Phylogenetic Systematics and Evolution within the Family Scincidae
Scincidae (skinks) comprise one of the largest families of lizards, and the more than 1300 species show great variation in body size and form, and are found worldwide in a diversity of habitats. The group presents many interesting questions ranging from the colonization of oceanic islands, to the e...
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| Format: | Others |
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BYU ScholarsArchive
2004
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| Online Access: | https://scholarsarchive.byu.edu/etd/1133 https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2132&context=etd |
| Summary: | Scincidae (skinks) comprise one of the largest families of lizards, and the more than 1300 species show great variation in body size and form, and are found worldwide in a diversity of habitats. The group presents many interesting questions ranging from the colonization of oceanic islands, to the evolution of limb loss, yet most of these and other questions remain understudied. The purpose of this dissertation is to use multiple mitochonidrial and nuclear DNA markers in connection with current cladistic methods to address evolutionary questions at many levels within Scincidae. In chapter one, a molecular phylogenetic study, based on six genes and extensive analyses support Cordylidae+Xantusiidae as its sister group, and confirm the paraphyly of Scincinae. The Acontinae is the sister group to all remaining skinks, while Feylininae is nested within an otherwise monophyletic southern African scincine clade. Limited support for reversal of limb and digit loss is found. In chapter two, the monophyly and relationships of Malagasy scincines are investigated using data from seven gene regions. Malagasy scincines are monophyletic, and derived from a single colonization from southern Africa. Our analyses confirm the paraphyly of Amphiglossus, and support Madascincus as a valid genus. Madascincus is sister to a monophyletic Paracontias, while Voeltzkowia is basal to the remaining Amphiglossus and Pygomeles. Chapter three uses seven gene regions to infer relationships within South American Mabuya, and to test the hypothesis of two independent colonizations from Africa to the New World. Direct Optimization (DO) is compared with traditional alignment methods, and multilocus maximum likelihood and Bayesian methods are used to date divergence times within the group. Results show that DO consistently finds more optimal tree topologies regardless of the optimality criterion used, and provides the ability to use models throughout the alignment and tree reconstruction process. South American Mabuya are not monophyletic, and the two colonization hypothesis is confirmed with parametric bootstrapping. Within the mainland species of Mabuya, many taxonomic problems are uncovered including multiple species complexes. Due to the lack of reliable fossil information, dating methods differ greatly in their estimates of divergence dates within Mabuya. |
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