Genetic characterisation of the Colombian Pacific Coast humpback whale population using RAPD and mitchondrial DNA sequences

Two genetic techniques were used to characterise the humpback whale population that overwinters annually off the Pacific Coast of Colombia. A preliminary study applied molecular techniques to an initial set of 32 biopsied or sloughed skin samples. Randomly Amplified Polymorphic DNA (RAPD) was used to provide an estimate of genetic variability and intra-population structure. Diversity of RAPD banding patterns suggest substantial genetic variability among sampled individuals. A parsimony tree was constructed using presence/absence of RAPD bands as characters, revealing three distinct groups: one of closely related individuals separate from two distinct clades within which relationships were unresolved. Mitochondrial DNA sequences for a consensus fragment 283 base pair in length of the rapidly evolving mitochondrial control region were then generated for the 32 samples and an additional 48 skin samples obtained from further fieldwork. An extensive comparative analysis was made with both published and unpublished control region sequences from humpback whales previously sampled in Colombia (n=64) and other regions in the Southern hemisphere (n=193) and the North Pacific (n=21). Haplotype diversity of the Colombian humpback population was high relative to other sampled populations, with 37 distinctive haplotypes, 11 of which were represented by a single animal. Both RAPD and mtDNA sequence data suggest further genetic substructure within the Colombian Pacific Coast humpback whale population. A large proportion of haplotypes (n=17) are shared with humpback whales sampled off the Antarctic Peninsula, suggesting a strong migratory connection between these regions as reported elsewhere. Only three haplotypes were shared with other Southern Hemisphere breeding grounds. Two Colombian haplotypes were common to populations from the North Pacific, supporting the hypothesis of a past or present East Pacific gene flow corridor between Northern and Southern Hemisphere populations.