Minimal genetic divergence among South American samples of the water opossum Chironectes minimus: Evidence for transcontinental gene flow?

Cytochrome b sequences from South American specimens of the water opossum Chironectes minimus exhibit uncorrected pairwise differences of 0.6% or less among samples collected thousands of kilometers apart (in Guyana, Bolivia and southeastern Brazil). Despite published evidence of population divergence from recent analyses of craniodental morphology, our results suggest extensive gene flow or recent range expansion across the South American landscapes currently occupied by this seldom-collected species.