Mitogenomic variation of Bangladesh Penaeus monodon (Decapoda, Panaeidae) and reassessment of its phylogeography in the Indo-West Pacific region

Abstract

Large variation in the mtDNA control region (CR) in Penaeus monodon has been reported from the Indo-West Pacific region, characterizing three distinct lineages, A, B and C. This diversification has been explained by geographic barriers but may also be due to paralogous duplication events. Here we evaluate the diversity, origin and population patterns of this species in Bangladesh based on mtDNA, and reconsider the evidence for paralogous duplication. MtDNA variation revealed high diversity with almost all individuals carrying a unique haplotype, indicating a large effective population size and a single reproductive pool. The Bangladesh haplotypes cluster within lineage C, found mainly west of the Sunda Shelf. This lineage, which diverged from lineages A and B around 6.6 Mya, has diverged further into several lineages in the western Indian Ocean. Sequences of mitochondrial CR, 16S rRNA gene and a combined fragment of the 16S rRNA and tRNAVal genes from Bangladesh did not reveal any duplication or heteroplasmy. Further, phylogenies based on the three markers, including samples from different areas in the Indo-West Pacific region, support the occurrence of three distinct lineages. Thus, the variation in CR appears to result from segregation of orthologous variants rather than diversification following a paralogous duplication.