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Population structure and diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.ORCID iD: 0000-0001-8270-7613
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Bottlenose dolphin (Tursiops sp.) populations often show small-scale genetic differentiation and have a capacity to adapt both their social strategies and structure to local environmental conditions. Here we investigate population structure and genetic diversity of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the western Indian Ocean, with special reference to Zanzibar, Tanzania. The Indo-Pacific bottlenose dolphins off Zanzibar were previously hunted and are subject to high levels of bycatch and negative impact from tourism. A recent study has indicated a limited exchange of reproducing females between northern and southern Zanzibar. Mitochondrial DNA sequence (mtDNA 429bp) variation and autosomal genotypes (7 microsatellite loci) was used to assess genetic variation and differentiation among tissue samples from Zanzibar (n=91) Mayotte (n=12) and Oman (n=4). The results showed a much higher amount of differentiation for mtDNA than autosomal DNA between northern and southern Zanzibar suggesting female philopatry with greater dispersal by males than females. Genetic diversity levels were relatively high in all areas and there were no indications of any recent reduction in effective population size, except in Mayotte where indications of a recent bottleneck encourage further analyses. Further, the close relationship and lack of clear structuring, with several shared haplotypes among regions, suggest a relatively recent common founder population for the Indo-Pacific bottlenose dolphins in the western Indian Ocean. Based on the high differentiation in mtDNA between northern and southern Zanzibar and that local growth rates in large part will be determined by female breeding success, we suggest that the Indo-Pacific bottlenose dolphins off northern and southern Zanzibar should be treated as separate management units.

Keyword [en]
Zanzibar, Tursiops aduncus, population structure, diversity, female philopatry, mtDNA, microsatellites
Identifiers
URN: urn:nbn:se:su:diva-60529OAI: oai:DiVA.org:su-60529DiVA: diva2:435663
Available from: 2011-08-19 Created: 2011-08-19 Last updated: 2014-10-13Bibliographically approved
In thesis
1. Ecology and genetic population structure of Indo-Pacific bottlenose dolphins in East Africa
Open this publication in new window or tab >>Ecology and genetic population structure of Indo-Pacific bottlenose dolphins in East Africa
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many marine mammal populations are threatened by anthropogenic activities. The Indo-Pacific bottlenose dolphins (Tursiops aduncus) off Zanzibar are subject to high levels of bycatch, negative impact from tourism and were previously hunted. To assess conservation status and to formulate necessary management actions for viable dolphin populations, knowledge of their population ecology is vital. This thesis provides information on population size, distribution, social structure, genetic diversity and population differentiation for Indo-Pacific bottlenose dolphins off southern Zanzibar. To investigate these parameters, individual identification and group structure data collected during boat based surveys were used in combination with genetic analyses of tissue samples from bycaught animals and skin biopsies from free ranging animals. The results show that the area off southern Zanzibar potentially constitute an important nursing ground (Paper I, II) for the relatively small population of Indo-Pacific bottlenose dolphins present year round (Paper I). The dolphins in this area live in a fission-fusion society where some animals also form long-term relationships (Paper II). Genetic analyses indicate limited exchange of reproducing females between northern and southern Zanzibar suggesting female philopatry with a greater dispersal by males (Paper III, IV). The relatively high genetic diversity of the Indo-Pacific bottlenose dolphins off Zanzibar indicates no current threat to their genetic health, despite recent anthropogenic impacts. (Paper IV). On a greater geographical scale the results show that the Indo-Pacific bottlenose dolphins in the western Indian Ocean, ranging from Oman to South Africa, share a relatively recent common founder population and belong to a proposed third species within the genus Tursiops (Paper III, IV). Finally, the results presented demonstrate the value of a multi-disciplinary approach to determine the conservation status of animal populations.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2011. 23 p.
Keyword
Tursiops aduncus, population size, distribution, social structure, behaviour, conservation status, mitochondrial DNA, microsatellites, Zanzibar, western Indian Ocean
National Category
Natural Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-61077 (URN)978-91-7447-293-6 (ISBN)
Public defence
2011-09-23, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript. Available from: 2011-09-01 Created: 2011-08-22 Last updated: 2011-08-24Bibliographically approved

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