Population Differentiation of 2 Forms of Bryde’s Whales in the Indian and Pacific Oceans

Accurate identification of units for conservation is particularly challenging for marine species as obvious barriers to gene flow are generally lacking. Bryde’s whales( Balaenopteraspp.) are subject to multiple human-mediated stressors, including fisheries bycatch, ship strikes, and scientific whalingby Japan. For effective management, a clear understanding of how populations of each Bryde’s whalespecies/ subspeciesare genetically structured across their range is required. We conducted a population-level analysis of mtDNA control regionsequences with 56 new samples from Oman, Maldives, and Bangladesh, plus published sequences from off Java and the Northwest Pacific. Nine diagnostic characters in the mitochondrial control region and a maximum parsimonyphylogenetic analysis identified 2 genetically recognized subspeciesof Bryde’s whale: the larger, offshore form, Balaenoptera edenibrydei, and the smaller, coastal form, Balaenoptera edeniedeni. Genetic diversity and differentiation indices, combined with a reconstructed maximum parsimonyhaplotype network, indicate strong differences in the genetic diversity and population structure within each subspecies. Discrete population units are identified for B. e. brydei in the Maldives, Java, and the Northwest Pacific and for B. e. edeni between the Northern Indian Ocean (Oman and Bangladesh) and the coastal waters of Japan.