There is some evidence that species traits, especially in plants, may be useful for predicting invasiveness. My dissertation on the Commelinaceae (dayflower family) suggests that there are some traits that may usefully predict invasiveness in this family, including self-compatibility, annual life history, the presence of vegetative reproduction, and (marginally) the presence of seed heteromorphism, which are all associated with the invaders. High levels of autogamous selfing, and (marginally) high specific leaf area (thin leaves) are also associated with these invasive species (Burns 2006, unpublished dissertation).
Knowing something about the response of traits to environment also seems to be an important key to predicting invasion successfully. Experiments with five pairs of invasive and noninvasive congeners suggest that some traits successfully predict invasiveness, but only when they are measured in certain environments. Such traits include specific leaf area and root to shoot ratio (Burns 2006). This suggests to me that experiments (maybe in a greenhouse) that measure traits across environments (e.g. different nutrient availabilities) may improve our ability to detect invasiveness. Traits from the literature may be insufficient to predict invasiveness (especially if the environment differs between native and introduced ranges).
Demographic models based on these same experiments also suggest that these invasive species exhibit opportunistic responses to high nutrient availabilities, but are similar to noninvasive species when nutrient availabilities are low (in performance measures such as fecundity and vegetative reproduction). The noninvasive species all had very low levels of performance plasticity (not adaptive plasticity). This suggests a possible way of identifying noninvasive species by their low levels of performance plasticity (Burns 2006, unpublished dissertation).
Propagule pressure was also a significant predictor of invasiveness, so introduction history does matter. |