Beta diversity measures for the rare biosphere sub-groups across the 4 quadrants compared to the total rare biosphere (n≤5).

aNUNN are the non-unique non-novel members, UN are the unique novel members, UNN are the unique non-novel members, total correspond to the total rare biosphere defined at the empirical cutoff of n≤5.
bNumbers are averages ± standard deviations of shared/unshared OTUs percentages for 4 data points (1 quad, and 3 quads) and 6 data points (2 quads). The percentages were calculated by dividing the number of shared/unshared OTUs between “x” quadrants by the total number of observed OTUs in those “x” quadrants. The number of shared OTUs between 2 quadrants also includes the number of OTUs that these 2 quadrants share with either one or two more quadrants. The number of shared OTUs between 3 quadrants also includes the number of OTUs that these 3 quadrants share with the fourth quadrant.
cAll similarity indices values are averages ± standard deviations of 6 pair wise comparisons. We only chose those similarity indices that use the relative abundance data (instead of the abundance or the presence-absence data) due to the difference in sample sizes of the 4 groups compared.

a aNUN代表非唯一非新颖成员，UN代表唯一新颖成员，UNN代表唯一非新颖成员；三者之和对应的总集合，即为以经验阈值n≤5界定的总稀有生物圈（total rare biosphere）。
b 数值为4组数据点（对应1个样方与3个样方的场景）以及6组数据点（对应2个样方的场景）的共享/非共享操作分类单元（Operational Taxonomic Unit，OTU）占比的平均值±标准差。该占比通过将“x”个样方间的共享/非共享OTU数量，除以这些“x”个样方中观测到的OTU总数量计算得到。两个样方间的共享OTU数量，同时包含这两个样方与另外1个或2个样方共享的OTU；三个样方间的共享OTU数量，同时包含这三个样方与第四个样方共享的OTU。
c 所有相似性指数值均为6组两两比较结果的平均值±标准差。由于本次对比的4组样本量存在差异，我们仅选用基于相对丰度数据（而非绝对丰度或有无数据）计算的相似性指数。