Thesis Title

Nymphophiline Phylogenetic Relationships Based On Mitochondrial DNA Sequences

Author

Kayla Clift

Date of Graduation

Summer 2003

Degree

Master of Science in Biology

Department

Biology

Committee Chair

John Heywood

Subject Categories

Biology

Abstract

Springsnails (Hydrobiidae: Nymphophilinae) are diverse, obligate to water, highly endemic, and do not appear to be subject to introgression. These features make them excellent subjects for evolutionary and biogeographical study, however an absence of robust phylogenetic hypotheses has limited their use. Morphology-based phylogenetic studies of hydrobiids resulted in poorly resolved relationships and indicated that most characters used are homoplasic. Molecular data are useful for addressing unclear phylogenetic relationships that are hard to discern using traditional methods. Sequences of mitochondrial DNA evolve rapidly are appropriate for inferring phylogenetic relationships among closely related species. Currently only cytochrome c oxidase subunit I (COI) primers are used consistently for the study of hydrobiids. In this study, amplification primers were designed to target a portion of mitochondrial NADH dehydrogenase subunit I (NDI) for hydrobiid snails. NDI genes from 33 specimens comprising 28 nymphophiline species were sequenced to determine the phylogenetic relationships among species with disjunct distributions in the eastern and western United States. For 25 of these species, available COI sequences were also uses to infer phylogenetic realtionships. NDI, COI, and combined phylogenies indicate that eastern taxa are clearly differentiated from western taxa. Chi-square analysis of pairwise genetic distances found NDI to be evolving significantly faster than COI. The region between the mitochondrial 16S ribosomal RNA(16S) gene and NDI was sequenced for Marstonia agarhecta and found to include genes that code for tRNA leucine(UUR) and tRNA leucine(CUN). The gene order in this region is identical to that in the prosobranch Littorina saxatilis, but differs from that of the prosobranch Plicopurpura columellaris by a tRNA translocation. This translocation is presumably limited to Mesogastropoda or some part of this group.

Copyright

© Kayla Clift

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