The scale of environmental heterogeneity relative to gene flow determines the “grain size” of the habitat and is hypothesised to drive the evolution of adaptive strategies. In fine grained environments, where spatial heterogeneity is large, the evolution of adaptive phenotypic plasticity is expected. However, under homogeneous conditions, so coarse grained environments, populations are expected to locally adapt to the prevailing conditions. The distribution of different tree species in forests generates spatial variation in the timing of canopy closure and therefore spatiotemporal variation in light penetration. The quality and quantity of the available light has been demonstrated to impose a strong selection pressure on understory forest plants. These plants need to develop early enough to avoid light limitation, but, at the same time, late enough to
avoid tissue damaging frosts. I will test to which degree variation in timing traits of understory plants (i.e. their phenology) is related to the spatial variation of the light conditions and to which degree variation in timing has evolved as an adaptation to the prevailing grain size of the light conditions. The consequences of timing evolution on competitive interactions will be studied. The project will integrate well designed correlative and novel experimental approaches and benefit from its embedding in existing large scale research platforms.