HABITAT SELECTION - AN EXPERIMENTAL FIELD-TEST WITH 2 GERBIL SPECIES

Provides experimental evidence for the isoleg theory of habitat selection in a pair of psammophilic gerbil species. Gerbillus allenbyi (mean mass: 26 g) and G. pyramidum (mean mass: 40 g) coexist in Israel's Negev Desert in areas that may contain stabilized sand fields, semistabilized dunes, and drifting dunes. When all 3 habitat types are available, coexistence between the species has been explained by a centrifugal model of community organization, untested until now. The authors conducted a field experiment in enclosures, containing similar proportions of 2 of the sandy-habitat types (stabilized sand and semi-stabilized dune), and tested the following hypotheses: 1) both species prefer the same primary habitat type; 2) G. allenbyi and G. pyramidum exhibit intraspecific density-dependent habitat selection; 3) habitat preference of both G. allenbyi and G. pyramidum is affected by the interspecific density of the other species; and 4) in the presence of the 2 habitats, habitat preferences of the 2 species should collapse from a centrifugal to a shared-preference model of habitat selection. Results supported all 4 hypotheses and allowed the construction of their isoleg graph. -from Authors