Reference # 6454635

TOPIC 8. Plant invasions

East Asian plants in Eastern US forests: are invaders pre-adapted for more efficient resource use?

Syracuse University, Syracuse, New York, USA

The globalization of human activities has resulted in the widespread movement of plants around the world. Paradoxically, many of these exotic species are out-competing native plants, despite the presumption that native species have locally adapted to their environments. Further, global invasion patterns are frequently asymmetric, with some regions more likely to produce invasive species and others more likely to be invaded. This phenomenon is particularly prominent in eastern North American (ENA) forests, where an unexpected, substantial fraction of woody invaders originated from East Asia (EAS). Although both regions lie primarily in the north temperate mesic forest biome with comparable niches, EAS has much greater phylogenetic and species diversity than ENA. Historically, diversity differences may have led to greater competition and intense selection for more efficient resource-use strategies in the EAS flora. This bias could provide a mechanistic explanation for modern invasion patterns between the floristic regions. We used a large database of leaf physiological traits (including photosynthetic rate, leaf lifespan, leaf mass per area, and leaf nitrogen) and species native distribution data to test for large-scale functional differences among biogeographic regions. With some exceptions, the EAS flora exhibited a generally more efficient carbon economy than ENA plants. This general finding was supported in a common garden study that compared the leaf physiologies of congeneric ENA native and EAS invasive shrubs and lianas. These included 31 species representing 6 plant families from 8 genera, including Lonicera, Euonymus, Berberis, Celastrus, and Rhamnus. On average, introduced EAS species invasive in ENA forests had similar leaf metabolic costs, but had greater photosynthetic returns than ENA natives. Efficiency differences were further magnified through time when considering leaf lifespan. Overall, these findings suggest important region-level functional differences between ENA and EAS floras and could have implications for understanding modern patterns of floristic interchange and community re-assembly through plant invasions.

© 2012 Organizing Committee