EVOLUTION OF STATIC ALLOMETRIES: ADAPTIVE CHANGE IN ALLOMETRIC SLOPES OF EYE SPAN IN STALK-EYED FLIES
Article first published online: 11 SEP 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 67, Issue 2, pages 453–467, February 2013
How to Cite
Voje, K. L. and Hansen, T. F. (2013), EVOLUTION OF STATIC ALLOMETRIES: ADAPTIVE CHANGE IN ALLOMETRIC SLOPES OF EYE SPAN IN STALK-EYED FLIES. Evolution, 67: 453–467. doi: 10.1111/j.1558-5646.2012.01777.x
- Issue published online: 28 JAN 2013
- Article first published online: 11 SEP 2012
- Accepted manuscript online: 18 AUG 2012 01:20AM EST
- Received December 18, 2011 Accepted July 25, 2012 Data Archived: Dryad doi:10.5061/dryad.h6q26
- evolutionary constraints;
- phylogenetic comparative method;
- phylogenetic inertia;
- sexual selection
Julian Huxley showed that within-species (static) allometric (power-law) relations can arise from proportional growth regulation with the exponent in the power law equaling the factor of proportionality. Allometric exponents may therefore be hard to change and act as constraints on the independent evolution of traits. In apparent contradiction to this, many empirical studies have concluded that static allometries are evolvable. Many of these studies have been based, however, on a broad definition of allometry that includes any monotonic shape change with size, and do not falsify the hypothesis of constrained narrow-sense allometry. Here, we present the first phylogenetic comparative study of narrow-sense allometric exponents based on a reanalysis of data on eye span and body size in stalk-eyed flies (Diopsidae). Consistent with a role in sexual selection, we found strong evidence that male slopes were tracking “optima” based on sexual dimorphism and relative male trait size. This tracking was slow, however, with estimated times of 2–3 million years for adaptation to exceed ancestral influence on the trait. Our results are therefore consistent with adaptive evolution on million-year time scales, but cannot rule out that static allometry may act as a constraint on eye-span adaptation at shorter time scales.