| Summary: | Working from DNA extracted from skin naturally sloughed by free-living sperm whales (Physeter macrocephalus), I amplified and sequenced the mitochondrial control region to investigate (1) the evolution of this molecule; (2) the social organization of groups of female and immature sperm whales; and (3) the population structure of sperm whales within and among three major ocean basins. First, the DNA sequence of the control region of sperm whales was compared to that of other cetaceans. The control region was reported previously to contain sequence blocks that were highly conserved among cetaceans, and assumed to have critical functions. Comparison of the sperm whale sequence, however, demonstrated that many of the sequence blocks that had been observed to be well conserved, were very different in sperm whales, calling into question the importance of these sequence blocks in at least some cetaceans. Second, organization of three social groups of female and immature sperm whales was examined using sequences from the most variable part of the control region. Analysis of resulting haplotypes revealed that group members were related, and that the groups had a matrilineal structure. A comparison of mitochondrial data to nuclear data from the same individuals indicated that some group members may be paternally related. Finally, examination of mitochondrial haplotypes in the Pacific (N = 140), Atlantic (N = 23) and the Indian (N = 19) oceans also showed the relatedness of members of social groups. However, little genetic structure above the level of groups was evident. Almost none of the total genetic variation observed was due to differences between 3 widely-separated areas in the S. Pacific, nor to differences in the three major ocean basins. This study also revealed a lack of genetic variation in sperm whales world wide. Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
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