Habitat partitioning among coexisting desert rodents: two examples of species packing


Category:  Wildlife Science
Linked Publication
Language: English
Author(s): Eric larsen
Description: Microhabitat utilization by desert rodent communities was studied in sagebrush habitats of the shrub-steppe vegetation type and in sand dunes of the Sonoran and Great Basin deserts. The micro-habitat utilizations-of Perognathus and Dipodomys were inversely related to each other in both habitats relative to the perennial vegetation. The relationship was statistically significant in sand dunes (X2 = 73.9, 6 df, P = 0.0), whereas the relationship was qualitatively apparent though not statistically significant (X2 = 7.85, 6 df, P = 0.25) in sagebrush habitats. The lack of clear microhabitat partitioning among coexisting rodents in sagebrush habitats was probably due to the high density of bushes which left little space for fine partitioning of the habitat in the horizontal dimension. Species packing theory predicts that as the number of species increases, the utilization curves of the species coexisting on a given resource should narrow. Variability in the breadth of microhabitats utilized was analyzed with multiple regression with respect to the number of coexisting species and their relative abundance in an attempt to test this theory. Variance of microhabitat utilization for D. ordii in both habitats, and for D. merriami in sand dunes, were negatively correlated with the number of coexisting heteromyid species. This result was consistent with theory. Variances of microhabitat utilization for P. parvus in sagebrush habitats were positively correla-ted with the number of coexisting heteromyid species, and variances for P. longimembris in sand dunes were positively correlated with the total number of coexisting species. Both relationships for Perognathus are contrary to the prediction of theory. Peromyscus exhibited con-trasting results in the two environments. Variances of microhabitat use were negatively correlated with the number of heteromyid individ-uals and positively correlated with the number of cricetid individuals in sand dunes. In sagebrush habitats no significant relationships were detected. A tentative explanation is offered for the contrasting results considering differences in foraging strategy and the distribution of seed resources in the desert soil.