Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

David W. Foltz

Abstract

Genetic and morphological variation were studied in a brooding (ovoviviparous) and morphologically variable freshwater snail (Viviparus georgianus (Lea)) in the southeastern United States. Eleven populations were clustered into three genetically isolated, allopatric species characterized by 7 to 15 diagnostic loci out of the 38 loci examined. These allopatric species were an eastern species (in eastern and southern Florida), a western species (in the Florida panhandle), and a central species in the Ochlockonee River. Nei's standard genetic distances between species were large (0.23-0.52) compared to within-species distances (0.00-0.06). Moreover, genetic distances between the Ochlockonee River species and other species were larger than the distance between the eastern and western species. Hierarchical F-statistics for differentiation among sites within drainage systems (F$\sb{\rm SD}$) of the western and eastern species were large (0.519 and 0.387, respectively). The F$\sb{\rm DT}$ values (differentiation among drainage systems within the total area sampled) were negative, so most of the intraspecific genetic differentiation was due to differences among populations within drainage systems, rather than to differences among systems. Canonical discriminant analysis of nine shell measurements separated all three species with little overlap. The type specimens of the Viviparus georgianus complex and type locality specimens were compared to the discriminant function and canonical discriminant analyses of shell characters of the studied samples to assign correct species names. The western species and Ochlockonee River species appear to be Viviparus goodrichi Archer and Viviparus limi Pilsbry, respectively, which were originally described as subspecies of Viviparus contectoides (= Viviparus georgianus). The eastern species is Viviparus georgianus (Lea). The three species can be distinguished by the following morphological characteristics: V. goodrichi has a more globose shell with a larger aperture than V. limi; V. georgianus has shorter aperture height than the other species. Also, these three species can be identified reliably using allozyme characters.

Pages

99

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