Hybridization of Karyotypically Differentiated Populations in the Sceloporus Grammicus Complex (iguanidae).

Among the approximately 60 species of the lizard genus Sceloporus, there is much karyotypic diversity, resulting primarily from the fixation of "Robertsonian rearrangements" (centric fusions and fissions; Hsu and Mead, 1969; Jackson, 1971). Diploid (2n) chromosome numbers vary from 22 to 46 (Cole, 1970, 1971; Hall, 1973), a range exceeding that known for any other lizard genus. Because comparable variation has been detected in several groups of vertebrates, including other lizard genera (Gorman and Atkins, 1968; Matthey and van Brink, 1960) and rodents (review by Nadler, 1969), and in many invertebrates, evolutionists are becoming increasingly concerned with the role of karyotypic changes in animal speciation (White, 1969; Mayr, 1969, 1970).