Source-Sink Dynamics of Garlic Mustard Invasion at Harvard Forest 2004-2006

We are investigating the role of disturbance history, source-sink metapopulation dynamics, and genetic adaptation to different canopy environments in the invasion success of Alliaria petiolata in the New England understory. In these studies, we employ a combination of population-level experiments, metapopulation studies, and landscape-level historical analyses. We have initiated a statewide survey of forested locations to determine the presence and absence of garlic mustard with respect to major pathways of invasion via past and present habitat disturbances. More explicit spatial analyses will test whether past sites of open canopy could have acted as corridors for the spread of invasive populations to present locations. This broad analysis will enable us to evaluate the generality of emerging conclusions from our population-level studies for predicting the broad-scale factors controlling the distribution, pattern and abundance of non-native species. At the population-level, we have begun long term demographic modeling of A. petiolata and experiments to test for habitat-specific natural selection on physiological, phenological, and allocational traits in sites with different canopy structure (edge or understory). In long term demographic analyses, we will use matrix population models to determine the relative contributions of subpopulations in different habitats to forest invasion. In ongoing reciprocal transplant studies, we will asses whether the maternal source habitat of a propagule contributes to its germination and survival in contrasting habitats.本研究旨在探究干扰历史、源汇集合种群（source-sink metapopulation）动态以及对不同冠层环境的遗传适应，在大蒜芥（Alliaria petiolata）于新英格兰林下的入侵成功过程中所发挥的作用。本研究结合种群水平实验、集合种群研究与景观尺度历史分析三种方法开展相关工作。我们已启动一项覆盖全州的森林样地调查，旨在基于过往与当前的生境干扰事件，明确大蒜芥在主要入侵路径沿线的分布状况。后续将开展更精细的空间分析，以验证过去的开阔冠层样地是否曾作为入侵种群扩散至当前分布区域的廊道。此项大范围分析将帮助我们评估种群水平研究所得初步结论的普适性，进而为预测调控外来物种分布、格局与丰度的大尺度因子提供支撑。在种群尺度层面，我们已启动大蒜芥的长期种群动态建模研究，并开展实验以检验不同冠层结构（林缘或林下）样地中，生理、物候与资源分配性状是否存在生境特异性的自然选择。在长期种群动态分析中，我们将采用矩阵种群模型，明确不同生境下的亚种群对森林入侵过程的相对贡献度。在正在进行的互惠移植实验中，我们将评估繁殖体的母本来源生境是否会影响其在异质生境中的萌发与存活情况。