A modelling analysis of the genetic variation of phenology between tree populations

1 The phenology of temperate woody plants is commonly assumed to be locally adapted to climate. 2 However, the high gene flow expected in forest tree species, the high bet ween year variance of thermal conditions at a given place and the high plas ticity of phenology regarding temperature, lead us to hypothesize that gene tic variation of phenology between populations is likely to be insignifican t for many lowland tree species. 3 Using phenological models, we investigated variation in the timing of flo wering between locations for four European clonal tries and between differe nt populations of a further five species. 4 Models were also used to study the responses of the different populations to climate change by simulating transfers of each population to different locations. 5 While clinal variations can be observed in the phenological response to t emperature between populations, only one species (Corylus avellana) showed significantly different responses between populations and even then only on e of three populations could be separated from the others. 6 Hypothetical transfers show that the differences observed between populat ions depend on the thermal conditions at the location of transfer, and that these differences are less marked in warmer conditions. 7 Our results indicate that local adaptation will probably not be a serious constraint in predicting the phenological responses of temperate lowland t ree species to global warming.