ABUNDANT MITOCHONDRIAL-DNA VARIATION AND WORLDWIDE POPULATION-STRUCTURE IN HUMPBACK WHALES

Hunting during the last 200 years reduced many populations of mysticet e whales to near extinction. To evaluate potential genetic bottlenecks in these exploited populations, we examined mitochondrial DNA control region sequences from 90 individual humpback whales (Megaptera novaea ngliae) representing six subpopulations in three ocean basins. Compari sons of relative nucleotide and nucleotype diversity reveal an abundan ce of genetic variation in all but one of the oceanic subpopulations. Phylogenetic reconstruction of nucleotypes and analysis of maternal ge ne flow show that current genetic variation is not due to postexploita tion migration between oceans but is a relic of past population variab ility. Calibration of the rate of control region evolution across thre e families of whales suggests that existing humpback whale lineages ar e of ancient origin. Preservation of preexploitation variation in hump back whales may be attributed to their long life-span and overlapping generations and to an effective, though perhaps not timely, internatio nal prohibition against hunting.