Intraspecific variability in frost hardiness of Fagus sylvatica L.

This study investigated the intraspecific variability of frost hardiness of Fagus sylvatica. We tested for local adaptation by relating the frost hardiness of different provenances to the climatic conditions at the populations' origin and searched for genetic markers that coincided with frost hardiness. Twenty provenances of F. sylvatica were selected covering the major part of the climatic gradient within the species' range. Frost hardiness was assessed in winter and tested in a climate test chamber by exposing buds to different freezing temperatures and estimating LT (50)-values by the electrolyte leakage method. Additionally, the genotypes of all investigated provenances were analyzed using amplified fragment length polymorphism (AFLP) fingerprinting. The frost hardiness differed up to 10.3 K between provenances. In contrast to our expectation, we did not find any relationship between LT (50) and climate variables. Although the populations were not well differentiated by AFLP markers, the first PCoA axis of all loci of seven different primers was strongly related to LT (50)-values. Linear regressions showed that frost hardiness could be predicted from the presence/absence of 12 loci. The high intraspecific variation in frost hardiness revealed a high potential of this species to different climates. The ability to withstand low temperatures was neither related to the species' phylogeography, nor to the current climatic conditions of provenances. This points to a more recent evolution of frost hardiness and points to a link of frost hardiness to other characteristics (e.g., drought tolerance), which might have been subjected to other selection pressures than low temperatures.