School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Am Nat. 2011 Sep;178(3):411-8. doi: 10.1086/661242.
The relationship between resident species diversity and invasion is generally negative in experimental studies but takes various forms in observational studies of natural communities. We hypothesized that stochastic species colonization, which applies to natural communities but not to experimental communities generally assembled through simultaneous species introduction, may lead to nonnegative diversity-invasion relationships via incurring priority effects. To test this hypothesis, we manipulated both resident species diversity and colonization history in sequentially assembled communities of bacterivorous protist species. We found that, despite a significant effect of assembly history on invader abundance, invader abundance decreased with diversity. This result was largely driven by positive selection effects associated with the dominant influence of an invasion-resistant species, which shared the most similar resource use pattern with the invader, and by the overall weak priority effects observed for the resident communities. Increasing species diversity, however, significantly strengthened priority effects, providing the first experimental support for the idea that larger species pools promote alternative community states. We suggest that elucidating mechanisms regulating the strength of priority effects may help in understanding variation in diversity-invasion relationships among natural communities.
在实验研究中，居民物种多样性与入侵之间的关系通常是负相关的，但在自然群落的观察研究中，这种关系呈现出多种形式。我们假设，随机物种定居，适用于自然群落，但不适用于通常通过同时引入物种组装的实验群落，可能通过引发优先效应导致非负的多样性-入侵关系。为了检验这一假设，我们在通过顺序组装的噬菌性原生动物物种群落中操纵了居民物种多样性和定居历史。我们发现，尽管组装历史对入侵物种丰度有显著影响，但入侵物种丰度随多样性的增加而减少。这一结果主要归因于与入侵抗性物种的主导影响相关的正选择效应，该物种与入侵物种具有最相似的资源利用模式，以及居民群落中观察到的总体较弱的优先效应。然而，增加物种多样性显著增强了优先效应，为更大的物种库促进替代群落状态的观点提供了第一个实验支持。我们认为，阐明调节优先效应强度的机制可能有助于理解自然群落中多样性-入侵关系的变化。
