MITOCHONDRIAL DNA ANALYSES AND THE ORIGIN AND RELATIVE AGE OF PARTHENOGENETIC CNEMIDOPHORUS: PHYLOGENETIC CONSTRAINTS ON HYBRID ORIGINS.

Within the genus Cnemidophorus, parthenogenesis has arisen by hybridization several times. This provides the opportunity to investigate general features of hybridization events that result in the formation of parthenogenetic lineages. The relationships of mtDNA from all bisexual species of Cnemidophorus known to be parents of parthenogens were investigated to evaluate phylogenetic constraints on the hybrid-origin of parthenogenesis. No phylogenetic clustering of the parental species, either maternal or paternal, was apparent. However, the combination of bisexual species that have resulted in parthenogenetic lineages are generally distantly related or genetically divergent. This contrasts with the expectation if parthenogenesis in hybrids is due to the action of a single rare allele, but is consistent with the hypothesis that some minimal level of divergence is necessary to stimulate parthenogenetic reproduction in hybrids.