Population Ecology and Genetics of the Eastern Cottontail Rabbit on West Texas Playa Basins

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Title: Population Ecology and Genetics of the Eastern Cottontail Rabbit on West Texas Playa Basins
Author: Scribner, Kim Thomas
Abstract: Spatial and temporal changes in population number , density distribution , and genetic attributes of eastern cottontails (Sylviligus floridanus ) were studied on 2 playa lake basins in the Texas Panhandle . Live -trapping was conducted from February through November , 1981 , resulting in 1 ,857 captures of 931 individuals in the course of 7450 trap nights . Seven successive litters were produced on both areas from late March through early September , 1981 . Prereproductive populations were estimated at 8 .2 and 11 .6 cottontails /ha on playa basins A and B respectively . Subsequent monthly estimates of population numbers and densities varied with reproductive increment and dispersal , which was related to crop phenology and harvest . Animals were concentrated during periods of limited cover and flooding . A sign ;ificantly (P <0 .05 ) high proportion of individuals were found on playa peripheries prior to new spring growth and during periods of dispersal than on playa basin interiors . Surrounding wheat and cotton fields provided cover and forage for dispersing animals , causing playa densities to decrease . Population increases were noted after crop harvest . Little change in adult and juvenile mortality rates occurred throughout the study , except during periods of dispersal . Spatial and temporal changes in allele frequency , genotypic proportions , and total and single locus heterozygosity were studied on both playa basins . Prereproductive adult cottontail populations had observed genotypic proportions that deviated significantly from expected Hardy -Weinberg equilibrium , seemingly the result of heterozygote deficiencies related to differential overwinter selection and /or nonrandom genotypic dispersal . These findings are inconsistent with previous studies in which heterozygosity increases were shown to correlate with superior fitness characteristics . Significant (P _ <0 .05 ) changes in population allele frequencies , genotypic proportions , and heterozygosity were related to population demographic characteristics . Apparent random matings by individual parental genotypes and subsequent juvenile recruitment dampened or eliminated the disequilibrium in Hardy -Weinberg proportions . Changes in population number due to reproductive recruitment and dispersal were accompanied by changes in gene frequency and heterozygosity . Spatial differences in population genetic attributes were maintained between the two playa basins throughout the study because of the large distances between breeding groups . However , parallel trends were observed in population genetic and demographic characteristics on both playa basins .
URI: http : / /hdl .handle .net /2346 /10662
Date: 1982-08

Citation

Scribner, Kim Thomas Population Ecology and Genetics of the Eastern Cottontail Rabbit on West Texas Playa Basins. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /10662 .

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