Using Key Functional Traits to Explain Variation in Rates of Spread Among Invasive Plants in North America

Abstract

Invasive plants are major drivers of global change, capable of severely impacting the ecosystems they invade. Consequently, a major aim in invasion ecology has been to understand the dynamics of plant invasions and identify key determinants of spread. One factor hypothesized to explain interspecific variation in rates of invasion are functional traits. Intuitively, species with traits suited to colonization, dispersal, and rapid growth are predicted to spread faster. Despite this, empirical results surrounding the relationship between traits and various aspects of invasiveness remain mixed. Moreover, there is a dearth of research on the influence traits directly have on the rate of spread of a species across a range. To test this relationship, I reconstructed the invasion history of 247 vascular plant species invasive to North America in climate and geographic space. I then tested how well three functional traits (seed dry mass, plant height, and specific leaf area) could be used to predict various metrics of spread rate across these spaces. Of my tested traits, only plant height statistically explained variation in spread rate. However, both native range size and native niche breadth, covariates in my models, showed some predictive value. My results suggest that, when data are aggregated at the continental scale, functional traits are limited estimators of spread rate among invasive plants.