In a long-term experimental demography study, excluding ungulates reversed invader’s explosive population growth rate and restored natives

A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce new metrics to correctly integrate experimental effects across treatment years, the cumulative population growth rate, λc, and its geometric mean, λper-year, the time-averaged annual population growth rate. We determined λc and λper-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory ...

生态学的核心目标之一，是阐明提升外来物种入侵成功概率的内在机制。近期有假说提出，有蹄类食草动物过度增殖所引发的物种互作改变，是外来植物占据群落优势地位的关键诱因。为验证该假说，我们在本地有蹄类动物白尾鹿（Odocoileus virginianus）种群过度繁盛、且大蒜芥（Alliaria petiolata）正强势入侵的森林生境中，开展了为期6年的鹿排除种群动态实验。由于种群增长随时间呈乘法累积效应，我们引入了全新指标以正确整合各处理年份的实验效应：累积种群增长率λ_c 及其几何均值λ_per-year，即时间平均年种群增长率。我们分别测定了入侵种大蒜芥与常见本地植物延龄草（Trillium erectum）的这两项指标。研究结果确凿证实，鹿是大蒜芥成功入侵的必要条件，其预测种群轨迹……