Population genetic structure of two ecologically distinct Amazonian spiny rats: Separating history and current ecology

Population history and current demographic and ecological factors determine the amount of genetic variation within and the degree of differentiation a mong populations. Differences in the life history and ecology of codistribu ted species may lead to differences in hierarchical population genetic stru cture. Here, we compare patterns of genetic diversity and structure of two species of spiny rats in the genus Proechimys from the Rio Jurua of western Amazonian Brazil. Based on the ecological and life-history differences bet ween the two species, we make predictions as to how they might differ in pa tterns of genetic diversity and structure. We use mitochondrial sequence da ta from the cytochrome b gene to test these predictions. Although both spec ies maintain nearly the same number of mitochondrial haplotypes across the sampled range, they differ in levels of genetic diversity and geographic st ructure. Patterns of gene flow are also different between the two species w ith average M-values of nearly three in P. steerei and less than one in P. simonsi. Our initial predictions are largely upheld by the genetic data and where conflicting hypotheses arise, we suggest further studies that may al low us to distinguish among evolutionary scenarios. Separating the effects of history and ongoing demography on patterns of genetic diversity is chall enging. Combining genetic analyses with held studies remains essential to d isentangling these complex processes.