Research :: Ecology of Invasive Species
Summary
Invasive plants represent a major threat to the economy and the environment of the United States. For example, it was estimated that the economic costs of weeds in agricultural systems totaled $20 billion in 1994. More generally, Pimentel et al. (1999) suggested that invasive, non-indigenous species (plants, animals and microbes) cause damages and losses in the United States worth more than $138 billion per year. Separate from direct economic costs, weedy and invasive species in parks, refuges, preserves and natural areas threaten biodiversity and the functioning of ecosystems, rivaling habitat loss in their destructive effect. Invasive species can also alter physical features of their environment such as disturbance regime, hydrology and soil chemistry.
A major research focus in our lab is on how microbial interactions affect the ecology of invasive species. In addition to work with tall fescue and black cherry described elsewhere, we have been examining the ecological consequences of actinorhizal symbiosis between Frankia bacteria and autumn olive (Elaeagnus umbellata). Originally introduced as an ornamental and to reduce soil erosion, improve soil fertility and provide wildlife habitat and food, Autumn Olive has invaded a wide range of managed and native habitats in eastern North America. We are seeking to determine whether the population density and spatial distribution of Frankia limits Autumn Olive invasions, and whether this symbiosis can precipitate "invasional meltdowns" due to increased soil N levels. Preliminary data suggest that compatible Frankia populations, estimated by nodule formation on initially sterile AO, vary among past and present land uses, and local density of Autumn Olive.
Another research theme is to determine how hybridization between crops and weedy relatives affects the evolution of weediness. Past work with Susan Langevin (Grace) at LSU quantified rates of hybridization between cultivated rice and weedy red rice (both Oryza sativa). In collaboration with Loren Rieseberg and Ken Whitney, we examined the origin of weedy sunflowers (Helianthus spp.) via hybridization.
An ongoing project, with graduate student Luke Flory and post-doc Angie Shelton, is examining the invasion and spread of Microstegium vimineum (Japanese stiltgrass) in eastern deciduous forests and the impact of these invasions on forest regeneration. As part of this project we are: (1) characterizing invaded sites and monitoring the process of natural and experimental invasions; (2) determining the impacts of Microstegium invasion on tree regeneration and growth in natural and experimental systems; and (3) developing spatially-explicit predictive models for Microstegium invasions and forest impacts. This research is being supported by a grant from the U. S. Forest Service.
Representative Publications on the Ecology of Invasive Species (download PDF)
Representative Photos
