Inferring local adaptation from QSTFST comparisons: neutral genetic and quantitative trait variation in European populations of great snipe


Stein Are Sæther, Netherlands Institute of Ecology (NIOO-KNAW), Centre for Terrestrial Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands.
Tel.: +31 26 4791111; fax: +31 26 4723227;


We applied a phenotypic QST (PST) vs. FST approach to study spatial variation in selection among great snipe (Gallinago media) populations in two regions of northern Europe. Morphological divergence between regions was high despite low differentiation in selectively neutral genetic markers, whereas populations within regions showed very little neutral divergence and trait differentiation. QST > FST was robust against altering assumptions about the additive genetic proportions of variance components. The homogenizing effect of gene flow (or a short time available for neutral divergence) has apparently been effectively counterbalanced by differential natural selection, although one trait showed some evidence of being under uniform stabilizing selection. Neutral markers can hence be misleading for identifying evolutionary significant units, and adopting the PSTFST approach might therefore be valuable when common garden experiments is not an option. We discuss the statistical difficulties of documenting uniform selection as opposed to divergent selection, and the need for estimating measurement error. Instead of only comparing overall QST and FST values, we advocate the use of partial matrix permutation tests to analyse pairwise QST differences among populations, while statistically controlling for neutral differentiation.