Convergence in morphological patterns and community organization between Old and New World rodent guilds.

We studied morphological relationships within three guilds of gerbillid rodents in Israel. We found a nonrandom pattern of overdispersed means (community-wide character displacement) for upper incisor widths among the species in these three guilds. Upper tooth-row lengths, condylo-basal skull lengths, and tooth-row surfaces displayed similar patterns. We also studied seed-size selection by two well-studied gerbil species, which have previously been found to compete, in order to test whether specializing on husking seeds of different sizes as a mechanism of coexistence may underlie the morphological patterns. The seed-size selection experiments took place in two large aviaries with artificial lighting simulating full-moon nights, which is when predation risk is perceived as high. Seeds of different sizes (commercial seeds in one experiment and husked wheat particles in the other) mixed with sand were offered in trays. The larger Gerbillus pyramidum took significantly larger commercial seeds and marginally larger wheat particles than the smaller Gerbillus allenbyi. The patterns attest to ecomorphological convergence at the guild level; we previously demonstrated size structuring in several North American heteromyid rodent guilds, and we now report similar size structuring among Israeli gerbillid guilds. The occurrence of convergent community structure strongly indicates general rules governing ecological communities or guilds.