Quantification of small mammal dispersal by genetic and demographic characters



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This study concerned the identification of dispersers in small mammal populations using genetic and demographic characters from three species of rodents, Sigmodon hispidus, Reithrodontomys fulvescens, and Oryzomys palustris. The hypotheses tested were (1) that there are no differences in the levels of heterozygosity (genetic variability) between resident and dispersing rodents and (2) that there are no correlates between movement and certain demographic parameters. A three-year Sympatric Experiment was utilized to study movement patterns and demographic parameters of Sigmodon and Reithrodontomys. Dispersers were collected along with residents at the termination of this experiment and used in the genetic analysis. A one-year Void Experiment was also utilized to collect genetic data and short term demographic data for Oryzomys and Reithrodontomys. No significant differences were found between residents and dispersers in their levels of genetic heterozygosity. No effect of heterozygosity upon distance moved was found for Reithrodontomys. Both Sigmodon and Reithrodontomys had significant positive correlations between distance moved and reproductive condition. Sex ratios were skewed towards males for Sigmodon and Reithrodontomys when analyzing animals that moved greater distances. [...]