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Genetics and stable isotopes reveal non-obvious population structure of bottlenose dolphins (Tursiops truncatus) around the Balearic Islands

Abstract

The effective management of wildlife requires that populations are defined in a biological sensible manner. We investigated the population structure of bottlenose dolphins (Tursiops truncatus) in waters around the Balearic archipelago using two complementary techniques; DNA markers (i.e. microsatellites and a portion of the mitochondrial control region) and stable isotopes (δ13C, δ15N). We used tissue samples from biopsies (n = 50) and fresh carcasses (n = 7) obtained around the islands of Gimnèsies and Pitiüses, and Comunitat Valenciana (Western Mediterranean Sea). Genetic differentiation between individuals from Gimnésies and Pitiüses and between individuals from across these two areas and individuals from Comunitat Valenciana was significant when assessing FST, but no substructure was found using clustering methods (i.e. DAPC and Bayesian clustering). δ13C and δ15N profiles were not significantly different between dolphins from Gimnésies and Pitiüses. Dolphins from both areas showed coastal carbon isotopic values and similar trophic niche levels. However, the trophic niche of dolphins from Gimnésies was broader than the trophic niche of Pitiüses’ dolphins. These results indicate non-obvious population structure between the mainland and the archipelago, or between islands within the archipelago. The use of combined techniques, which integrate information over different time scales, is applicable to other species and areas.

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Acknowledgements

This study has been financially supported by FEP (Fondo Europeo de Pesca) European funds. Obtaining biopsies would have been impossible without the excellent work of Alex, Jorge, Yann, Santi and Tomeu, from the surveillance team of the marine reserves of the DGMRM (Direcció General de Medi Rural i Marí) in the Balearic Islands and E. Minués, J. Jiménez, and the Serra Gelada reserve’s staff in the Comunitat Valenciana. P. Gozalbes and T. Raga from the University of Valencia provided us selflessly with samples from strandings. The support by the DGMRM has been essential for the collection and analysis of data. Thanks to J.M. Valencia, M. Cerdá, E. Alvarez, A. M. Grau, and A. Frau for their help. The authors also thank the Scientist-Technical Services (University of the Balearic Islands) for collaboration in isotopic analysis and especially the support offered by B. Martorell. Many thanks for logistic support in preparing samples for isotopic analysis from P. Sarriera and F. Fuster and T. Amengual especially in the lipid extraction process. Authors thank M. Compa for assistance with the statistical R Programming Environment. Thanks to the two anonymous reviewers that contributed to an improved manuscript and to Dr. Alex Sansom for comments on the writing. Finally, thanks for the valuable supervision, support and generosity of Dr Luke Rendell.

Funding

This study was funded by FEP (Fondo Europeo de Pesca; Grant Number FEP 311NBAL00002).

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Correspondence to José M. Brotons.

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Brotons, J.M., Islas-Villanueva, V., Alomar, C. et al. Genetics and stable isotopes reveal non-obvious population structure of bottlenose dolphins (Tursiops truncatus) around the Balearic Islands. Hydrobiologia 842, 233–247 (2019). https://doi.org/10.1007/s10750-019-04038-7

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Keywords

  • Cetacean
  • Western Mediterranean
  • Microsatellite
  • Mitochondrial DNA
  • SIA
  • Trophic niche