The Role of the Number of Phylogenies on Site Scores
In our dataset the number of phylogenies with species occurring at a site ranged between 5 and 16 (mean and median = 11). So, the first point that we investigated was the role of the number of phylogenies in site's scores. This showed that over 75 % of the site's ranking with Ws sum was explained by the number of phylogenies with species in the site (Regression model: Sum Ws = −2.13 + 0.555 number of phylogenies; F = 41.75; DF = 14; p = 0.000; R2 = 0.75). With Ws ranks the influence of the number of phylogenies is a bit smaller but still important (Regression model:
Ws ranks = −1.03 + 0.259 number of phylogenies; F = 26.75; DF = 14; p = 0.000; R2 = 0.66).
Based on it, we decided to standardize by dividing total Ws sum or total Ws ranks in the site by the number of phylogeny occurring in it. As expected, this came to a result where much less of the site's ranking is explained by the number the phylogenies with species occurring in the site, but the number of phylogenies still explains a substantial proportion of the variance (Regression model: Ws sum/number of phylogenies = 0.04 + 0.0105 number of phylogenies; F = 8.9; DF = 14; p = 0.01; R2 = 0.39; and Ws ranks/ number of phylogenies = 0.082 + 0.0237 number of phylogenies; F = 6.29; DF = 14; p = 0.025; R2 = 0.31). In both cases, the standardized and nonstandardized values are still correlated (Spearman r = 0.9, p <0.01; and r = 0.83, p < 0.01 for Ws sum and Ws ranks, respectively). But ranking priorities change, putting in evidence the phylogenetic distinctiveness of some groups occurring in sites with less phylogeny (Figs. 2 and 3).
The Influence of Species Richness on Site Scores
The number of species in the 16 sites varied between 10 and 68 (mean = 33; median = 31), and over 80 % of variation in the sum of Ws is explained by species richness. When Ws sums are standardized by the number of phylogenies, 70 % of the variation is still explained by species richness – sites with more species have greater chances of accumulating high Ws sums (Fig. 4a, b).
The analysis with Ws ranks shows that all sites had at least one top or second ranking species (1–14 per site, mean and median = 7). The influence of species richness on Ws ranks is lower than Ws sums with just over 50 % of the variation in Ws ranks explained by species richness. When Ws ranks were standardized by the number of phylogenies, the influence of species richness became much lower (32 %), although still significant (Fig. 5a, b).