Variation in adaptive traits in broadleaved species - with special emphasis on climatic adaptation.

Scvcral forccs arc involvcd in dctcrlninillg tlic variation in adaptivc traits of forcst trccs. Clirnatc is assumcd to bc vcry influential, and as a coiiscqucncc clinal variation pattcrns in frost hardincss, and orisct and ccssation of growth ovcr cli~natic gradicnts liavc bccn frcqucntly rcportcd. T11c variation in adaptivc traits bctwccn adjaccrit populations, Ilowcvcr, is lcss tlian within populations in spccics studicd, but tlic ratio might dcpcnd 011 tlic spccics position in tlic ccosystcrn. Thus. lifc liistory traits such as distribution, pollination vcctor and sccd dispcrsal ability is thought to bc important, and co~nposition of tlicsc traits may partly prcdict tlic distribution of gctictic variation within and among populations. It is likcly that tl~c broadlcavcs havc a divcrsc gcnctic archilcclurc bccausc of tlic uniquc coniposition of lifc history traits of tlic individual spccics. Most nativc broadlcavcs in tlic Baltic and Nordic countrics rcacli tllcir absolutc northcrn distribution limit in this arca. With conifcrs tlicrc is littlc crnpirical support for tlic hypothesis of lcss variation in adaptivc traits ill marginal than in ccntral populatiotis, which possibly also applics for broadlcavcs. This could bc duc to variablc sclcction, and for solnc spccics, pcrliaps asy~nnictric gcnc flow. A global illcrcasc ill tcrnpcraturc is prcdictcd to incrcasc tlic distribution of broadlcavcs in Europc. at thc cxpcnsc of conifcrs. Though scvcral lifc history traits arc positivcly influcnccd by increasing summcr tcnipcraturcs, tlic ratc of tcmpcraturc changc rnay bc too rapid for adcquatc adaptation and dispcrsal of somc broadlcavcd spccics.