Phylogeny of lacertid lizards (Squamata: Lacertidae) and the evolution of unisexuality

grantor: University of TorontoAn overall phylogeny of the Family Lacertidae was inferred from a parsimony analysis, using DNA sequence data from six mitochondrial genes. A total of 31 lacertid species were included, which represented most of the main lineages. The lacertids grouped into two clades, which correspond to the current subfamilies Lacertinae and Gallotiinae. The Lacertinae was further divided into two groups, the African and Eurasian groups. The relationships within the two groups were largely unresolved despite the large number of informative characters. A recent explosive speciation hypothesis was invoked to explain the lack of resolution from this analysis. The ancestors of the African and Eurasian groups experienced multiple simultaneous speciation events which left few or no fixed characters on the internodes making the phylogenetic reconstruction difficult. A special phenomenon, unisexuality, in lacertids was closely examined. A parsimony analysis of DNA sequence data from four mitochondrial genes was conducted to establish a firm phylogenetic foundation for the Caucasian rock lizards, among which the unisexual lacertids originated from interspecific hybridization. All bisexual species clustered into three major clades. The hybridization that led to unisexuals were of inter-clade and only occurred between the 'caucasica' and the 'rudis' clades. Moreover, these hybridization events are directional: the 'caucasica ' group only contributed to maternal parents while the 'rudis ' group to paternal parents. The formation of unisexuality is clearly under phylogenetic constraints. The causative agents of the constraints are likely multi-functional complexes, although sex chromosomes may play an important role. The divergence of cytochrome-b and ATPase 6 genes in the maternal parental species, 'Lacerta raddei' and 'L. mirta', as well as all seven known unisexual daughter species was investigated. All unisexuals constantly showed very little or no variations comparing to the substantial divergence in 'L. raddei', but 'L. mixta' showed little variation as well. A phylogeny of the mtDNA haplotypes inferred from parsimony analysis suggested that some unisexual species (clones) from the same parents shared a common ancestor while others did not. The formation of unisexual species in lacertids involved single origin, multiple origin with closely related females, as well as multiple origin with distantly related females.Ph.D