Data from: Measuring ectomycorrhizal fungal dispersal: macroecological patterns driven by microscopic propagules

Dispersal plays a prominent role in most conceptual models of community assembly. However, direct measurement of dispersal across a whole community is difficult at ecologically relevant spatial scales. For cryptic organisms, such as fungi and bacteria, the scale and importance of dispersal limitation has become a major point of debate. We use an experimental island biogeographic approach to measure the effects of dispersal limitation on the ecological dynamics of an important group of plant symbionts, ectomycorrhizal fungi. We manipulated the isolation of uncolonized host seedlings across a natural landscape and used a range of molecular techniques to measure dispersal rates of ectomycorrhizal propagules and host colonization. Some species were prolific dispersers, producing annual spore loads on the order of trillions of spores per km2. However, fungal propagules reaching host seedlings decreased rapidly with increasing distance from potential spore sources, causing a concomitant reduction in ectomycorrhizal species richness, host colonization, and host biomass. There were also strong differences in dispersal ability across species, which correlated well with the predictable composition of ectomycorrhizal communities associated with establishing pine forest. The use of molecular tools to measure whole community dispersal provides a direct confirmation for a key mechanism underlying island biogeography theory and has the potential to make microbial systems a model for understanding the role of dispersal in ecological theory.

扩散在绝大多数群落组装的概念模型中均占据核心地位。然而，在具有生态学意义的空间尺度下，对整个群落的扩散过程进行直接测量极具挑战。对于真菌、细菌这类隐存生物而言，扩散限制的尺度与重要性长期以来都是学界争论的核心议题。本研究采用实验性岛屿生物地理学方法，探究扩散限制对一类重要植物共生伙伴——外生菌根真菌（ectomycorrhizal fungi）的生态动态的影响。我们在自然景观中调控未定殖宿主幼苗的隔离程度，并结合多种分子技术测量外生菌根繁殖体的扩散速率与宿主定殖情况。部分物种具备极强的扩散能力，每平方公里每年可产生高达万亿级的孢子负荷。但随着潜在孢子源距离的增加，抵达宿主幼苗的真菌繁殖体数量会快速减少，进而导致外生菌根物种丰富度、宿主定殖率与宿主生物量同步下降。不同物种间的扩散能力也存在显著差异，这与在建松林中形成的外生菌根群落的可预测组成高度匹配。借助分子工具实现全群落扩散过程的直接测量，为岛屿生物地理学理论的核心机制提供了直接实证支持，同时也有望将微生物系统打造为探究扩散在生态学理论中作用的研究模型。