Mitogenome of the Brazilian critically endangered pitviper Bothrops insularis – structural genomic characterization and evolutionary aspects

Abstract

Abstract Background: Analyses of mitogenome structure and its evolution have provided new insights of species evolution and helped to improve in situ and ex situ conservation strategies. Although the characterization of snakes mitogenomes have been improved, the access of neotropical species molecules is still scarce, such as the case of Bothrops insularis. B. insularis is a Brazilian critically endangered snake which genomic characterization could improve information related to its evolutionary history and conservation strategies delimitation. Here we characterize for the first time the mitogenome of B. insularis, compare it with other mitogenomes available for the genus Bothrops, and used those genomes to recover the putative phylogenetic context in which the species evolved. \ Results: B. insularis mitogenome is a circular molecule with 17,523 bp length, encompassing 13 protein-coding genes, 22 tRNA, two rRNA, two control regions, one region of the light strand origin replication, a duplicate tRNA-Phe, and a non-coding region. Within the genus Bothrops mitogenomes diverge due to the presence of tRNA duplications and non-coding regions. Despite the divergences found in the mitogenome nucleotide composition and structure, evidence of positive selection was not observed in B. insularis. Comparisons among 129 snake species allowed us to identify 18 mitotypes, which originated from rearrangement processes within three tRNA clusters: the WAN-Ol-CY; the CR regions and adjacent tRNA; and the S2D cluster. These processes might have occurred in the family (Mitogenome 3B and variants), subfamily (Mitogenome 3D and variants), and species-specific levels. Conclusion: Our results provide the first description of B. insularis mitogenome, which reinforce its evolutionary significant unit status, in agreement with previous ecological, genetic, and evolutionary data. Moreover, we report a higher diversity of gene order and structure within snake mitogenomes which brings another question to be investigated: mitotypes could be correlated to habits or habitats?