The global wildlife trade is a major invasion pathway for plants and animals. Remarkably, invasive species are overrepresented in the ornamental plant trade relative to native species. However, the underlying cause of this pattern is unknown. There are two potential explanations. One hypothesis is that wildlife trade has dispersed many species in the past and provided opportunities for those species to establish outside of their native range and become invasive. Alternatively, invasive species could be overrepresented among traded species because biological characteristics favoring invasiveness may also increase their commercial success. Previous studies did not distinguish between these two explanations. To achieve this, we studied the emergent internet trade in ants as pets. Because this trade is extremely recent, it cannot be responsible for current invasions. First, we tested if non-native ants are overrepresented among traded species. Then, we tested if biological characteristics favoring invasiveness are also linked to commercial success, using eight morphological and life history traits previously found to be associated with invasiveness. Finally, we used this trait information to predict which other traded species are most likely to become invasive in the future.
Results/Conclusions
We recorded 521 ant species sold online. Among them, 98 species have established alien populations outside of their native range, including 13 out of the 19 ant species listed as invasive by the Invasive Species Specialist Group of the IUCN due to their high ecological and economic impacts. Alien and invasive species represent only two percent of the global species pool but 19 percent of traded species. Five traits were linked to both invasiveness and commercial success: habitat generalism, nesting generalism, association with disturbed habitats, colony size and worker polymorphism. This suggests that invasive species are overrepresented in the pet trade because biological characteristics favoring invasiveness also increase commercial success. Thus, the global wildlife trade does not simply transport a random subset of all native species but instead selects species with morphological and life history traits promoting invasiveness. Using this trait information, we estimated that 11% of traded native species are likely to become invasive in the future.