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Phenotypic Changes Across a Geographic Gradient: The Case of Three Sympatric Dolphin Species

Guidarelli, G and Colangelo, P and de Francesco, MC and Nicolosi, P and Meloro, C and Loy, A (2017) Phenotypic Changes Across a Geographic Gradient: The Case of Three Sympatric Dolphin Species. Evolutionary Biology. ISSN 0071-3260

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Abstract

Phenotypic changes in the mammalian mandible can occur at different spatial and temporal scales. We investigated mandibular size and shape variation in three extant closely related dolphins (Cetacea, Odontoceti): Tursiops truncatus, Stenella coeruleoalba and Delphinus delphis in order to test the hypothesis that similar phenotypic changes occur across the same geographical gradient. Our data included 219 specimens representative of the following geographic locations: the Mediterranean Sea, the eastern north Atlantic and the North Sea. Each mandibula was photographed laterally and spatial positioning of eight homologous 2D landmarks was recorded. After applying generalised Procrustes analysis (GPA), intraspecific variation was first investigated between sexes and among populations to allow further pooling of samples. Size and shape differences among populations and species were investigated through multivariate ordination techniques (PCA), Procrustes ANOVA and allometric analyses. In all three species, Mediterranean populations clearly differed in mandible shape from the extra-Mediterranean ones. Among the three, the direction of geographic phenotypic changes was significantly similar in the striped and common dolphin, while the bottlenose dolphin was the most divergent species, differing both in size and allometric trajectory. Shape variation of the two former species highlighted a morphological convergence in the Atlantic, and a phenotypic divergence in the Mediterranean. Shape differences among the three dolphin species were interpreted in the light of different prey preferences, feeding strategies and habitat partitioning to avoid direct competition.

Item Type: Article
Additional Information: The final publication is available at Springer via http://dx.doi.org/10.1007/s11692-017-9435-6
Uncontrolled Keywords: 0603 Evolutionary Biology
Subjects: Q Science > QH Natural history
Q Science > QH Natural history > QH426 Genetics
Q Science > QL Zoology
Divisions: Natural Sciences and Psychology
Publisher: Springer Verlag
Date Deposited: 08 Nov 2017 11:56
Last Modified: 08 Nov 2017 11:56
DOI or Identification number: 10.1007/s11692-017-9435-6
URI: http://researchonline.ljmu.ac.uk/id/eprint/7495

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