Geographical Distribution of Central American Freshwater Fishes

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Abstract
The distribution of freshwater fishes in Central America ia reviewed. Major parts of the region, especially in Honduras and Nicaragua, have yet to be explored ichthyologically, and systematic revision of important groups, notably the cichlids, is long overdue. The continental area from the Isthmus of Tehuantepec to the Colombian border contains approximately 456 spp., of which over 75% comprise the Cyprinodontidae, Poeciliidae, Cichlidae, and marine invaders (peripheral fishes); about one-third of the latter (57 spp.) have taken up more or less permanent residence in fresh water. There are 104 primary spp. in 10 families, 165 secondary forms in 6 families, and 187 peripheral spp. distributed among 30 families (nearly half of the latter are ariids, atherinids, gerrids, and gobies). Poeciliids and cichlids are particularly rich and diverse, together comprising 139 spp. Characins are numerous only in the Panamanian region, into which they and 5 South American catfish families have recently penetrated. Except for gars, no North American family has reached beyond northern Guatemala. There are no non-ostatriophysan primary fishes in the area. Although our knowledge of the fish fauna approaches adequacy only in the Guatemalan and Panamanian regions, an attempt is made to delimit fish provinces. The best known, the Usumacinta assemblage of southeastern Mexico and northern Guatemala, has been a strong center of evolution. The marked differ?ences between the fishes of this area and those of the Isthmian province, in Costa Rica and Panama, emphasize that Middle American fishes do not comprise a coherent faunal unit. Other provinces are the impoverished Chiapas-Nicaraguan and the San Juan, the latter notable chiefly for the cichlids of the Great Lakes of Nicaragua. The highlands of southeastern Mexico, Guatemala, and Honduras comprise an ancient land mass with a meager fish fauna in which the primitive cyprinodontid genus Profundulus has evolved. The Middle American fauna, from which most of Panama should be excluded, is characterized by the adaptive radiation of the probably autochthonous Poeciliidae; great diversification of the genus Cichlasoma, including the evolution of the derived genera Petenia, Neetroplus and Herotilapia; the likely origin and speciation of Bramocharax; the occurrence of numerous freshwater spp. of marine origin, a development strongly influenced by the paucity of primary freshwater fishes.