ECOPHYSIOLOGICAL TRAITS OF INVASIVE AND NON-INVASIVE INTRODUCED IMPATIENS SPECIES

Biomass allocation and leaf attributes are traits that discriminate between plants that exploit different light resource environments. Disturbed and high light environments provide easy access for resource-demanding, fast-growing invasive species. Comparing growth, ecophysiological and reproductive characteristics between invasives and non-invasives could help to predict a species' invasiveness and identify which habitat would be most susceptible to its invasion. In a common garden experiment we compared traits in Impatiens species that vary in their invasive status. They were the aggressive invader Impatiens glandulifera, which is invasive in mainland Europe and Ireland, I. parviflora, invasive in Central and Northern Europe but only established and not invasive in Ireland, and I. balfourii, naturalised in central and southern Europe but not reported in Ireland. We aimed to investigate their ecological requirements and to identify which traits promote invasion in this genus in a high-resource environment. Photosynthetic and allometric traits characterised the contrasting investment in light harvesting and carbon fixation of I. parviflora and I. glandulifera. The comparison of reproductive, photosynthetic and growth characteristics explained I. glandulifera's superior invasiveness when compared to I. parvilflora. However, there was no evidence that the invasive performed better than the non-invasive when it was compared to I. balfourii. Other traits that were not considered in this study, such as germination characteristics and adaptability, might also be responsible for invasiveness. We conclude that I. balfourii may possess an intrinsic invasiveness that, due to differences in invasion history, may not have reached its full potential yet.