This work forms part of Jose A. Ramírez-Valiente’s PhD which is currently carrying out under the supervision of Ismael Aranda and Fernando Valladares. This is focused on the analysis of the local and evolutionary capacity of cork oak and other Mediterranean tree species by integrating molecular techniques and ecophysiological studies. Ismael Aranda is a functional plant ecologist working in the physiological response of forest tree species. Most of his studies are aimed to a better understanding of the ecological and evolutionary consequences of the functional diversity by different genetics backgrounds, ranging from the species-specific pattern to the intra-specific differentiation among populations. Fernando Valladares is a plant ecologist working in the integration of ecophysiological research with plant demography and fitness under global change scenarios. He is especially interested in the evaluation of the ecological and evolutionary significance of phenotype plasticity, as well as the ecological constraints acting on it. Alvaro Soto and Luis Gil are professors of genetic and plant anatomy in the department of “silvopascicultura” at the Polytechnique University of Madrid. Zaida R. Lorenzo is a postdoctoral fellow also at the Polytechnique University of Madrid. They share an interest in the study of genetic diversity, hybridization phenomena and conservation genetics in forest tree species.
Elucidating the role of genetic drift and natural selection in cork oak differentiation regarding drought tolerance
Article first published online: 1 SEP 2009
© 2009 Blackwell Publishing Ltd
Volume 18, Issue 18, pages 3803–3815, September 2009
How to Cite
RAMÍREZ-VALIENTE, J. A., LORENZO, Z., SOTO, A., VALLADARES, F., GIL, L. and ARANDA, I. (2009), Elucidating the role of genetic drift and natural selection in cork oak differentiation regarding drought tolerance. Molecular Ecology, 18: 3803–3815. doi: 10.1111/j.1365-294X.2009.04317.x
- Issue published online: 10 SEP 2009
- Article first published online: 1 SEP 2009
- Received 25 February 2009; revision received 14 May 2009; accepted 21 May 2009
- carbon isotope discrimination;
- leaf size;
- Quercus suber;
Drought is the main selection agent in Mediterranean ecosystems and it has been suggested as an important evolutionary force responsible for population diversification in these types of environments. However, population divergence in quantitative traits can be driven by either natural selection, genetic drift or both. To investigate the roles of these forces on among-population divergence in ecophysiological traits related to drought tolerance (carbon isotope discrimination, specific leaf area, leaf size and leaf nitrogen content), we compared molecular and quantitative genetic differentiation in a common garden experiment including thirteen cork oak (Quercus suber L.) populations across a gradient of rainfall and temperature. Population differentiation for height, specific leaf area, leaf size and nitrogen leaf content measured during a dry year far exceeded the molecular differentiation measured by six nuclear microsatellites. Populations from dry-cool sites showed the lowest nitrogen leaf content and the smallest and thickest leaves contrasting with those from humid-warm sites. These results suggest (i) these traits are subjected to divergence selection and (ii) the genetic differences among populations are partly due to climate adaptation. By contrast, the low among-population divergence found in basal diameter, annual growth and carbon isotopic discrimination (a surrogate for water use efficiency) suggests low or no divergence selection for these traits. Among-population differentiation for neutral markers was not a good predictor for differentiation regarding the quantitative traits studied here, except for leaf size. The correlation observed between the genetic differentiation for leaf size and that for molecular markers was exclusively due to the association between leaf size and the microsatellite QpZAG46, which suggests a possible linkage between QpZAG46 and genes encoding for leaf size.