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Date Submitted

Fall 10-24-2013

Research Mentor and Department

Tiffany Knight

Restricted/Unrestricted

Dissertation/Thesis

Abstract

In an increasingly globalized world, invasive exotic species pose one of the greatest threats to native ecosystems. However, not all exotic species are invasive, which leads to a pressing question: what traits do certain exotic plants have that lead to invasiveness? One challenge that any potentially invasive species must face is competition with other plants in the community. As part of a larger study of invasive plants at the Tyson Research Center, we study the role of competition in reducing fitness of six invasive plant species. Then we assess the plant traits that allow these species to overcome competition with differing degrees of success. For each species, we compare the fitness of individuals in a competitor removal treatment and a control treatment. For the competitor removal treatment, we remove all competitors from in and around the plots, and measure the dry biomass of competitors removed from each plot. For each species, we expect the amount of removed biomass in the competitor removal treatment to correlate positively with an increase in fitness over the control group. However, many of our species are not strongly affected by the competitor removal treatment. To investigate why, we examine two plant traits: (1) allelopathy- the chemical inhibition of one plant by another, and (2) disturbance adaption. We use a literature search to assess allelopathy. Then we measure specific leaf area- the leaf area per dry mass unit, for our six invasive species compared to the local community and use it as a proxy for rapid growth and disturbance adaption. Our results suggest that there are multiple mechanisms that allow exotic plants to become invasive, and that more work is needed to understand trends in how exotics exploit these mechanisms.