@ARTICLE{TreeBASE2Ref20819, author = {James S. Albert}, title = {Species diversity and phylogenetic systematics of American knifefishes (Gymnotiformes, Teleostei)}, year = {2001}, keywords = {South America; biodiversity; biogeography; cladistics; classification; comparative morphology; electric fishes; evolution; historical ecology}, doi = {}, url = {http://}, pmid = {}, journal = {Miscellaneous Publications, Museum of Zoology, University of Michigan}, volume = {}, number = {190}, pages = {i--127}, abstract = {Evolutionary relationships among American knifefishes are documented from comparative studies of morphological, physiological, and behavioral features. Materials were examined from more than 900 museum lots containing over 4200 gymnotiform specimens referred to 105 described and 32 undescribed species. Neural tissues were examined for 31 gymnotiform species, including representatives of 20 genera. These data were compiled into a matrix of 249 characters, including 45 characters of the nervous system, for 44 operational taxonomic units. The molecular sequence data of Alves-Gomes et al. (1995) were also analyzed, weighing transitions and transversions equally. Tree topologies from molecular sequence and morphological datasets analyzed independently using maximum parsimony are very similar, and to the topology resulting from a combined analysis. These data are used to provide phylogenetic diagnoses for 75 clades and terminal taxa, including the Gymnotiformes, 5 families,a nd 29 genera. Two new genera and 14 additional supraspecific taxa are introduced. Gymnotus + Electrophorus are found to be monophyletic, and together form the sister group to all other gymnotiforms. Rhamphichthyida + Hypopomidae and Sternopygidae + Apteronotidae are also monophyletic, the latter of which includes all species with a tone-type electric organ discharge (EOD). The fossil ?Ellisella is determined to be a member of Sternopygidae. No evidence was found for the monophyly of the nomical genera Iracema (Triques), Eigenmannia (Jordan and Evermann), Apternonotus monophyly of the nominal genera Iracema (Triques), Eigenmannia (Jordan and Evermann), Apteronotus sensu lato (Lac?pede) or Porotergus (Ellis). Megadontognathus (Mago-Leccia) and Ubidaia (Miles) are regarded as junior synonyms of Apteronotus sensu stricto (new usage) an identification key to the recognized genera is provided. The phylogenetic results permit several conclusions regarding character evolution. Sternopygus astrabes most closely resembles the ancestral gymnotiform phenotype. Two clades, Apteronotidae and Eigenmannia + Rhabdolichops possess numerous derived features, including two specialiations of the central nervous system, related to the utilization of deep river channels. Gymnotidae, Rhamphichthyidae, and Hypopomidae retain the plesiomorphic pulse-type EOD and larval hypaxial electrix organs into maturity. The tone-type EOD of Sternopygidae and Apteronotidae is derived, and the larval electric organ of these taxa degenerates at metamorphosis. Elongate snouts have evolved independently in at least four gymnotiform lineages, involving different sets of bones. The caudal fin of apteronotids is derived from the caudal appendage of other gymnotiforms, and is not an intermediate state in the loss of a caudal fin. The actual number of gymnotiform species in the wild is much greater than has previously been recognized. There are currently 108 valid species of gymnotiforms in the literature and about 34 undescribed species recognized in museum collections. These species are distributed throughout the humid Neotropics, from the Rio Salado in the Pampas of Argentina to the Rio San Nicol?s of Chiapas, Mexico. Species diversity is highest in the Amazon (89 species) followed by the Orinoco (61 species), the Guyanas (35 species), the Paran? (26 species), Northwestern South America (14 species), Southwest Brazil and Uruguay (12 species), Northeast Brazil (9 species), the Pacific slope of South America (7 species), Middle America (7 species), and the endorheic Rio Sal?-Dulce of northwestern Argentina (1 species). There are at least seven trans-Andean gymnotiform clades.} }

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