Geographic Comparison of Microhabitats Used by Three Heteromyids in Response to Rarefaction

Removal trapping was used to study lability in microhabitat use by three heteromyid rodents in three widely separated localities. Among all sites, captures from the first night of trapping showed a similar pattern of microhabitat use: Dipodomys merriami was associated with open, sandy microhabitats, whereas Perognathus formosus and Perognathus longimembris were trapped in shrubby areas with, respectively, low and high percentages of sand. Continued removal of individuals (rarefaction) initiated shifts in microhabitats used by Perognathus at the Fallon Site; both species began to frequent the open areas previously occupied by Dipodomys alone. No shifts were detected at the other two sites although trapping was continued at Indian Springs for a much longer period and many more individuals were removed. Site-specific responses to rarefaction suggest that the processes underlying patterns of microhabitat use by rodents may vary geographically. These results weaken the widespread notion that localized studies can be extrapolated to generalizations of community organization over a broad area even when the same species comprise local assemblages.