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Lanzetti A, Coombs EJ, Portela Miguez R, Fernandez V, Goswami A. The ontogeny of asymmetry in echolocating whales. Proc Biol Sci 2022; 289:20221090. [PMID: 35919995 PMCID: PMC9346347 DOI: 10.1098/rspb.2022.1090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/12/2022] [Indexed: 12/14/2022] Open
Abstract
Extreme asymmetry of the skull is one of the most distinctive traits that characterizes toothed whales (Odontoceti, Cetacea). The origin and function of cranial asymmetry are connected to the evolution of echolocation, the ability to use high-frequency sounds to navigate the surrounding environment. Although this novel phenotype must arise through changes in cranial development, the ontogeny of cetacean asymmetry has never been investigated. Here we use three-dimensional geometric morphometrics to quantify the changes in degree of asymmetry and skull shape during prenatal and postnatal ontogeny for five genera spanning odontocete diversity (oceanic dolphins, porpoises and beluga). Asymmetry in early ontogeny starts low and tracks phylogenetic relatedness of taxa. Distantly related taxa that share aspects of their ecology overwrite these initial differences via heterochronic shifts, ultimately converging on comparable high levels of skull asymmetry. Porpoises maintain low levels of asymmetry into maturity and present a decelerated rate of growth, probably retained from the ancestral condition. Ancestral state reconstruction of allometric trajectories demonstrates that both paedomorphism and peramorphism contribute to cranial shape diversity across odontocetes. This study provides a striking example of how divergent developmental pathways can produce convergent ecological adaptations, even for some of the most unusual phenotypes exhibited among vertebrates.
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Affiliation(s)
- Agnese Lanzetti
- Department of Life Sciences, Natural History Museum, Cromwell Road, Kensington, London SW7 5BD, UK
| | - Ellen J. Coombs
- Department of Vertebrate Zoology, Smithsonian National Museum of Natural History, PO Box 37012, MRC 108, Washington, DC 20013-7012, USA
| | - Roberto Portela Miguez
- Department of Life Sciences, Natural History Museum, Cromwell Road, Kensington, London SW7 5BD, UK
| | | | - Anjali Goswami
- Department of Life Sciences, Natural History Museum, Cromwell Road, Kensington, London SW7 5BD, UK
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Gray H, van Waerebeek K, Owen J, Collins T, Minton G, Ponnampalam L, Willson A, Baldwin R, Hoelzel AR. Evolutionary drivers of morphological differentiation among three bottlenose dolphin lineages, Tursiops spp. (Delphinidae), in the northwest Indian Ocean utilizing linear and geometric morphometric techniques. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Local adaptation and adaptive radiations are typically associated with phenotypic variation suited to alternative environments. In the marine environment, the nature of relevant ecological or environmental transitions is poorly understood, especially for highly mobile species. Here we compare three genetic lineages in the genus Tursiops (bottlenose dolphins), using linear measurements and geometric morphometric techniques, in the context of environmental variation in the northwest Indian Ocean. Cranial morphology was clearly differentiated comparing Tursiops truncatus and Tursiops aduncus, while a recently discovered genetic lineage, found in the Arabian Sea, was morphologically most similar to T. aduncus from the same region, but distinct for various measures, particularly metrics associated with the lateral dimension of the skull. The extent of divergence between T. truncatus and T. aduncus compared to differences between the T. aduncus lineages is consistent with the recent phylogeny for these species. Therefore, with the corroboration of genetic and morphological inference, we propose two conservation units of T. aduncus be recognized in the region at a sub-specific level so that their conservation can be managed effectively. We consider possible evolutionary mechanisms associated with regional habitat characteristics and the exploitation of distinct prey resources.
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Affiliation(s)
- Howard Gray
- Department of Biosciences, University of Durham, South Road, Durham DH1 3LE, UK
| | | | - Joseph Owen
- Department of Archaeology, Simon Fraser University, Education Building 9635, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Tim Collins
- Wildlife Conservation Society Ocean Giants Program, 2300 Southern Boulevard, Bronx, NY 10460-1099, USA
| | - Gianna Minton
- Megaptera Marine Conservation, 2242PT Den Haag, The Netherlands
| | | | - Andrew Willson
- Future Seas Global SPC, PO Box 286, Postal Code 116, Muscat, Sultanate of Oman
| | - Robert Baldwin
- Five Oceans Environmental Services, PO Box 660, PC131, Ruwi, Sultanate of Oman
| | - A Rus Hoelzel
- Department of Biosciences, University of Durham, South Road, Durham DH1 3LE, UK
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