Date of Award

Fall 12-2013

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Chair

Jake Schaefer

Committee Chair Department

Biological Sciences

Committee Member 2

Carl Qualls

Committee Member 2 Department

Biological Sciences

Committee Member 3

Nathan Franssen

Abstract

Convergent evolution is the independent evolution of similar characteristics by means of natural selection. Convergence is a well-known phenomenon, but convergence resulting from equivalent environmental gradients has only been pursued in a few cases. The main purpose of this study was to look for evidence of convergence of life history traits between two sympatrically distributed topminnows. The two species typically separate along a stream size gradient with Fundulus notatus inhabiting the downstream environment, and F. olivaceus inhabiting the upstream headwater environment. However, there are at least three known drainages where the normal distribution pattern is reversed, and F. notatus is found upstream of F. olivaceus. Divergent life history traits are displayed in drainages with the normal distribution pattern, leading to the prediction that life history traits of headwater F. notatus (reversed distribution) will converge on those of headwater F. olivaceus (normal distribution). A field study and an energetics experiment were used to look for convergent life history traits. These data reveal convergent life history traits of headwater F. notatus on downstream F. olivaceus.

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