| "New" plant species continue to be introduced to North America for horticultural and agricultural purposes and it is probable that some will escape cultivation and become invasive in native ecosystems. Little is known about the biology of invasive species and, in particular, why some species are invasive while others are not. This dissertation presents a retrospective analysis of the characteristics of woody plants introduced to North America in order to determine if invaders have characteristics that distinguish them from introduced plants which do not invade and to determine whether these characteristics can be used to predict invasive potential.; The 235 woody plant species that invade in North America differed significantly in several characters from 114 species that do not invade. Those characters included vegetative reproduction, length of the juvenile period, length of flowering and fruiting times, seed germination requirements, and area of origin. Whether or not a species invades elsewhere in the world differed between the two groups of species. Predictive models derived from discriminant analysis (DA) and classification and regression trees (CART) were created using a portion of the species and tested on the remaining species. The DA model correctly classified 86.2% of the species in cross-validation, while the CART model classified 76% correctly, in both cases using combinations of the characters previously mentioned. From these analyses a hierarchical predictive tree, the "synthesis model," was created. This tree, when tested on the species in the study, admitted no successful invaders. Analyses by climatic region showed that essentially the same characters contributed to invasive success throughout North America and the regional predictive models had approximately the same level of accuracy, as did the overall synthesis model.; The successful invaders were in 125 genera, with only eight genera having more than four invasive species. Twenty-eight of the 125 genera also had species among unsuccessful invaders. Of the 53 families represented among the successful invaders, seven, or 13%, contributed two-thirds of the species considered to be "pest" species. Thus, while taxonomic affiliation cannot be used to predict invasive potential, species in these families could be considered a high risk. |
