Mitochondrial DNA variation reveals cryptic species in Fenneropenaeus indicus

Fenneropenaeus indicus (H. Milne-Edwards, 1837) is a commercially important penaeid shrimp in the Indo-Pacific region. Phylogenetics of penaeid shrimps is still a debatable issue and molecular variation within the species is large. The present study focuses on phylogeography of F. indicus and the phylogenetic relationships with four other species of Fenneropenaeus by assessing mitochondrial COI sequence variation of wild F. indicus sampled from Bangladesh in comparison with other populations. Fenneropenaeus indicus in Bangladesh waters consists of a single population (AMOVA: F-ST and Phi(ST), P > 0.05), which started to expand around 39-72 kyr ago. Although a high number of haplotypes is observed, the genealogical relationships are shallow and the overall variation is much less than off Sri Lanka. The different populations from the Indian Ocean show a clear geographical pattern with three distinct evolutionary lineages or cryptic species, one in the western Indian Ocean and Thailand and two in the eastern Indian Ocean, off Bangladesh and Sri Lanka. A phylogenetic analysis of Fenneropenaeus based on COI and 16S rRNA genes revealed that different lineages within E indicus predate the speciation of other species within the genus, except for Fenneropenaeus chinensis (Osbeck, 1765). Fenneropenaeus indicus exhibited complex patterns of mtDNA and polyphyletic relationships within Fenneropenaeus, and the taxonomy needs to be re-evaluated. Our study will be helpful for management and conservation of shrimp diversity.