Geographical variation in the morphology of the Wedge-tailed Shearwater (Puffinus pacificus)
Leigh S. BullSchool of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand. Present address: Universite Paris-Sud XI, Laboratoire Ecologie Systematique et Evolution, Batiment 362, F-91405 Orsay cedex, France. Email: leigh.bull@ese.u-psud.fr
Emu 106(3) 233-243 https://doi.org/10.1071/MU05050
Submitted: 26 September 2005 Accepted: 15 June 2006 Published: 18 August 2006
Abstract
Geographical variation in the morphology of the Wedge-tailed Shearwater (Puffinus pacificus) was assessed using multivariate analyses, including MANOVA and canonical discriminant analysis. This study tested the roles of climatic (sea surface temperature) and geographical (latitude, longitude and inter-population distance) factors as potential agents of natural selection on the body dimensions of this geographically variable species. Patterns of morphological variation, represented by phenotypic distances, were found to be unrelated to the geographical proximity of colonies. The Wedge-tailed Shearwater exhibited the trend in body size predicted by Bergmann’s Rule, increasing significantly with increasing latitude and decreasing temperature. Allen’s Rule proposes that an animal’s extremities should be relatively shorter in colder climates, but the data did not support this hypothesis with regards to variation in bill-shape of the Wedge-tailed Shearwater. Owing to the interrelated nature of ecological parameters, such as food, climate, distribution, life history and breeding biology, it is unlikely that a single factor is responsible for the observed morphological variation. However, food, through its influence on competition, dispersal, growth, fecundity and survival, may play an important role in the patterns of morphological variation found in this study. Therefore, the heterogeneity of the foraging habitat over the range of the species may be responsible for the observed variation, owing to differences in the distance required to travel to the feeding grounds and the availability and quality of food.
Acknowledgments
I thank the collection managers and curators of the bird collections in: the National Museum of New Zealand Te Papa Tongarewa (Wellington, NZ); the American Museum of Natural History (New York, USA); the National Museum of Natural History (Smithsonian Institute, Washington DC, USA); the Natural History Museum (Tring, UK); and the Australian Museum (Sydney, Australia) for access to specimens and facilities. This study was funded by the following sources: Collection study grant, the American Museum of Natural History; Hutton Fund, the Royal Society of New Zealand; Victoria University of Wellington Science Faculty grants; Helen Stewart Royle Scholarship; and the Victoria University of Wellington Postgraduate Scholarship. Thanks go to Bruce Norris and Svend Andersen for developing the computer program to calculate geographical distances, and to Ben Bell and Shirley Pledger for their advice and feedback throughout this study. Two anonymous referees provided helpful comments, which improved the paper. Many thanks go to Shirley Pledger for calculation of the Mantel’s test.
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