Relationships in Genetic Heterozygosity and Behavior in Four Southeastern Populations of Cotton Rats (Sigmodon Hispidus)
Abstract
Relationships between behavior and genic heterozygosity
were investigated using young adult male and female cotton rats
(Sigmodon hispidus) collected from naturally occurring populations
at three main1and and one beach localities in the southeastern
United States. General activity, exploratory behavior and
agonistic behavior were measured. Genic heterozygosity was
estimated by direct count for individuals and populations by
examining allelic variation in 28 proteins detectable by starchgel
electrophoresis. Mean behavioral performance of the Florida
populations increased with increasing percent average genic
heterozygosity in exploration and aggression tests, whereas
South Carolina populations did not. Some behaviors showed a
significant association with individual heterozygosity, expressed
as the number of heterozygous loci per individual when rats
were pooled for analysis.
It is concluded that genic heterozygosity affects the performance
of behavior important to wild cotton rat survival and
reproduction. In addition, cotton rat populations from more
southern latitudes demonstrated greater behavioral performance
and genic heterozygosity than more northern populations. It
is hypothesized that behavior, genetic heterozygostiy, and corresponding
behavior-genetic relationships regulate population
size in cotton rats. A model for the genetic regulation of small
mammal populations is presented, based on the premise that
individual survival, reproductive success, and movement patterns
of cotton rats are related to genetic heterozygostiy.