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Iterative Habitat Transitions are Associated with Morphological Convergence of the Backbone in Delphinoids


Living cetaceans are ecologically diverse and have colonized habitats ranging from rivers and estuaries to the open ocean. This ecological diversity is strongly associated with variation of vertebral morphology. Interestingly, intraspecific ecological specialization between coastal and offshore environments has also been described for several species of extant delphinoids (Monodontidae, Phocoenidae, and Delphinidae). These apparent similar ecological specialisations between and within species provide a framework to compare ecomorphological patterns below and above the species level. Here, we investigated the tempo of habitat transitions during the delphinoid evolutionary history and we quantified the effect of habitat on the vertebral morphology in all delphinoids and between bottlenose dolphin (Tursiops truncatus) ecotypes of the western North Atlantic Ocean. Our comparative analyses highlight iterative habitat transitions and associated morphological convergences of the axial skeleton in delphinoids, both occurring at high evolutionary rates. Moreover, morphological modifications between coastal and offshore bottlenose dolphin ecotypes are similar in direction and magnitude to those observed in the entire Delphinidae family. Ecomorphological patterns currently observed at the intraspecific level might reflect macroevolutionary patterns that contributed to diversification.

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The datasets generated during and/or analysed during the current study are available in the Dryad repository,


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The authors are grateful to museum curators and staff who provided access to specimens: Luc Vives from the French National Museum of Natural History; Daniela Kalthoff, Julia Stigenberg, Peter Mortensen, and Peter Nilsson from the Swedish Royal Museum of Natural History; Greg Hofmeyr, Gil Watson, and Vanessa Isaacs from the Bayworld Port Elizabeth Museum; Heather Janetzki from the Queensland Museum; Tom Geerinckx, Annelise Folie, Sébastien Bruaux, and Terry Walschaerts from the Royal Belgian Institute of Natural Sciences; Denise Hamerton, Jofred Opperman, and Noel Fouten from the Iziko South African Museum; Stefan Merker and Carsten Leidenroth from the State Museum of Natural History of Stuttgart; John Ososky, Paula Bohaska, and Darrin Lunde from the Smithsonian National Museum of Natural History. We also would like to thank Michael Collyer and Jeff Shi for input on statistical analyses and Thierry Jauniaux, Géraldine Lacave, Laurie Van Bossuyt, Krishna Das, and the Marine Mammals Science Education programme (EU grant no. 71708) for providing CT-scan of the harbour porpoise.


This project was financed through a Research Fellow grant from the Belgian Fund for Scientific Research (F.R.S.-FNRS, grant no. 24898896) and through additional travelling grants from University of Liège, F.R.S.-FNRS, Wallonia-Brussels Federation, Odyssea asbl Luxembourg, and European Union’s Seventh Framework Programme (Synthesys grant no. SE-TAF-6278) to AG.

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Amandine Gillet, Bruno Frédérich, and Eric Parmentier; conceived the project. Amandine Gillet collected and analyzed data with input from Bruno Frédérich and Stephanie E Pierce. The first draft of the manuscript was written by Amandine Gillet and all authors reviewed and edited it.

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Correspondence to Amandine Gillet.

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The authors declare they have no competing interest.

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Gillet, A., Frédérich, B., Pierce, S.E. et al. Iterative Habitat Transitions are Associated with Morphological Convergence of the Backbone in Delphinoids. J Mammal Evol 29, 931–946 (2022).

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  • Vertebral morphology
  • Convergence
  • Microevolution
  • Macroevolution
  • Cetaceans
  • Ecomorphology