Although the Central American oncilla is listed as a separate subspecies, based on analysis of mitochondrial DNA, Johnson et al. (1999) found strongly supported differences between "L.t. oncilla" in Costa Rica and "L.t. guttulus" in southern Brazil, comparable to differences between different neotropical species. Researchers have argued that there should be a splitting of the oncilla into two species, as there is a pronounced difference in appearance between the oncillas in Costa Rica and those in central and southern Brazil. The level of divergence between oncillas from Costa Rica and from central and southern Brazil suggests that the two populations have been isolated, perhaps by the Amazon River, for approximately 3.7 million years. Further samples of "L.t. oncilla" are needed from northern South America to determine whether this taxon ranges outside Central America, and whether it should be considered a distinct species rather than a subspecies.