Genetic and social structure of Lahille’s bottlenose dolphins (Tursiops truncatus gephyreus) in the Patos Lagoon estuary and adjacent coastal waters

Author: Rodrigo Cezar Genoves

Genoves, Rodrigo Cezar, 2021 Genetic and social structure of Lahille’s bottlenose dolphins (Tursiops truncatus gephyreus) in the Patos Lagoon estuary and adjacent coastal waters, Flinders University, College of Science and Engineering

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The dolphin genus Tursiops has a cosmopolitan distribution, but the subspecies Tursiops truncatus gephyreus, which is restricted to the South Atlantic Ocean, between South Brazil and Argentina, has recently been revalidated. The Patos Lagoon estuary and its adjacent coastal waters are home to the largest known population of this subspecies, and better understanding this population can contribute to the evaluation of its conservation status. The main objectives of this thesis were to investigate the spatial use patterns of these individuals, how they are structured socially, if there is genetic structuring, as well as to understand the feeding ecology of these groups and which factors influence population structuring. In chapter I an overview of the thesis is presented, with a general introduction, hypotheses, objectives, and the main methods, results, conclusions and recommendations. In Appendix I, all the available individual data of photo-identified and cataloged dolphins of the population were gathered to, through social analyses, evaluate which factors influence social structure. Four social units were identified and these were strongly associated with the spatial and temporal use of each study area (estuary, southern adjacency and northern adjacency), and individual aggregation levels. Excluding these factors from the analysis, it was observed that the two units present in each adjacent area maintain their cohesion, while the large group that uses the estuary is subdivided into four social groups. In Appendix II, the genetic structure of the estuarine and coastal dolphins was investigated. It was found that there are two genetically distinct populations occupying different isotopic niches, one associated with the estuary and another with the adjacent coastal zone. Finally, this thesis shows that the two populations have distinct patterns of habitat use, and that this is a key factor in their structuring.

Keywords: Lahille's dolphin; social structure; population structure; genomics; habitat use; feeding ecology

Subject: Meteorology and Oceanography thesis

Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Science and Engineering
Supervisor: Luciana Möller