Mitochondrial DNA Analyses and the Origin and Relative Age of Parthenogenetic Cnemidophorus: Phylogenetic Constraints on Hybrid Origins

Abstract

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.

Apparent Hybridization between Cnemidophorus gularis and Cnemidophorus septemvittatus from an Area of Sympatry in Southwest Texas

“…However, the uncorrected distance (Table 2) between tigris and inornatus (15.5%), tigris-gularis septemvittatus (13.7%), inornatus-gularis Iseptemvittatus (11.4%), and inornatus-sexlineatus (9.6%) are in sharp contrast to levels within gularis-septemvittatus (2.9 to 0.34%). Thus the divergence between these latter two taxa is closer to that reported between a parthenoform and bi-parental progenitor than between species (Moritz et al, 1992). Indeed, laredoensis, a parthenoform originating from female gularis mating with male sexlineatus, has approximately equal divergence to that between any gularis or septemvittatus.…”

EVOLUTIONARY ASSOCIATIONS OF BROOD PARASITIC FINCHES (VIDUA) AND THEIR HOST SPECIES: ANALYSES OF MITOCHONDRIAL DNA RESTRICTION SITES

“…A lack of difference or a very low genetic distance « 1%) in molecular genetic profiles between species has also been reported in a few other birds (Kessler and Avise 1984;Shields and Helm-Bychowski 1988;Avise et al 1990;Zink et al 1991;Seutin et al 1995). The sharing of haplotypes can be interpreted as due to (1) genetic polymorphisms that are retained from an ancestral population (Tajima 1983;Moran and Kornfield 1993;Avise 1994;Moore 1995); (2) independent gains or losses of certain restriction sites in different lineages (Aquadro and Greenberg 1983;Templeton 1983;Moritz et al 1987); or (3) hybridization and introgression of mtDNA between species (Moritz et al 1992;G. R. Smith 1992;Avise 1994;Moore 1995).…”

“…R. Smith 1992;Moore 1995), that is, if there were any cases of large genetic distances (similar to levels found in host species) between mtDNA haplotypes within the indigobirds, as these might trace ancient speciation events. In some lizards, the remote relationships between species that later hybridized to form parthenogens are reflected in mitochondrial markers of distant past speciation and differentiation that are carried by the parthenogens (Moritz et al 1992). However, within the indigobirds all mitochondrial haplotypes were very similar in restriction site profiles and none involved genetic distances comparable to those observed between the host species, as would be expected if there were survivors of past ancient cospeciations with host species.…”

“…As an alternative to colonization, a hypothesis of cospeciation and subsequent hybridization could account for the observed sharing of haplotypes among the species of indigobirds. This hypothesis might be supported if haplotypes were shared between phylogenetically remote lineages of species (Moritz et al 1992;G. R. Smith 1992;Moore 1995), that is, if there were any cases of large genetic distances (similar to levels found in host species) between mtDNA haplotypes within the indigobirds, as these might trace ancient speciation events.…”

The Evolution of Unisexuality in Calligrapha Leaf Beetles: Molecular and Ecological Insights on Multiple Origins via Interspecific Hybridization

“…In other groups, many unisexual species are known to have multiple origins, a fact that further explains high genetic diversity and phenotypic variation within these taxa (Vrijenhoek 1998;Simon et al 2003). Support for multiple origins would have been provided by species-level unisexual polyphyly (Funk and Omland 2003), that is, gene trees in which the different alleles from a unisexual species are most parsimoniously interpreted as having independent origins, rather than exhibiting the monophyly indicative of single origins (Moritz et al 1992).…”