Figure 1.
Worldwide Distribution of Non-Native Freshwater Fish
(A) The percentage of non-native species per basin (i.e., the ratio of non-native species richness/total species richness) and (B) the non-native species richness per basin. Each basin was delimited by a GIS using 0.5° × 0.5° unit grid. The maps were drawn using species occurrence data for 9,968 species in 1,055 river basins covering more than 80% of continental areas worldwide. Invasion hotspots are defined as areas where more than a quarter of the species are non-native (red areas on map (A)), leading to define six invasion hotspots: the Pacific coast of North and Central America, southern South America, western and southern Europe, central Eurasia, South Africa and Madagascar, southern Australia, and New Zealand.
Figure 2.
Percentage of Threatened Species for the Three Invasion Levels
Threatened species were identified from the IUCN Red List (vulnerable, endangered, critically endangered). We calculated the percentage of threatened species, listed in the IUCN Red List, for the three invasion levels considered in Figure 1A. Each invasion level expessed as the percentage of non-native species. ([ 0%–5% ], ]5%–25%], ]25%–95%]) account for 8,363, 2,257, 1,241 native species and 544, 240, 271 river basins, respectively.
Table 1.
Spearman Rank Correlation (rs) between the Number of Non-Native Fish Species (Residuals) and Each Explanatory Variable Related to the “Human Activity,” “Biotic Acceptance,” and “Biotic Resistance” Hypotheses (n = 597)
Table 2.
Independent Effect of Each Environmental and Human Activity–Related Variable on the Number of Non-Native Species per Basin