As local communities within a metacommunity may differ considerably in their contributions to biodiversity and ecosystem functioning, it has been suggested that conservation priority should be given to disproportionately important local communities (i.e., keystone communities). However, we know little about what characterizes a keystone community. Using laboratory protist microcosms as the model system, we examined how the environmental uniqueness and location of a local community affect its contributions to the metacommunities. We found that the removal of local communities with unique environmental conditions, which supported endemic species, reduced regional-scale diversity, qualifying them as regional-scale keystone communities. In addition, the local communities possessing unique environmental conditions had greater impacts on ecosystem functions, including biovolume production and particulate organic matter decomposition. We also found that keystone communities for biovolume production were not keystone for organic matter decomposition, and vice versa. Our study, therefore, demonstrates the important role of keystone communities in maintaining biodiversity and functioning of metacommunities.

由于一个元社区内的地方社区对生物多样性和生态系统功能的贡献可能存在很大差异，因此建议将保护重点放在不相称的重要地方社区（即基石社区）上。但是，我们对基石社区的特征知之甚少。使用实验室的原生生物缩微作为模型系统，我们研究了环境的独特性和当地社区的位置如何影响其对超社区的贡献。我们发现，去除具有独特环境条件的地方社区，这些地方条件支持地方特有物种，减少了区域尺度的多样性，使他们成为区域尺度的基石社区。此外，具有独特环境条件的当地社区对生态系统功能（包括生物量生产和颗粒有机物分解）的影响更大。我们还发现，生物量生产的关键族群不是有机物分解的关键族群，反之亦然。因此，我们的研究证明了基石社区在维护生物多样性和元社区功能方面的重要作用。