The role of vegetation characteristics and foraging substrate in organizing a centrifugal gerbil community

The centrifugal community organization model describes the habitat-use pattern of competing species that share a primary habitat preference but differ in their secondary habitat preferences. Our goal was to study the gradients underlying centrifugal organization in a community of 2 gerbil species, Gerbillus pyramidum (the greater Egyptian sand gerbil) and G. andersoni allenbyi (Allenby's gerbil), in the southern coastal plain of Israel. Theory suggests that the ideal combination of food and safety should occur in the semistabilized-sand habitat. However, our measurements showed that this combination actually occurs at the stabilized-sand habitat. Yet, both species prefer the semistabilized-sand habitat. By using artificial seed patches, we show that foraging at the stabilized-sand substrate is at least twice as costly as foraging at the nonstabilized substrate. This, together with potential differences in resource renewal rates and predation risk may underlie the shared-preference for the semistabilized-sand habitat and thus affect the community organization.