Invaders are not a random selection of species

KARATAYEV, ALEXANDER; BURLAKOVA, LYUBOV; PADILLA DIANNA; OLJENIN, SERGEJ; BOLTOVSKOY, DEMETRIO

Nijmegen, Netherlands

Congreso; ICAIS 2007 (15th International Conference on Aquatic Invasive Species); 2007

ICAIS

We examined the distribution of freshwater exotic invertebrates in Europe and North America across a wide range of taxa, feeding habits and tolerance to organic pollution. A database with information on species that are known to be invaders in Europe or invaders elsewhere but of European origin (75 species) and invaders in North America or invaders elsewhere but of North American origin (65 species) was analyzed and compared with the native species richness on both continents. 1) The distribution of exotic species across taxa was not random. Crustacean and molluscan invaders dominated on both continents, and comprised 72% of all aquatic exotic invertebrate species in Europe and 86% in North America. In contrast, crustaceans and molluscs together formed only 11% of the biodiversity of all native freshwater invertebrates in North America (22,183 species total) and 18% in Europe (11,613 species total). 2) Although aquatic insects are the most diverse group on both continents, numbers of invasive species among insects was disproportionally low. 3) Many native species (35.5%) are intolerant of significant amounts of organic pollution (using the rating scale developed by Hilsenhoff and used by the US EPA). In contrast, all exotic species are tolerant to significant amounts of organic pollution. However, similar to non-invaders (3.8% of 880), less than 3% of 105 exotic species can tolerate severe organic pollution. 4) The distribution of species among feeding groups is also different for exotic species than for native species. Suspension feeders are disproportionally more abundant and predators are less abundant among exotic species than among native invertebrates. Therefore, the ongoing spread of exotic species affects the biodiversity of selected taxa, shifts communities toward greater tolerance to organic pollution and increases the numbers of suspension feeders, thereby enhancing benthic pelagic coupling in waterbodies with high densities of invaders. Because these processes are very similar in Europe and North America, we suggest that the observed patterns may have a common global effect.