Echimyidae

Abstract: Sequence variation in the mitochondrial cytochrome b gene was examined in the arboreal spiny rat, Mesomys hispidus, collected at 15 sites along the Rio Jurua in western Amazonia, Brazil, to determine the importance of riverine barriers in the diversification of this taxon. Twenty individual haplotypes were uncovered, most of which were unique to single localities but some of which were shared among adjacent sites either along or across the river. Genealogical analyses suggest that gene flow is limited and, in combination with the unique distribution of most haplotypes, suggest that populations of this species are strongly substructured along the river. Thus, most sharing of haplotypes between adjacent localities is probably caused by historical association rather than to ongoing gene flow. Two haplotype clades were uncovered, but these correspond to headwaters versus mouth areas, not to opposite sides of the river, as would be expected by the Riverine Barrier Hypothesis. Moreover, haplotype sharing across the river was greater at its mouth than in the headwaters, a pattern opposite that expected if the river were a substantive barrier. Broader scale phylogeographic patterns of this species show that both clades have relationships to areas well outside the Rio Jurua basin. This suggests that the basin represents a relatively recent point of invasion between two more broadly distributed and differentiated geographic units of the species.

Abstract: The Capromyidae (hutias) are endemic rodents of the Caribbean and represent a model of dispersal for non-flying mammals in the Greater Antilles. This family has experienced severe extinctions during the Holocene and its phylogenetic affinities with respect to other caviomorph relatives are still debated as morphological and molecular data disagree. We used target enrichment and next-generation sequencing of mitochondrial and nuclear genes to infer the phylogenetic relationships of hutias, estimate their divergence ages, and understand their mode of dispersal in the Greater Antilles. We found that Capromyidae are nested within Echimyidae (spiny rats) and should be considered a subfamily thereof. We estimated that the split between hutias and Atlantic Forest spiny rats occurred 16.5 (14.8–18.2) million years ago (Ma), which is more recent than the GAARlandia land bridge hypothesis (34–35 Ma). This would suggest that during the Early Miocene, an echimyid-like ancestor colonized the Greater Antilles from an eastern South American source population via rafting. The basal divergence of the Hispaniolan Plagiodontia provides further support for a vicariant separation between Hispaniolan and western islands (Bahamas, Cuba, Jamaica) hutias. Recent divergences among these western hutias suggest Plio-Pleistocene dispersal waves associated with glacial cycles.