Genetic diversity and its ecological correlates in nature: comparisons between subterranean, fossorial, and aboveground small mammals.

We have reanalyzed the levels of observed heterozygosity based on old and new material of small mammals in attempt to retest the environmental theory of genetic diversity or the niche-width variation hypothesis. This study involves old and new material of 184 small mammalian species both insectivores and rodents; 111 living aboveground and 73 species living partly (fossorial, N = 28) or totally (subterranean, N = 45) underground. The results indicated that (i) in general, insectivores harbor significantly lower levels of heterozygosity than rodents, and (ii) both overall, and in insectivores and rodents separately, the narrow-niche fossorial and subterranean species displayed significantly lower levels of observed heterozygosity than small mammalian species living aboveground. This is true in almost all parametric and nonparametric analyses. Subterranean and fossorial small mammals are more homozygous in protein diversity, primarily isozymes, compared with aboveground species. This pattern corroborates the environmental theory or niche-width variation hypothesis of genetic diversity.