Mitochondrial genomes of five tetras and their phylogenetic implications.

To date, the taxonomic status and phylogenetic affinities within , even among other genera in Characidae, remain unclear. Here, we determined five new mitochondrial genomes (mitogenomes) of species (, , , , and ). The mitogenomes were all classical circular structures, with lengths ranging from 16,008 to 17,224 bp. The type of constitutive genes and direction of the coding strand that appeared in the mitogenomes were identical to those of other species in Characidae. The highest value of the Ka/Ks ratio within 13 protein-coding genes (PCGs) was found in ND2 with 0.83, suggesting that they were subject to purifying selection in the genus. Comparison of the control region sequences among seven fish revealed that repeat units differ in length and copy number across different species, which led to sharp differences in mitogenome sizes. Phylogenetic trees based on the 13 PCGs did not support taxonomic relationships, as the fish mixed with those from other genera. These data were combined to explore higher level relationships within Characidae and could aid in the understanding of the evolution of this group.