin groups are ecologically exchangeable is unknown. Further study of specific subpopulations is encouraged.
Advisor: Guillermo Ortí

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