Socio-genetic structure of southern Australian bottlenose dolphins (Tursiops cf. australis) in a South Australian embayment.

Author:

Diaz Aguirre, Fernando, 2017 Socio-genetic structure of southern Australian bottlenose dolphins (Tursiops cf. australis) in a South Australian embayment., Flinders University, School of Biological Sciences

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Abstract

Bottlenose dolphins live in complex and dynamic fission-fusion societies which are shaped by a combination of ecological, behavioural and genetic factors. However, how these factors interact and promote the emergence of such social complexity is still poorly understood. This thesis explores the social structure and sex-specific patterns of affiliation, genetic relatedness and kinship relationships of southern Australian bottlenose dolphins (Tursiops cf. australis) inhabiting a small, South Australian embayment. Photo-identification data and biopsy samples were collected in Coffin Bay between 2013 and 2015 through systematic boat-based surveys along pre-determined transect lines within a 123km2 of heterogeneous habitat encompassing different semi-enclosed bays and channels. Based on data from 657 groups of dolphins, I used recently developed generalized affiliation indices (GAI), which takes into account the effects of structural factors that confound social analyses (e.g. home range overlap, differences in gregariousness and number of sightings), in combination with a set of nuclear microsatellite markers and mtDNA sequences, to investigate dolphin affiliations, genetic relatedness and kinship relationships at population, and sex-specific levels within Coffin Bay. Chapter one provides background on animal societies and the interplay of ecological, behavioural and genetic factors, focusing on dolphin societies, and outlines the specific aims of the thesis. In chapter two, I investigated the social structure, genetic relatedness and kinship relationships at the population level using clustering and social network techniques based on GAI. I found that dolphins inhabiting Coffin Bay are structured into two well defined communities that differed in ranging and affiliation patterns, and demonstrated that genetic relatedness and kinship relationships appears to influence the social structure of this population. In chapter three, I explored male social bonds, genetic relatedness and kinship relationships, and found that male dolphins form small groups (2-5 individuals) of preferred affiliates that generally differ in their ranging patterns. The strength of these male preferred affiliations was found to be correlated with matrilineal kinship. In chapter four, I investigated the affiliation patterns, genetic relatedness and kinship relationships of female dolphins inhabiting Coffin Bay. I found that females form clusters of preferred affiliates that, similar to the males, also differ in their ranging patterns. Moreover, I found a correlation between the strength of the affiliations and the reproductive condition of females, as well as their genetic relatedness. In chapter five, I discuss factors that may explain the patterns of associations observed at the population and sex-specific levels in relation to the demography of this population, its social environment, and genetic structure, and the ecological conditions of Coffin Bay. Furthermore, I discuss and compare the results of the present study with theories for the formation of social bonds in mammals, and in that context I suggest that ecological as well as intrinsic factors such as demography, sex ratio, sexual size dimorphism and the availability of relatives within communities may have promoted the patterns of affiliations, genetic relatedness and kinship observed in this population.

Keywords: dolphins, social structure, kinship, genetic relatedness, social bonds, males, females, bottlenose dolphins
Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: Luciana Moller