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Evolutionary Relationships of Pupfishes in the Cyprinodon eximius Complex (Atherinomorpha: Cyprinodontiformes)
Anthony A. Echelle and Alice F. Echelle
Vol. 1998, No. 4 (Dec. 30, 1998), pp. 852-865
Stable URL: http://www.jstor.org/stable/1447332
Page Count: 14
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Allozymes encoded by 30 presumptive gene loci were used in phylogenetic analyses of the Cyprinodon eximius complex (Cyprinodontidae), a group of 12 species occurring primarily on the Mexican Plateau from the states of Zacatecas and Nuevo Leon north to the Rio Grande. The most parsimonious phylogenetic tree supported the following: (1) the C. eximius complex is paraphyletic, with a clade comprising C. alvarezi and C. ceciliae from the Potosí and Sandia basins being basal relative to the pupfishes examined (including five species from outside the C. eximius complex); (2) an early event separated the Río Conchos-Rio Grande-Old Río Nazas pupfishes from a previously identified clade of eight species (the "western pupfishes") that extends from the Guzmán Basin in northwestern Chihuahua to the Death Valley system of California; (3) the ancestral C. meeki, a species from the Pacific slope, was isolated from pupfishes in the Old Río Nazas by a Pleistocene stream capture; (4) C. nazas, a species from the headwaters of the Old Río Nazas is paraphyletic with respect to C. atrorus, one of two species from Cuatro Ciénegas (this supports one of the three suggested outlets of the Old Río Nazas to the Rio Grande, i.e., the Río Salado); (5) a clade of four species occupies the Río Conchos drainage in Mexico and contiguous waters of the Rio Grande drainage (this clade includes the relatively wide-ranging C. eximius and three local endemics from spring systems in Chihuahua, C. macrolepis and C. pachycephalus, and the Pecos River in Texas, C. elegans); and (6) the two pupfishes from Cuatro Ciénegas, C. atrorus and C. bifasciatus, represent divergent lineages, the latter apparently being a relatively early product of pupfish evolution on the Mexican Plateau.