Diversity and distribution of mitochondrial DNA lineages among humpback whales, Megaptera novaeangliae, in the Mexican Pacific Ocean

Abstract

We investigated the mitochondrial DNA (mtDNA) diversity of humpback whales, Megaptera novaeangliae, wintering off the Mexican Pacific coast and the Revillagigedo Islands. We amplified and sequenced a variable fragment of the mtDNA control region from skin samples of 65 whales and compared these with published sequences from whales in other regional habitats. Among the Mexican humpback whales, we distinguished eight haplotypes differing by 0.31–3.75% along a consensus sequence length of 320 base pairs. A diagnostic restriction site outside the consensus sequence identified a ninth common haplotype. A phylogenetic reconstruction of the control region sequences revealed two main groupings: an AE group, which is common throughout the North Pacific, and a CF group, which is closely related to haplotypes from the southern hemisphere. We found a significant degree of geographic subdivision in the wintering grounds of the eastern North Pacific. Within Mexico, whales off the Revillagigedo Islands are weakly but significantly differentiated from those of the Mexican Pacific coast. Our data also suggest that mtDNA haplotypes are clinally distributed along the American Pacific coast and we hypothesize that the present distribution of these lineages among humpback whales in the eastern North Pacific is probably associated with weather changes after the last glaciation.

Does temporal and spatial segregation explain the complex population structure of humpback whales on the coast of West Africa?

“…evidence of temporal and geographic sub-structure has been found in other wintering grounds (Smultea 1994;Medrano-gonzález et al 1995;Brown et al 1995;Dawbin 1997). It is likely that gabon is not the final destination in the greater gulf of guinea for some individuals.…”

“…Possible explanations could be attributed to temporal and/or spatial structuring of the stock. evidence of temporal and geographic sub-structure has been found in other wintering grounds (Smultea 1994;Medrano-gonzález et al 1995;Dawbin 1997). There can also be significant differences in the timing of arrival and departure of whales from a breeding area, based on their reproductive status (Dawbin 1997), and the temporal distribution of matrilines at breeding grounds (Medrano-gonzález et al 1995).…”

Migratory destinations of humpback whales that feed off California, Oregon and Washington

“…This pattern of migration suggests a series of partially overlapping migratory corridors and destinations along the coast of North America. Such a pattern could result in a clinal distribution of mtDNA types as suggested by Medrano-Gonzalez et al (1995).…”

Population structure of nuclear and mitochondrial DNA variation among humpback whales in the North Pacific

“…Published sequences of mitochondrial DNA control region from 91 humpback whales (Baker et al 1993; Medrano‐Gonzalez et al 1995) were inspected for restriction enzyme sites that could distinguish the most common haplotypes or maternal lineages in the North Pacific Ocean. As described previously, 15 variable sites in the first 317 bp of the control region defined nine haplotypes among these 91 whales.…”

“…A complete segregation of maternal lineages is found between the Californian and southeastern Alaskan feeding grounds, confirming results from photographic comparisons. Differences between the Hawaiian and Mexican wintering grounds are also significant (Medrano‐Gonzalez et al 1995), although less marked, as are differences between the nearshore Mexican wintering grounds (the Baja Peninsula and Bahia Banderas) and the offshore Revillagigedo Islands (Socorro Island). A strong migratory connection between southeastern Alaska and Hawaii is indicated by a similarity in haplotype frequencies in these two regions.…”