PARENT SESSION
Oral Session # 60: Invasive Species V: Genetics; Chemical Cycling Effects.
Presiding: S Miao
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.

Genetic sampling of emigrants affects plant height and vigor in new ranges.

Kinter, Cecilia^*,1, Mack, Richard¹, ¹ Washington State University, Pullman, WA

ABSTRACT- For two centuries, the tallest, most vigorous members of plant species have often been reported in new, rather than native, geographic ranges of the species. Attempts to evaluate whether these observations underlie a generalization about the performance of alien plants have produced equivocal results. Where differences have been documented, they have been attributed to environmental factors in the new range: greater resource availability, or release from competition, predation, grazing, or parasitism, or to post-introduction evolution. Several hypotheses have been proposed, including Enemy Release, Environmental Constraint, Historic Herbivore Pressure, Optimal Defense, and Evolution of Increased Competitive Ability. None of these hypotheses has provided a comprehensive explanation for the varied performance of alien plants. Alternatively, we asked whether the geographic source of immigrant populations affects subsequent performance by comparing height and vigor of the annual grass Bromus tectorum L. (cheatgrass, downy brome) from native European populations, highly invasive North America populations, and New Zealand populations which are naturalized, but not invasive. In four common greenhouse experiments, North American plants typically were tallest and most vigorous, followed by European and lastly New Zealand plants (ANOVA, p < 0.05). These differences in performance cannot be attributed to environmental or maternal effects, and so must be due to heritable differences among plants from each region. Furthermore, these genetic differences are products of the different locales in the donor ranges from which emigrant populations were gathered. We found no evidence of the evolution of novel phenotypes. Phenotypic trait values for both sets of introduced plants form discrete subsets (Canonical Discriminant Function Analysis, p < 0.0002) of values for the native range. Our results hold implications for prediction of whether a species will become invasive in a new range, as well as for biosecurity, quarantine regulations, herbicide efficacy, biocontrol, and the conservation of biodiversity.

Key words: predicting invasions, Bromus tectorum, invasive species, founder effects