Adaptive population differentiation in phenology across a latitudinal range in european aspen (Populus tremula L.): A comparison of neutral markers, candidate genes and phenotypic traits.

DAVID HALL; VIRGINIA LUQUEZ; VICTORIA GARCÍA; KATE ST ONGE; STEFAN JANSSON; PÄR K. INGVARSSON

EVOLUTION

Año: 2007 vol. 61 p. 2849 - 2860

0014-3820

A correct timing of growth cessation and dormancy induction represents a critical ecological and evolutionary trade-off between survival and growth in most forest trees (Rehfeldt et al. 1999; Horvath et al. 2003; Howe et al. 2003).We have studied the deciduous tree European Aspen (Populus tremula) across a latitudinal gradient and compared genetic differentiation in phenology traits withmolecular markers. Trees from 12 different areas covering 10 latitudinal degrees were cloned and planted in two common gardens.Several phenology traits showed strong genetic differentiation and clinal variation across the latitudinal gradient, with QST values generally exceeding 0.5. This is in stark contrast to genetic differentiation at several classes of genetic markers (18 neutral SSRs,7 SSRs located close to phenology candidate genes and 50 SNPs from five phenology candidate genes) that all showed FST values around 0.015.We thus find strong evidence for adaptive divergence in phenology traits across the latitudinal gradient. However, the strong population structure seen at the quantitative traits is not reflected in underlying candidate genes. This result fit theoreticalexpectations that suggest that genetic differentiation at candidate loci is better described by FST at neutral loci rather than by QST at the quantitative traits themselves.KEY WORDS: clinal variation, gene flow, genetic markers, local adaptation, population structure.