Table 2.
Distribution parameters of pairwise taxonomic similarity among river basins in the six biogeographical realms and at the world scale for the historical and current situations
| Median, % | Skewness | Kurtosis | ||
| Afrotropical | Historical | 0 | 3.31 | 14.8 |
| Current | 0 | 2.89 | 10.0 | |
| Australian | Historical | 0 | 3.11 | 10.3 |
| Current | 0 | 2.96 | 9.7 | |
| Nearctic | Historical | 1.32 | 2.64 | 8.1 |
| Current | 3.88 | 2.46 | 7.4 | |
| Neotropical | Historical | 0 | 4.55 | 26.8 |
| Current | 0.16 | 4.19 | 22.1 | |
| Oriental | Historical | 0 | 4.06 | 17.7 |
| Current | 0 | 1.00 | 17.4 | |
| Palearctic | Historical | 2.04 | 2.75 | 8.6 |
| Current | 3.03 | 2.55 | 7.4 | |
| World | Historical | 0 | 6.35 | 50.4 |
| Current | 0 | 5.68 | 42.0 |
The historical situation indicates assemblages before introductions and extirpations attributable to human activities and corresponds to the preindustrial period. The current situation indicates today’s assemblages (native species − extirpated species + nonnative species).