Electrophoretic and Morphologic Comparisons of Sylvilagus floridanus and S. audubonii in Texas

Abstract

Genetic and morphologic characteristics were analysed and compared for Sylvilagus audubonii and S. floridanus collected from two locations in Texas. The two species are genetically similar (S = 0.884). Mean individual heterozygosity was calculated to be 0.028 and 0.045 for S. floridanus and S. audubonii respectively. Species differences were detected in 11 of 22 morphologic characters. Significant differences in variable means were not reflected in significant size and shape differences among variability profiles. In recent years workers have used multiple data sets combining morphologic, genetic, and behavioral characteristics to understand the taxonomic and ecological relationships of closely related species. Disagreement between morphological and biochemical characteristics can lead to conflicting interpretations of the association between phenetic groups based on morphologic classification and those derived from biochemical data. Relatively little work has been conducted that documents electrophoretic variation and levels of genetic variability within, and congeneric genetic relationships between lagomorph species. Considerable work has been conducted comparing the morphology of Sylvilagus spp. (Hall, 1951) and intraspecific geographic variation in morphology (Diersing, 1981). Little work has been done with lagomorph genetics in conjunction with morphological analyses. This study was conducted to describe the electrophoretic characteristics of S. floridanus and S. audubonii, and to test the congruence of results obtained from electrophoretic and morphological data for these species. Both species are abundant and occur sympatrically over extensive areas of Texas (Davis, 1974). MATERIALS AND METHODS-Cottontails were obtained during March, 1981 from allopatric populations at two locations in Texas. Sylvilagus audubonii (n = 22) was collected from Hudspeth Co. (31°52'N, 105°10'W). Sylvilagus floridanus (n = 24) was collected from Hudspeth Co. (31°51'N, 97°21'W). Collections were made at night by spot-lighting and using a 20 ga. shotgun. Cottontails were aged as adult or subadult by examination of supraoccipital-exoccipital suture fusion. Seven S. audubonii and three S. floridanus were identified as subadults and were not used in the morphological statistical analyses. Samples of liver, kidney, and heart were taken from each animal. Blood samples were taken in heparinized blood tubes immediately after collections and stored on ice until separated into