Genetic variation and taxonomic analysis or the subgenus Profundulus

The current taxonomy within the subgenus Profundulus was reviewed and at le ast five different species were recognized on the basis of unique genetic c haracters. 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); t he second extends mainly through springs in the Mixteca region of Mexico. T he maximum Nei distances were found between P. oaxacae and the rest of the species belonging to this subgenus. Compared with the other Profundulus spe cies, 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 sup ported by our data. The mountain uplift that gave rise to the current divis ion of Pacific and Atlantic rivers may be the reason for the current distri bution pattern of the subgenus Profundulus. The sporadic presence of this s ubgenus in the headwaters of some Atlantic rivers has been interpreted as t he result of fluvial captures during the Pleistocene period. (C) 1999 The F isheries Society of the British Isles.