Electrophoretic Demonstration of the Hybrid Origin of the Gynogenetic Teleost Poecilia formosa

" The all-female gynogenetic teleost Poecia fomnosa is native to the streams and coastal lagoons of southern Texas and northeastern Mexico. In nature the species breeds with males of P. latipinna and P. mexicana in areas of sympatry (Hubbs and Hubbs, 1932; Darnel1 and Abramoff, 1968). Poecilia latipinna and P. mexicana are morphologically quite distinguishable, and P. formosa is intermediate between the two in respect to many morphological characters, such as certain scale counts, body proportions, and color patterns, as well as the size, shape, ray count, and position of the dorsal fin, etc. (Hubbs and Hubbs, 1932; Hubbs, Drewry, and Warburton, 1959; Menzel and Darnell, unpublished). On morphological, distributional, and reproductive grounds these authors suggested that the species P. formosa arose by hybridization between the two species with which it now breeds, a mode of speciation often postulated but never unequivocally demonstrated for vertebrates (Mayr, 1963). However, Uzzell and Goldblatt (1967) recently suggested that two species of Ambystoma may have arisen by hybridization "