Date of Award

8-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Biological Sciences

Advisor

Adler, Peter H

Committee Member

Knap, Halina

Committee Member

Ptacek, Margaret

Abstract

Cryptic biodiversity, the presence of suborganismal variation in isomorphic populations of organisms, can have implications for management and conservation. Ecological variation in habitat and host species of populations of the black fly Simulium johannseni suggested the potential for cryptic biodiversity. Polytene chromosomes of larvae belonging to the S. johannseni group of black flies were characterized to discover fixed and polymorphic rearrangements. Larvae of S. johannseni from Wisconsin, South Carolina, and Alabama and of the closely related S. parmatum from South Carolina and Florida were analyzed. Simulium johannseni can be divided into two cytoforms corresponding to geographic location. Cytoform A, found in Wisconsin, was selected as the chromosomal standard reference; it has 15 polymorphic inversions. Cytoform B, found in South Carolina and Alabama, has three fixed inversions and three polymorphic inversions. Cytoform B shares one polymorphic inversion with cytoform A; one of the fixed inversions in cytoform B is found as a polymorphism at low frequency in cytoform A. Further study is needed to determine if these two cytoforms represent separate species or extremes in clinal chromosome variation. Simulium parmatum has three fixed inversions and one polymorphic inversion, which is possibly sex-linked. Simulium parmatum shares two fixed inversions with S. johannseni cytoform B and has one unique fixed inversion. The polymorphic inversion in S. parmatum is shared with both cytoforms of S. johannseni, but in S. parmatum it was found only in the heterozygous state in males, suggesting it is Y-linked in S. parmatum. Evolutionary relationships were inferred based on shared inversions. The shared inversions indicate that S. johannseni cytoform B and S. parmatum are more closely related to each other than to S. johannseni cytoform A. Further study of additional populations in the S. johannseni group and an outgroup are needed to test the relationships presented in the current analysis.

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