2005 BES Annual Meeting Presentation and Poster Abstracts
Phytogeographic distribution of the invasive perennial weed mugwort (Artemisia vulgaris L.)
Abstract: One of the defining characteristics of an invasive species is anthropogenic introduction of propagules into novel habitats, often at great distances from their source. Despite the sizable human role in distributing non-indigenous species, we still know strikingly little about the mechanisms of successful establishment and future range expansion. What mechanism(s) allow invasive species to expand their range so rapidly? Can we find answers to this and correlated questions by examining the historical record? This study modeled the historical distribution of the invasive perennial weed mugwort (Artemisia vulgaris) in North America as a function of various abiotic (elevation, precipitation) and anthropogenic factors (population density) and location (latitude and longitude) at the scale of political units (US counties and Canadian municipalities). Herbarium records from 273 institutions were parsed into decadal increments and integrated into a geographic information system (GIS) as presence/absence. Join count analysis revealed that the current mugwort distribution is best described as secondary spread from founder populations across North America. The predictors with the most explanatory power were the area of the political unit and the population density of that unit. This logistic model was used to estimate the probability of supporting a mugwort invasion for each political unit, with the likelihood of mugwort invasion increasing 600% for every 10-fold increase in population density.