The role of opportunity in the unintentional introduction of nonnative ants

*[A longstanding goal in the study of biological invasions is to predict why some species are successful invaders, whereas others are not. To understand this process, detailed information is required concerning the pool of species that have the opportunity to become established. Here we develop an extensive database of ant species unintentionally transported to the continental United States and use these data to test how opportunity and species-level ecological attributes affect the probability of establishment. This database includes an amount of information on failed introductions that may be unparalleled for any group of unintentionally introduced insects. We found a high diversity of species, 232 species from 394 records, 12% of which have become established in the continental United States. The probability of establishment increased with the number of times a species was transported, propagule pressure, but was also influenced by nesting habit. Ground nesting species were more likely to become established compared with arboreal species.]