Figure 3.

Flowchart summarizing procedure for estimating influences of ecological processes, broken into two major steps discussed in the section ‘Estimating influences of ecological processes.' First, the observed degree of phylogenetic turnover for each pairwise community comparison was quantified (βMNTD_obs). A randomization was then used to generate a null distribution of phylogenetic turnover (βMNTD_null). The value of βNTI characterizes the magnitude of deviation between βMNTD_obs and βMNTD_null. The fraction of pairwise comparisons with significant βNTI values (|βNTI|>2) is the estimated influence of Selection. As part of the second major step in our procedure, pairwise comparisons with nonsignificant βNTI values were further evaluated by comparing observed Bray–Curtis (BC_obs) to Bray–Curtis expected under the randomization (BC_null). The value of Bray–Curtis-based Raup–Crick (RC_bray) characterizes the magnitude of deviation between BC_obs and BC_null; a value of |RC_bray|>0.95 was considered significant. The number of pairwise comparisons with RC_bray>+0.95, the number with RC_bray<−0.95 and the number with |RC_bray|<0.95 were each divided by the total number of all pairwise comparisons; the resulting fractions estimate the influence of Dispersal Limitation combined with Drift, Homogenizing Dispersal and Drift acting alone, respectively.