Ecological and evolutionary responses of plants to environmental change

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The responses of plant populations and communities to environmental change involve interactions between ecological and evolutionary processes.  Understanding these processes presents a fundamental scientific challenge and determines our ability to predict and manage the natural ecosystems upon which people depend.  The traits of organisms (e.g., their size, or time of flowering) determine how environmental conditions influence performance.  Because such traits vary both within and among species, they provide a natural common currency for assessment of eco-evolutionary responses to environmental change.  Within species, organismal responses involve two processes: phenotypic plasticity, which can allow traits such as flowering time to respond rapidly to local conditions (e.g., within a single growing season), and adaptive evolution, which requires sufficient time for birth and death to result in genetic change at the population level.  Phenotypic plasticity complicates our ability to easily track evolutionary change explicitly through time, and moreover, plastic responses in different populations can influence gene flow between those populations, and thus local adaptation.  The research proposed here aims to assess the action of these processes in nature, testing key hypotheses concerning relatively unexplored aspects of plant population and community responses to environmental change. I propose three lines of inquiry based on the plant populations and communities of the deciduous-to-boreal forest gradient with elevation in southern Québec: (1) Assessing the determinants of the relative roles of species turnover, phenotypic plasticity and local adaptation in creating community-level trait-environment matching.  This will be achieved using an in-depth observational study of above- and below-ground plant traits, within and among species, coupled with reciprocal-transplant experiments across elevations in 4-5 herbaceous species. (2) Testing the hypothesis that warming causes divergence in flowering time among populations at different elevations, thereby reducing gene flow, and affecting adaptive evolution. This project involves intense observations of flowering phenology along the gradient, molecular-marker analyses of gene flow, and experimental assessment of the performance of offspring derived from intra- and inter-population mating. (3) An explicit test for genetically-based evolutionary change in sugar maple (the dominant deciduous tree) over the period of maximal warming (the past 50 years) using an innovative combination of a `common garden across time' (generated via cuttings from trees of different age) and molecular analysis of genes with known links to climate associations. This research promises new and unique insights into biotic responses to environmental change, one of the most pressing current scientific challenges.