Mitochondrial DNA variation and maternal gene flow among humpback whales of the southern hemisphere

Samples of skin tissue were collected by biopsy darting from humpback whales (Megaptera novaeangliae) in six seasonal habitats representing three stocks and four regions: Groups IV (western Australia), V western component (eastern Australia), V eastern component (New Zealand and Tonga) and VI (the Antarctic Peninsula and Gorgona Island, Colombia, South America) of the Southern Hemisphere. A variable section of the mitochondrial DNA control region was amplified and sequenced from 84 of these individuals, distinguishing a total of 48 unique sequences (i.e., mtDNA nucleotypes). Phylogenetic reconstructions suggested that these nucleotypes form three clades, corresponding to those previously described in a world-wide survey of humpback whale mtDNA variation, although bootstrap support for two of the clades was relatively low (<50%). An analysis of variance adapted for molecular information showed significant differentiation of nucleotypes among the three Groups (Stocks) and heterogeneity of haplotype diversity among the four regions. A pattern of interchange within and between oceanic basins was demonstrated by the presence of shared identical nucleotypes among humpback whales in regions of the Southern and Northern Hemispheres.