Clinal genetic variation and phenotypic plasticity in leaf phenology, growth and stem form in common ash (<i>Fraxinus excelsior</i> L.)

Abstract Genetic variation and phenotypic plasticity play a role in determining the performance of tree provenance at planting site. This paper explores their relative importance growth, phenology form broad geographic sample 42 British provenances common ash (Fraxinus excelsior L.) grown two contrasting trial sites. We found significant genetic differences for height, timing leaf flushing senescence, stem forking among provenances. These followed clear latitudinal climatic cline, where northern were shorter, leaves flushed later senesced earlier than southern Provenance explained much larger proportion variance spring (63 per cent) autumn (15 cent). The effect site was between autumn: showed very little plasticity, while presented higher levels plasticity. could indicate that is under stronger selective pressure. correlation forking, with early tending to be taller more forked, which reflect repeated frost damage. findings underline complexity predicting novel environments demonstrate small gains growth may counteracted by detrimental effects on form, key contributor timber value, due susceptibility contemporary environment.