View article

Despite intensive systematic study, the sexual species of the genus Cnemidophorus (Reptilia: Teiidae) have frustrated all attempts at establishing a generally accepted phylogeny at and below the species level, providing a wealth of interesting systematic problems (eg, Burt, 1931; Duellman and Wellman, 1960; Duellman and Zweifel, 1962; Walker 1981a, 1981b; Walker and Maslin, 1981; Hendricks and Dixon, 1986). Of special interest to evolutionary biologists, 13 of the approximately 44 named species are parthenogenetic forms of hybrid origin (Maslin, 1962; Lowe et al., 1970a, 1970b; Cole, 1979; Dessauer and Cole, 1986). The considerable biological variability in these cloned hybrid populations, coupled with their broad sympatry with their ancestors and other sexual species, present unusually complete model systems to study the genetic, morphological, and ecological consequences of parthenogenetic reproduction in a vertebrate. A genetically variable clonal complex can be thought of as a natural experiment that can address general questions in ecological genetics. Single genotypes are replicated in time and space, allowing an investigation of the ecological consequences of genetic variation. Furthermore, the extensive sympatric and/or parapatric" speciation" events (ie, interspecific hybridizations) that have given rise to parthenogenetic forms of Cnemidophorus allow us to study the evolution of community structure and the limiting similarity of coexisting species (Roughgarden, 1972; Vrijenhoek, 1978, 1979; Parker, 1979a; Case and Taper, 1986).