Title

Gene flow and migration in populations of Fundulus heteroclitus macrolepidotus located in southeastern Connecticut

Date of Completion

January 1999

Keywords

Biology, Genetics|Agriculture, Fisheries and Aquaculture

Degree

Ph.D.

Abstract

A novel high-throughput method of detecting and analyzing fluorescently tagged RAPDs with the Perkin-Elmer 310 capillary electrophoresis unit was developed. Optimal resolution and sensitivity ranges for data extraction from this system were empirically determined, and found to be in close agreement with experimental results obtained by others. The high throughput methodology was utilized to identify genomic DNA polymorphisms in Fundulus heteroclitus , and quantitate the amount of gene flow occurring between populations. Subpopulations were sampled within two main populations located at Barn Island Marsh in Stonington, Connecticut, and on either bank of the Connecticut River in Old Lyme and Old Saybrook, Connecticut. The Barn Island subpopulations were sampled over two consecutive years. Fischer's exact test revealed the populations were genetically distinct, although the genetic distance separating them was low. Calculations of Weir and Cockerham's Theta P and theta S revealed that the majority of the variation occurred between subpopulations, with relatively little evident between populations. Nem was calculated from the theta values, resulting in values of ranging from 2.0 to 9.0. In all cases, Nem was greater than one, indicating sufficient gene flow to prevent differentiation by genetic drift. Little evidence of temporal stability was found, as the differentiation between populations sampled from Barn Island over two consecutive years was only slightly less divergent than comparison of either to the CT River populations. Detailed analysis of the CT River populations indicated that tidal flow had little, if any effect on gene flow. This pattern of high subpopulation divergence despite low overall difference between populations may indicate high seasonal mortality followed by extensive seasonal redistribution of the surviving genotypes. This effect, which we have termed “functional panmixia” has been recorded in container breeding mosquitoes. ^