On a level field: The utility of studying exotic and native species in successional systems

Biological invasions are of critical interest as invaders are both model ecological systems and serious management concerns.  A fundamental, and unresolved, question in invasion biology is whether successful exotic species inherently differ from successful natives.  Successional areas are useful model systems as they place all plant species in the role of invader, avoiding the bias associated with comparing established resident native species with establishing populations of exotics.  As ecological restoration often involves the manipulation of successional processes, accurate estimates of invasion dynamics are necessary to determine management strategies and priorities.  We used data from a long-term, permanent plot study of old field succession (the Buell-Small Succession Study) to compare the dynamics and characteristics of native and exotic species.  Overall, native and exotic plants did not systematically differ with both groups exhibiting similar population dynamics during succession.  Even the most invasive species at the site were not distinguishable from similar native taxa.  In contrast to nativity, life form was a consistent and strong determinant of population dynamics.  The traits of species present in the study were also compared between native and exotic taxa.  This analysis also revealed few differences among native and exotic taxa.  While individual exotic species may behave differently than ecologically similar native species, successful exotic species as a whole cannot be separated from the range seen within native taxa.  In contrast, relatively simple life-history groupings can explain much of the variation among species, and be used to generate management recommendations.