A molecular genetic analysis of kinship in free-living groups of sperm whales.

• Main Author: Richard, Kenny Ronald.
• Other Authors: Ph.D.
• Format: Text
• Language: English
• Published: Dalhousie University 2014
• Subjects: Biology; Ecology; Genetics; Zoology; Canada; Sperm whale
• Online Access: http://hdl.handle.net/10222/55094

Mature female sperm whales (Physeter macroephalus) are found in socially cohesive groups of 10-30, including immature whales of both sexes, within which there is apparent communal care of calves. The goal of this thesis was to investigate patterns of kinship within such groups in order to better understand the genetic basis for sperm whale sociality. For the molecular genetic analysis, highly polymorphic DNA markers were developed by cloning and sequencing eleven microsatellite loci from sperm whales. Primers for polymerase chain reaction (PCR) were successfully developed for amplification of alleles at five of these loci. Additionally, primers for PCR-amplification of the male-specific SRY gene were developed for molecular sexing. The sexing data revealed that one microsatellite marker was X-linked. To investigate social structure, free-living groups of whales found off the mainland coast of Ecuador were studied with non-invasive techniques. Social groups were delineated from photographic identifications of individuals and direct observations of behavioural interactions. DNA was obtained from several samples of skin naturally sloughed by whales; a large number of samples were collected from three distinct groups. Molecular sexing showed that all groups contained mostly females. Kinship was demonstrated by the non-random distribution of microsatellite allele variation within social groups. Several indices of allele sharing were higher amongst individuals within the same group than amongst individuals in different groups. Simulation modelling suggested that the observed groups were matrilineal in structure with restricted dispersal of females. Based on the sex ratio data, males were estimated to disperse from their natal groups at about age six years. The evidence for genetic relatedness described here indicates that kin selection may have been important in the social evolution of sperm whales. Thesis (Ph.D.)--Dalhousie University (Canada), 1995.