Fig. 4. Community assembly processes of abundant and rare taxa. (a) Patterns of the beta nearest taxon index (βNTI) for the abundant and rare taxa. The horizontal dashed lines represent upper and lower significance thresholds at βNTI = +2 and -2, respectively. (b) Depiction of the contribution of the ecological processes that determine community assembly of the abundant and rare taxa. Heterogeneous selection (HeS), homogeneous selection (HoS), dispersal limitation (DL), homogenizing dispersal (HD), and Undominated.