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

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