Ecological and evolutionary responses of plants to environmental change

植物种群和群落对环境变化的响应涉及生态和进化过程的相互作用。了解这些过程是一项根本性的科学挑战，并决定了我们预测和管理人类赖以生存的自然生态系统的能力。生物体的特性（例如，它们的大小或开花时间）决定了环境条件如何影响其性能。由于这些特征在物种内部和物种之间都是不同的，因此它们为评估生态进化对环境变化的反应提供了一种天然的共同货币。在物种内部，有机体反应涉及两个过程：表型可塑性，这可以使开花时间等特征对当地条件做出快速反应（例如，在一个生长季节内）；适应性进化，这需要足够的时间来进行出生和死亡，从而导致种群水平上的遗传变化。表型可塑性使我们很难追踪进化变化，而且，不同种群的可塑性反应会影响这些种群之间的基因流动，从而影响局部适应。本文提出的研究旨在评估这些过程在自然界中的作用，测试有关植物种群和群落对环境变化响应的相对未被探索的方面的关键假设。

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.