Testing the thermal melanism hypothesis: a macrophysiological approach
Article first published online: 8 JAN 2008
© 2008 The Authors
Volume 22, Issue 2, pages 232–238, April 2008
How to Cite
Clusella-Trullas, S., Terblanche, J. S., Blackburn, T. M. and Chown, S. L. (2008), Testing the thermal melanism hypothesis: a macrophysiological approach. Functional Ecology, 22: 232–238. doi: 10.1111/j.1365-2435.2007.01377.x
- Issue published online: 8 JAN 2008
- Article first published online: 8 JAN 2008
- Received 7 September 2007; accepted 28 November 2007Handling Editor: Michael Angilletta
- skin absorptance;
- solar radiation;
- 1The thermal melanism hypothesis (TMH) predicts that dark (low skin reflectance) individuals are at an advantage in cool climates as they heat faster and reach higher equilibrium temperatures than lighter (higher reflectance) individuals. However, tests of the TMH have yielded mixed support, especially in ectothermic vertebrates.
- 2Most studies to date have been undertaken at small spatial scales or using a few, closely related populations or species. Here, we therefore examine the TMH at large scales in heliothermic lizard species, testing two of its major predictions and a corollary thereof, using standard and phylogenetically corrected analyses.
- 3First, we test the prediction that skin reflectance and climate variables such as mean annual temperature (MAT) and global solar radiation are positively related across species. Second, we determine whether a positive relationship exists between skin reflectance and body mass. Third, since physiology, behaviour and morphology should be co-adapted, we test the prediction that skin reflectance and traits of thermal biology are positively related.
- 4We find strong support for a positive relationship between skin reflectance and mean annual radiation even after adjusting for phylogeny. Moreover, radiation was a better predictor of skin reflectance than MAT. We also find support for a positive relationship of skin reflectance with body size, although this was non-significant after accounting for phylogeny.
- 5Skin reflectance was not related to measures of thermal biology, although confounding effects such as methodological differences could not be ruled out.
- 6In summary, this study provides novel support for the TMH operating interspecifically at large geographic scales, suggesting adaptive variation of skin reflectance among lizards.