Multi-Species Metapopulation Dynamics: Experiments in a Model System

空间结构如何影响种群动态，栖息地破碎化如何影响生物多样性是现代生态学中最重要的两个问题。在单一物种的大种群中，或不相互作用的物种群中，栖息地的细分预计会导致全球（“大种群”）灭绝，这样，传播速度最低的物种将会灭绝得最快。相反，相互作用物种的元种群模型预测，中间程度的细分可以促进不稳定相互作用物种的共存。本研究为研究生境细分如何影响物种组合的结构和持久性提供了一个独特的机会。这项工作将在包含原生动物组合的水生微观环境中进行，其中已知成对和多物种相互作用。将检验两个可选的假设：(1)增加的细分总是降低所有物种的持久性，最弱的传播者灭绝得最快；(2)细分促进了部分或所有物种的持久性，至少达到某种中间程度的细分；这意味着物种之间的相互作用是重要的。这些假设将通过测量不同程度细分的微观世界中各种物种组合的持久性来检验。扩散速率也将被测量，这样物种灭绝的顺序就可以被记录下来。这些实验将显示群落对栖息地细分的反应是否可以从所涉及的特定物种的动态中预测，而不是从物种之间相互作用的类型和细节中预测。本研究将证明栖息地破碎化（细分）是否促进了生物多样性。特别是，这些实验将检验生态学理论中与预测生活在斑块状栖息地的濒危物种对不同程度破碎的反应最直接相关的部分。

9629876 Holyoak How spatial structure affects populations dynamics, and how habitat fragmentation affects biodiversity are two of the most important questions in modern ecology. In metapopulations of single species, or sets of species that do not interact, subdivision of a habitat is expected to cause collapse to global ("metapopulation") extinction, such that species with the lowest dispersal rates will go extinct soonest. In contrast, metapopulation models of interacting species predict that an intermediate degree of subdivision can promote coexistence of otherwise unstably interacting species. The present study offers a unique opportunity to investigate how habitat subdivision influences the structure and persistence of species assemblages. This work will be conducted in aquatic microcosms containing an assemblage of protozoans in which the pair-wise and multispecies interactions are known. Two alternative hypotheses will be tested: (1) Increased subdivision always decreases the persistence of all species, with the poorest dispersers becoming extinct soonest, and (2) Subdivision promotes the persistence of some or all species, at least up to some intermediate degree of subdivision; this would imply that interactions between species are important. These hypotheses will be tested by measuring the persistence of a variety of species combinations in microcosms with different degrees of subdivision. Dispersal rates will also be measured, so that the sequence in which species go extinct can be recorded. The experiments will show whether the response of assemblages to habitat subdivision can be predicted from the dynamics of the particular species involved, versus the type and details of between-species interactions. This study will demonstrate whether habitat fragmentation (subdivision) promotes biodiversity. In particular, the experiments will test the parts of ecological theory that are most directly relevant to predicting the response of endangered species living in patchy habitats to varying degrees of fragmentation.