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（dispersal）在绝大多数群落构建的概念模型中都占据核心地位。然而，在生态学相关的空间尺度下，直接测定整个群落的扩散情况极具挑战。对于真菌、细菌这类隐栖生物（cryptic organisms）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（experimental island biogeographic approach），探究扩散限制对一类重要植物共生体——外生菌根真菌（ectomycorrhizal fungi）生态动态的影响。我们在自然景观中操控未定植宿主幼苗的隔离程度，并借助一系列分子技术测定外生菌根真菌繁殖体的扩散速率与宿主定植情况。部分物种为高效扩散类群，其年孢子负荷可达每平方公里万亿级别的孢子量。然而，抵达宿主幼苗的真菌繁殖体数量会随着其与潜在孢子源的距离增加而快速下降，进而导致外生菌根真菌物种丰富度、宿主定植率与宿主生物量同步降低。不同物种间的扩散能力亦存在显著分化，这与发育中松林关联的外生菌根群落的可预测组成高度匹配。借助分子工具测定整个群落的扩散情况，直接验证了岛屿生物地理学理论（island biogeography theory）背后的核心机制，同时也为将微生物系统作为解析扩散在生态学理论中作用的研究模型提供了潜在可能。