Morphological differentiation in Carduelis finches: Adaptive vs. constraint models
Version of Record online: 11 DEC 2002
Journal of Evolutionary Biology
Volume 6, Issue 3, pages 359–373, May 1993
How to Cite
Björklund, M. and Merilä, J. (1993), Morphological differentiation in Carduelis finches: Adaptive vs. constraint models. Journal of Evolutionary Biology, 6: 359–373. doi: 10.1046/j.1420-9101.1993.6030359.x
- Issue online: 11 DEC 2002
- Version of Record online: 11 DEC 2002
- Received 16 January 1992; accepted 20 October 1992.
- Cited By
- Cardueline finches;
- multivariate analysis;
- morphological integration
In this study we show that morphological diversification in the avian genus Carduelis (Carduelinae) has to a large extent been conservative. Using multivariate methods, we found only minor deviations from the common (ancestral) body-plan. In particular, variation in bill morphology was found to be more conservative than variation in other parts of the body.
We argue that constraint models of population differentiation can successfully account for the variation in bill morphology in this genus, but are less successful in accounting for variation in other traits. This can be interpreted as a result of long-term overall stabilizing selection for a certain bill morphology which is related to the way the birds open seeds. A trait combination that is adaptive on the evolutionary time scale may thus act as a constraint on changes in bill morphology on the microevolutionary scale. We conclude that the most parsimonious explanation for low divergence in bill morphology in this genus is that all species have retained the ancestral bill morphology. This may mean that each species chooses its environment rather than being moulded by it. This argument seems to apply to bill morphology, but other traits studied in this genus appear to have evolved in a less constrained fashion. A new index of morphometric integration is introduced to describe covariance structures.