Abstract
The current taxonomy within the subgenus Profundulus was reviewed and at least five different species were recognized on the basis of unique genetic characters. Two of them are considered to be new species not yet described: one is known only from a single spring in the Tehuantepec basin (Mexico); the second extends mainly through springs in the Mixteca region of Mexico. The maximum Nei distances were found between P. oaxacae and the rest of the species belonging to this subgenus. Compared with the other Profundulus species, the new species from Mixteca also had high Nei values, which suggest separation of these species probably during the Miocene period. Therefore, the previously postulated old Central American origin of Profundulus is supported by our data. The mountain uplift that gave rise to the current division of Pacific and Atlantic rivers may be the reason for the current distribution pattern of the subgenus Profundulus . The sporadic presence of this subgenus in the headwaters of some Atlantic rivers has been interpreted as the result of fluvial captures during the Pleistocene period.