RESULTS: We re-sequenced the H. gammarus mitogenome on an Oxford Nanopore Minion flowcell and performed a long-read only assembly, generating a complete mitogenome assembly for H. gammarus. In contrast to previous reporting, we found an intact mitochondrial nad2 gene in the H. gammarus mitogenome and showed that its gene organization is broadly similar to that of the American lobster (H. americanus) except for the presence of a large tandemly duplicated region with evidence of pseudogenization in one of each duplicated protein-coding genes.
CONCLUSIONS: Using the European lobster as an example, we demonstrate the value of Oxford Nanopore long read technology in resolving problematic mitogenome assemblies. The increasing accessibility of Oxford Nanopore technology will make it an attractive and useful tool for evolutionary biologists to verify new and existing unusual mitochondrial gene rearrangements recovered using first and second generation sequencing technologies, particularly those used to make phylogenetic inferences of evolutionary scenarios.
METHODS AND RESULTS: In view of the lack of study on their mitogenome, we sequenced (by next generation sequencing) and annotated the complete mitogenome of D. vijaysegarani from Malaysia to determine its features and phylogenetic relationship. The whole mitogenome of D. vijaysegarani has identical gene order with the published mitogenomes of the genus Dacus, with 13 protein-coding genes, two rRNA genes, 22 tRNAs, a non-coding A + T rich control region, and intergenic spacer and overlap sequences. Phylogenetic analysis based on 15 mitochondrial genes (13 PCGs and two rRNA genes), reveals Dacus, Zeugodacus and Bactrocera forming a distinct clade. The genus Dacus forms a monophyletic group in the subclade containing also the Zeugodacus group; this Dacus-Zeugodacus subclade is distinct from the Bactrocera subclade. D. (Mellesis) vijaysegarani forms a lineage with D. (Mellesis) trimacula in the subcluster containing also the lineage of D. (Mellesis) conopsoides and D. (Callantra) longicornis. D. (Dacus) bivittatus and D. (Didacus) ciliatus form a distinct subcluster. Based on cox1 sequences, the Malaysia and Vietnam taxa of D. vijaysegarani may not be conspecific.
CONCLUSIONS: Overall, the mitochondrial genome of D. vijaysegarani provided essential molecular data that could be useful for further studies for species diagnosis, evolution and phylogeny research of other tephritid fruit flies in the future.