Data from: Dispersal enhances beta diversity in nectar microbes

Dispersal is considered a key driver of beta diversity, the variation in species composition among local communities, but empirical tests remain limited. We manipulated dispersal of nectar-inhabiting bacteria and yeasts via flower-visiting animals to examine how dispersal influenced microbial beta diversity among flowers. Contrary to the prevailing view that dispersal lowers beta diversity, we found beta diversity was highest when dispersal was least limited. Our analysis suggested that this unexpected pattern might have resulted from stronger priority effects under increased dispersal. Dispersal is highly stochastic, generating variability in species arrival history and consequently the potential for community divergence via priority effects, in these and likely many other microbial, plant, and animal communities. Yet most previous experiments eliminated this possibility. We suggest that the positive effects of dispersal on beta diversity, like the one we report here, may have been greatly underappreciated.扩散被认为是β多样性（beta diversity）——即局地群落间物种组成的变异——的关键驱动因子，但相关的实证检验仍较为有限。我们通过访花动物操控了栖息于花蜜中的细菌与酵母菌的扩散过程，以探究扩散如何影响花朵间的微生物β多样性。与“扩散会降低β多样性”这一主流观点相悖，我们发现当扩散受限程度最低时，β多样性反而最高。我们的分析表明，这一出乎意料的模式或许源于扩散增强时出现的更强优先效应（priority effects）。在本研究涉及的这类群落，以及诸多其他微生物、植物与动物群落中，扩散具有高度随机性，会造成物种到达历史的差异，进而产生通过优先效应引发群落分化的潜力。然而绝大多数既往实验都排除了这种可能性。我们认为，正如本研究报道的这一案例，扩散对β多样性的正向效应或许长期以来都被大大低估了。