Genetic analysis of the sperm whale (Physeter macrocephalus) using microsatellites.
Bond, Joanna Margaret
University of Cambridge
Department Of Genetics
Doctor of Philosophy (PhD)
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Bond, J. M. (1999). Genetic analysis of the sperm whale (Physeter macrocephalus) using microsatellites. (Doctoral thesis). https://doi.org/10.17863/CAM.11789
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The sperm whale is the largest of the toothed whales (Odontoceti), and inhabits deep waters from equatorial to Polar Regions. Sperm whales are social and commonly l r . found in small groups. However, sociality varies according to sex and age. Immature males form bachelor groups that disperse as they mature, mature males are frequently encountered alone. Sperm whales are renowned for their diving capabilities. Therefore, surface observations are only possible for 10 to 15 minutes every hour. Consequently, the sperm whale is an ideal candidate for investigation using genetic markers. Genetic variation can reveal information on geographical structuring of populations and, on a finer scale, the social organisation within these groups. The focus of this thesis is an investigation into the structure of populations around the Azores. To date, this work represents the most comprehensive molecular investigation into North Atlantic sperm whales. Since 1988 sloughed skin samples have been collected from the Azores but, to facilitate the comparison between local and global structuring, samples were also obtained from a number of geographically distinct regions. Twelve microsatellite loci and a marker to indicate sex were selected for screening. Genetic variation was sufficient to allow identification of individuals with a high degree of accuracy. A system of scoring the amplification quality was found to be both a simple and accurate method of determining the reliability of a genotype. Errors were found to arise infrequently, hence their influence in the final dataset was considered negligible. Of the 467 sloughed skin samples collected from the Azores, 102 individuals were identified. The majority of these samples had been collected from groups. As groups are presumed to be matrilineal, the identification of mother calf pairs was anticipated. However the samples revealed few parent offspring combinations. Within a group the majority of whales were related at the level of half )siblings. This indicates that I I Azorean groups comprise of individuals related through either the maternal or paternal lineage. Full siblings were also identified, which suggests that a degree of mate choice can occur. The first insight into the relationships within bachelor groups arose when two such groups, stranded off the coast of Scotland, were examined. Individuals within the groups were predominantly unrelated to each other. However, potential half/sibling relationships within the groups were identified. A mother offspring pair was identified between an Azorean whale and one of the stranded whales. Microsatellite data from Atlantic (n=I32) and Pacific (n=I59) sperm whales revealed low, but significant, inter-ocean variation. However, examinations of populations structuring on a finer scale (geographic regions) failed to reveal any consistent pattern of differentiation. This lack of differentiation is surprising when compared with other cetaceans, all of which show increased genetic differentiation with distance.
This record's DOI: https://doi.org/10.17863/CAM.11789