Distribution of the Gynogenetic Fish, Poecilia formosa, with Remarks on the Evolution of the Species
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American Society of Ichthyologists and Herpetologists
The species Poecilia formosa (as defined by morphological characters) is considered to be native to certain waters from the southern tip of Texas to the Laguna de Tampamachoco at the mouth of the Rio Tuxpan in eastern Mexico. Although widely distributed in the coastal lagoons, it is not present in all parts of the intervening streams. Three areas of present occurrence are considered to be due to human activity. Distribution of congeneric species in eastern Mexico is given, and evidence is presented that P. formosa arose by hybridization between P. latipinna and P. mexicana. Maternal inheritance, sibling tissue compatibility, and clonal population structure are now considered to be characteristic of the species as a whole. Although P. formosa is often stated to be an allfemale species, males are now known from four different populations, and one fertile laboratory-born male is here reported. Evidence is presented that the species arose relatively recently in the coastal lagoons, whence it spread coastwise and upstream. The native distribution of the species can be explained on the basis of present-day biological and geographic factors.