Evolution of the mitochondrial genome in snakes: Gene rearrangements and phylogenetic relationships
Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210046, PR China
BMC Genomics 2008, 9:569 doi:10.1186/1471-2164-9-569Published: 28 November 2008
Snakes as a major reptile group display a variety of morphological characteristics pertaining to their diverse behaviours. Despite abundant analyses of morphological characters, molecular studies using mitochondrial and nuclear genes are limited. As a result, the phylogeny of snakes remains controversial. Previous studies on mitochondrial genomes of snakes have demonstrated duplication of the control region and translocation of trnL to be two notable features of the alethinophidian (all serpents except blindsnakes and threadsnakes) mtDNAs. Our purpose is to further investigate the gene organizations, evolution of the snake mitochondrial genome, and phylogenetic relationships among several major snake families.
The mitochondrial genomes were sequenced for four taxa representing four different families, and each had a different gene arrangement. Comparative analyses with other snake mitochondrial genomes allowed us to summarize six types of mitochondrial gene arrangement in snakes. Phylogenetic reconstruction with commonly used methods of phylogenetic inference (BI, ML, MP, NJ) arrived at a similar topology, which was used to reconstruct the evolution of mitochondrial gene arrangements in snakes.
The phylogenetic relationships among the major families of snakes are in accordance
with the mitochondrial genomes in terms of gene arrangements. The gene arrangement
in Ramphotyphlops braminus mtDNA is inferred to be ancestral for snakes. After the divergence of the early Ramphotyphlops lineage, three types of rearrangements occurred. These changes involve translocations
within the I
QM tRNA gene cluster and the duplication of the CR. All phylogenetic methods support
the placement of Enhydris plumbea outside of the (Colubridae + Elapidae) cluster, providing mitochondrial genomic evidence
for the familial rank of Homalopsidae.