Characterization, Comparison of Two New Mitogenomes of Crocodile Newts (Caudata: Salamandridae), and Phylogenetic Implications.

Mitochondrial genomes (mitogenomes) are valuable resources in molecular and evolutionary studies, such as phylogeny and population genetics. The complete mitogenomes of two crocodile newts, and , were sequenced, assembled, and annotated for the first time using next-generation sequencing. The complete mitogenomes of and were 16,265 bp and 16,259 bp in lengths, which both composed of 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes, and 1 control region. The two mitogenomes had high A + T content with positive AT-skew and negative GC-skew patterns. The ratio of non-synonymous and synonymous substitutions showed that, relatively, the gene evolved the fastest and evolved the slowest among the 13 PCGs. Phylogenetic trees from BI and ML analyses resulted in identical topologies, where the split into two groups corresponding to two subgenera. Both and sequenced here belonged to the subgenus , and these two species shared a tentative sister group relationship. The two mitogenomes reported in this study provided valuable data for future molecular and evolutionary studies of the genus and other salamanders.