The Molecular Evolution of Snakes as revealed by Mitogenomic Data
Snakes (Serpentes) are a diverse suborder of reptiles that, along with lizards and amphisbaenians, belong to the reptilian order Squamata. The phylogenetic position of snakes relative to lizards and amphisbaenians has been debated for about 140 years. Despite the many morphological and molecular studies that had been done, no consensus had been reached as to the phylogenetic position of snakes or on the relationships of families within Serpentes. In addition, previous molecular studies were based on only one or two genes. For my PhD I attempted to elucidate the affinities of snakes using mitogenomic data. Complete or nearly complete mitochondrial (mt) genomes were sequenced from eight snakes and two lizards. This provided a substantial amount of data for phylogenetic analysis to infer the position of snakes and to resolve the interrelationships of snake families. In addition, mitogenomic features and composition bias of mt genomes from different snake lineages were examined. The first and third papers deal with the affinities of snakes, squamate phylogeny, and the root of the squamate tree. The results support a close relationship between snakes, amphisbaenians and lacertiform lizards. The second paper is a comparative study of strand bias and base composition in the mt genomes of different snake lineages. Different snake lineages showed different trends for strand bias, suggesting that there maybe other modes of replication prevalent in the mt genomes of some snakes. The results also revealed that snakes have highly divergent composition that may explain the fast evolutionary rates of snake mt genes compared to other squamates. A phylogenetic analysis on the relationships of basal alethinophidians was performed. The results do not support some classical higher-level groupings. There is also evidence that macrostomy, the ability of snakes to increase the gape of the jaws, may be more primitive than many previous studies had suggested.
Source Type:Doctoral Dissertation
Keywords:NATURAL SCIENCES; Biology
Date of Publication:01/01/2008