Number of singleton clusters (σ), total number of clusters (Σ), and maximum cluster size (max) for TreeCluster and GreenGenes for various thresholds.

In the Greengenes database, OTU definitions for thresholds α = 0.015 and α = 0.045 are not available.在Greengenes数据库中，针对阈值α=0.015与α=0.045的操作分类单元（Operational Taxonomic Unit，OTU）定义暂未提供。