Phylogenetic position of Platanista gangetica: Insights from the mitochondrial cytochrome b and nuclear interphotoreceptor retinoid-binding protein gene sequences

The evolutionary relationship of peculiar and poorly known Ganges River dolphin with extinct and extant cetaceans has been in the state of confusion for more than a century. The close resemblance of platanistidae with some of the extinct taxon viz., Dalpiaziniidae and Waipatiidae and their sister group relationship with many of the extant lineages of cetaceans has been reported but none of the alternative hypotheses provide an unambiguous placement for this species. The present study provides insights into the molecular relationships of Platanista with other cetaceans based on comprehensive analyses of the mitochondrial cytochrome b and nuclear interphotoreceptor retinoid-binding protein gene sequences, obtained from 15 specimens of Ganges dolphin from India and Bangladesh. The mean substitution distance analysis of phylogenetically informative characters in the cytochrome b sequences suggested that Platanista gangetica is significantly closer (P < 0.001) to Mysticeti than to any other group of toothed whales. However, the conventional methods of phylogenetic reconstruction supported this finding with low to moderate (41-69%) bootstrap values.