Selected life-history traits are frequently associated with persistent nonindigenous species and may be useful in predicting or assessing the likelihood of establishment of a given species. However, many exceptions occur for any given trait, and most can be evaluated only subjectively or qualitatively. Quantitative comparisons between the traits of species that have become established and the traits of species that have failed to establish are rare, especially for arthropods and pathogens. Nevertheless, there are traits that appear to enhance establishment, and these require much further study.
The ability to change from outcrossing to selfing in response to local environmental conditions could optimize the opportunity for establishment. Species with high phenotypic plasticity among many ecologically important traits (for example, the traits collectively considered in connection with phenology) also have an advantage in a new environment. Possession of a resistant dormant phase, particularly a resistant seed bank, appears important, as do alternative forms of asexual and sexual reproduction, rapid growth, and high fecundity.
Nonindigenous plant pathogens with genetic variability in traits associated with reproduction have a higher probability of establishment. Traits of plant pathogens that appear to enhance establishment include a short infection cycle, high productivity of infectious units, and a long infectious period.
High intrinsic rate of increase, uniparental reproduction, and a dormant or resilient life stage that permits surviving temporally unfavorable conditions characterize many insect invaders. Other life-history strategies, such as long-lived adult stages, are common among established nonindigenous insects.