THE TAXONOMIC DISTRIBUTION OF INVASIVE ANGIOSPERM PLANTS - ECOLOGICALINSIGHTS AND COMPARISON TO AGRICULTURAL WEEDS

Global data sets of serious agricultural weeds (1348 species), widespr ead agricultural weeds (1041 species), and threatening natural area in vaders (381 species) were assembled, and taxonomic patterns among thes e data sets were compared to gain insights into how these groups diffe r ecologically. Angiosperm taxonomic groups (families, orders and subc lasses) were tested for over-and under-representation using resampling tests, and ecological characteristics of plant families were correlat ed with the prominence of each family ill the data sets. As predicted by Baker's previously proposed attributes of 'ideal' weeds, many over- represented families among agricultural weeds contained primarily herb aceous, rapidly reproducing, abiotically dispersed species. The natura l area invaders, in contrast, were represented by a more ecologically diverse range of families and were over-represented by more largely wo ody families. Families with at least some abiotically pollinated speci es averaged significantly higher proportions of natural area invaders (p=0.001) and agricultural weeds (p < 0.001) than biotically pollinate d families. Families containing climbing species were more highly repr esented among natural area invaders than families without climbers (p< 0.009). While all nonnative plants may carry some risk of becoming nat ural area invaders, this taxonomic analysis suggests that plants with amongst the highest risk of becoming natural area invaders worldwide i nclude: species that are primarily aquatic or semi-aquatic, grasses, n itrogen-fixers, climbers, and clonal trees. Only 25% of natural area i nvaders were serious agricultural weeds, so quarantine legislation aim ed at curbing the introduction of nerv agricultural weeds will be unli kely to prevent the introduction of most natural area invaders. (C) 19 98 Elsevier Science Ltd. All rights reserved.