Invasive Plants Have Scale-Dependent Effects on Diversity by Altering Species-Area Relationships

Abstract

The Scale of Plant Invasions Many studies have shown large effects of invasive species on native species diversity, but at the same time, invaders (especially plants) have rarely been implicated in the extinctions of native species. Powell et al. (p. 316 ) noted that studies showing large effects have tended to be focused on smaller spatial scales, while those showing smaller effects have usually been on broader spatial scales. For such a scale-dependent effect to occur, invasive species must alter the shape of the species-area relationship (SAR). Comparing the differences in SARs with invaded and uninvaded communities of plants in three different ecosystem types in the United States revealed smaller effects of invasive species on biodiversity at increasingly broader spatial scales. Empirical data and simulations suggested that the observed patterns result from disproportionately greater influences of invasive species on common relative to rare species that result from a combination of sampling effects and differential responses to invasion.