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Dr
Sarah A Smith Smith, S.A. (2000). A molecular phylogenetic study of the Eugongylus group of skinks. Ph. D Thesis, Adelaide University, Adelaide, Australia. The Eugongylus group of skinks includes ~40 genera distributed throughout the Southern Hemisphere, and is one of five lineages of scincid lizards that are the only reptiles to have evolved complex placentation. Two of the four placental types described in reptiles only occur in the Eugongylus group. However, there is no overarching phylogenetic hypothesis for the Eugongylus group taxa. I used nucleotide sequences from mitochondrial genes (ND4 and 12S rRNA), nuclear exons (c-mos and rag-1), and introns (b -fibrinogen and cardiac myosin), in addition to some previously existing allozyme datasets, for recovering phylogenies. Mitochondrial DNA proved to be more informative than either intron or exon sequences from the nuclear genome, however there were significant problems with nuclear paralogues in two of three mitochondrial genes investigated. Exon sequences were more easily amplified than introns, and are equally informative. My first analysis focused on the overall pattern of diversification within the Eugongylus group and included taxa from Australia, New Zealand, New Caledonia, Africa and several wide-spread Pacific genera. The phylogeny suggests that the earliest divergence within the Eugongylus group was between an African lineage and a lineage which then diversified throughout the Indo-Pacific. The Eugongylus group may have diversified quickly throughout the Indo-Pacific, as each geographic region (except Australia) belongs to a single lineage. Within Australia, Hutchinson et al.'s (1990) Niveoscincus, Carlia and Lampropholis lineage is supported, but their Bassiana, Morethia, Pseudemoia lineage is not. The relationships between the lineages recovered by this analysis were not resolved with any statistical support. To further develop the phylogenetic framework for studies of placental evolution, I undertook a detailed phylogenetic analysis of the Eugongylus group lineage with the most morphologically complex placentae, the genus Pseudemoia. The phylogenetic relationships among species of Pseudemoia are recovered with high support and show that the relationships suggested by earlier allozyme studies are accurate. Chapter 5 is a phylogenetic analysis of new Zealand's endemic Eugongylus group skinks. A major reason for this study was the occurrence of a single oviparous species within the otherwise entirely viviparous endemic skink radiation. My nuclear sequence data conflicts with previously published 12S rRNA data (Hickson et al., 2000). The results presented here suggest that the phylogeny of New Zealand's endemic skinks does not include a hard polytomy as suggested by Hickson et al. (2000). My results also suggest that the only oviparous species in New Zealand is not the sister taxon to the viviparous species and, therefore, that reproductive mode in New Zealand's skink does not have a simple evolutionary history. Much of the phylogeny of the Eugongylus group is still unresolved. More exon sequence data will determine whether the polytomy at the base of the Eugongylus group tree is the result of rapid diversification, or of insufficient phylogenetic information. |