Date of Award

Summer 8-1-2015

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Biological Sciences

Committee Chair

Jake Schaefer

Committee Chair Department

Biological Sciences

Committee Member 2

Brian Kreiser

Committee Member 2 Department

Biological Sciences

Committee Member 3

Carl Qualls

Committee Member 3 Department

Biological Sciences


Temperature is one of the most pervasive and influential abiotic factors affecting the life histories of fish, regulating a host of physiological processes and influencing behavioral thermoregulation. Fundulus notatus, the blackstripe topminnow, and F. olivaceus, the blackspotted topminnow, are widely distributed species located in drainages along the northern part of Gulf of Mexico (30°N latitude) and as far north as southern Illinois (39°N latitude). However, F. notatus has a much broader range reaching up into the Great Lakes (43°N latitude). Due to their broad geographical range, these populations inhabit a wide range of thermal regimes, thus having to locally adapt to their surrounding thermal environments. Variable temperature regimes along latitudinal gradients might be responsible for adaptive differences in thermal biologies among populations. I examined whether latitude reflects intra- and interspecific differences in thermal preference and tolerance across a gradient of temperatures. Fundulus notatus were collected at four latitudes (southern Mississippi – 30°N, northern Alabama – 34ºN, southern Illinois - 38°N, and northern Ohio - 41°N). Fundulus olivaceus were collected at three latitudes (southern Mississippi – 31°N, northern Alabama – 34°N and central Missouri – 37°N). These two species are known to hybridize throughout their sympatric distribution. Thus, I quantified hybridization under different thermal shifts in the Pearl and Sabine River drainages to examine the influence of temperature on hybridization between sympatric populations. Understanding the influence of temperature within and among species may allow us to gain further knowledge into the nature of variation of thermal adaptation.