SREL Reprint #1793

Environmental and demographic correlates of spatial and seasonal genetic structure in the eastern cottontail (Sylvilagus floridanus)

Kim T. Scribner1 and Ronald K. Chesser2,3

1Department of Zoology, University of Georgia, Athens, GA 30602
2Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802
3Department of Genetics, and Faculty of Ecology, University of Georgia, Athens, GA 30602

Abstract: Elucidation of the complex interactions of forces that affect genetic structure within and among populations is important in the assessment of short-term viability and evolution of natural populations. We examined spatial and temporal changes in genetic, demographic, and ecologic characteristics of the eastern cottontail (Sylvilagus floridanus; n = 543) within two isolated populations inhabiting playa lake basins in the Texas Panhandle. Spatial autocorrelation and contiguous clustering analyses documented nonrandom dispersion of genotypes within both populations, during each of four consecutive seasons. Considerable seasonal variation in genotypic autocorrelative patterns and size, position, and genotypic composition of significant contiguous clusters also was observed. Genotypic structuring within playa basins was particularly evident during spring, summer, and autumn; greater randomization of genetic distributions occurred in the winter, prereproductive season. Presence of spatial associations of genotypes and changes in their position and composition over seasons were influenced by episodic exchange of individuals from genetically different populations, subsequent random mating and restoration of Hardy-Weinberg genotypic proportions in resulting offspring, and patchy distribution of habitat types within playa basins. Mantel matrix regressions, which were used to test relationships among demographic, habitat, and genotypic variables show that the relative importance of each factor changes seasonally. Differences in habitat use among individuals were significantly correlated with genotypic cluster affiliation during the prereproductive period, whereas age structure became increasingly important in explaining spatial arrangement of genotypes during later periods. Although populations from different playa basins differ in gene frequency, seasonal changes in genetic structure within each population were correlated.

Keywords: Sylvilagus floridanus, demography, genetic structure, habitat, matrix correlation, playa basin, reproduction, spatial variation, temporal variation

SREL Reprint #1793

Scribner, K.T. and R.K. Chesser. 1993. Environmental and demographic correlates of spatial and seasonal genetic structure in the eastern cottontail (Sylvilagus floridanus). Journal of Mammalogy 74:1026-1044.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).