Tests of ecogeographical relationships in a non-native species: what rules avian morphology?
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The capacity of non-native species to undergo rapid adaptive change provides opportunities to research contemporary evolution through natural experiments. This capacity is particularly true when considering ecogeographical rules, to which non-native species have been shown to conform within relatively short periods of time. Ecogeographical rules explain predictable spatial patterns of morphology, physiology, life history and behaviour. We tested whether Australian populations of non-native starling, Sturnus vulgaris, introduced to the country approximately 150 years ago, exhibited predicted environmental clines in body size, appendage size and heart size (Bergmann’s, Allen’s and Hesse’s rules, respectively). Adult starlings (n = 411) were collected from 28 localities from across eastern Australia from 2011 to 2012. Linear models were constructed to examine the relationships between morphology and local environment. Patterns of variation in body mass and bill surface area were consistent with Bergmann’s and Allen’s rules, respectively (small body size and larger bill size in warmer climates), with maximum summer temperature being a strongly weighted predictor of both variables. In the only intraspecific test of Hesse’s rule in birds to date, we found no evidence to support the idea that relative heart size will be larger in individuals which live in colder climates. Our study does provide evidence that maximum temperature is a strong driver of morphological adaptation for starlings in Australia. The changes in morphology presented here demonstrate the potential for avian species to make rapid adaptive changes in relation to a changing climate to ameliorate the effects of heat stress.
KeywordsEuropean starling Invasive Exotic Alien Tarsus length
We thank Raymond Livermore, Margaret and Tim Bennett, Justin Dittmenn, and David Geering for helping with sample collection and many agriculturalists across Australia for letting investigators work on their land. We thank Jessica Moore for laboratory assistance, Mark Richardson for field assistance and Dale Nimmo for assistance with statistical analysis. Most importantly we acknowledge the starlings that were killed to conduct this research. The project was conducted under ethics approval A53-2011 and all applicable institutional and/or national guidelines for the care and use of animals were followed. P. C. and K. L. B. were supported by Australia Research Council funding (FT0991420 and FT140100131, respectively).
Author contribution statement
A. P. A. C., M. R. E. S., K. L. B., P. C. and C. D. H. S. conceived and designed the study. A. P. A. C. collected the data. A. P. A. C. and M. R. E. S. analysed the data. A. P. A. C., M. R. E. S. and K. L. B., wrote the manuscript; all authors provided editorial advice.
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