Environmental variation on a local scale creates complex habitat patchiness which contributes to the great diversity observed in tropical rainforests. For instance, the divergence in species distribution between hilltops and bottomlands is determined by variations in tolerance to drought and waterlogging. A recent paper in Annals of Botany looks at how local environmental factors shape vast tracts of rainforest.
Seedling populations native to different habitats displayed phenotypic divergence for several traits (including seedling growth, biomass allocation, leaf chemistry, photosynthesis and carbon isotope composition). This occurs through heritable genetic variation or other maternally inherited effects. The results of this study show that mother trees from different habitats transmit divergent traits to their progeny, and suggest that local environmental variation selects for different trait optima even at a very local spatial scale.