Experimental evidence that human impacts drive fire ant invasions and ecological change

Abstract

Biological invasions are often closely associated with human impacts and it is difficult to determine whether either or both are responsible for the negative impacts on native communities. Here, we show that human activity, not biological invasion, is the primary driver of negative effects on native communities and of the process of invasion itself. In a large-scale experiment, we combined additions of the exotic fire ant, Solenopsis invicta, with 2 disturbance treatments, mowing and plowing, in a fully crossed factorial design. Results indicate that plowing, in the absence of fire ants, greatly diminished total native ant abundance and diversity, whereas fire ants, even in the absence of disturbance, diminished some, but not all, native ant abundance and diversity. Transplanted fire ant colonies were favored by disturbance. In the absence of disturbance and on their own, fire ants do not invade the forest habitats of native ants. Our results demonstrate that fire ants are ''passengers'' rather than ''drivers'' of ecological change. We propose that fire ants may be representative of other invasive species that would be better described as disturbance specialists. Current pest management and conservation strategies should be reassessed to better account for the central role of human impacts in the process of biological invasion.community organization ͉ competition ͉ disturbance ͉ exotic species ͉ pest management

Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta

“…In spite of this shortcoming that cannot be overcome, the data here still provide convincing evidence that lack of pathogens frequently is associated with recent introductions of S. invicta. Such release from pathogens likely contributes to the invasion success of this ant, but other associated factors including human disturbance (King and Tschinkel 2008), superior competitive ability against local ants (Porter and Savignano 1990), and social form composition in the original founder population (Yang et al 2009) are also likely to be important.…”

Extreme life history plasticity and the evolution of invasive characteristics in a native ant

“…Studies involving introduced, invasive ants show that both factors may play a role. Human activity played a major role in biological invasions involving red imported fire ants, Solenopsis invicta, and habitat disturbance (King and Tschinkel 2008) or habitat preferences (Stuble et al 2009) rather than interspecific competition had the greatest impact on ant communities. In contrast, Argentine ants, Linepithema humile, appear adept at invading undisturbed, native habitats and are a primary driver of ecological change (Holway and Suarez 2006).…”

Experimental evidence for mediation of competition by habitat succession

“…For example, different species of red wood ant, Formica rufa group, are thought to structure assemblages at different stages of habitat succession (Punttila et al 1996) and competitively dominant native species may use the simple habitat of access roads to colonize national parks (Gibb and Hochuli 2003) or may be favored by fire (Parr and Andersen 2008). Invasive species, which are often behaviorally dominant, may be associated not only with species-poor native ant assemblages, but also with habitat disturbances (Bolger et al 2000, Menke et al 2007, King and Tschinkel 2008, suggesting that negative outcomes for native ant assemblages may result from synergies between disturbance and competition.…”