LTREB Collaborative Proposal: Large-scale removal of introduced ants as a test of community reassembly

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The introduction of non-native species into ecosystems is a pervasive form of environmental change with negative impacts ranging from shifts in the number and types of species, compromised ecosystem services and, in some cases, extinction of native species. Surprisingly little information exists, however, regarding the capacity of ecological systems to recover after introduced species removal. In particular, only a handful of studies on species invasions combine long-term, pre-invasion data with invader-removal experiments over temporal scales long enough to determine whether or not native species assemblages fully recover. This project will examine the reassembly of native ant communities following the landscape-scale removal of the Argentine ant, a common, widespread and ecologically disruptive introduced species. Following invader removal, researchers will quantify recovery of native ant assemblages with respect to their genetic diversity, species diversity, and ecological function. Multiple approaches, such as those to be employed here, are required to further clarify the rate and extent to which ecosystems recover from this type of environmental change. Broader impacts related to this work include research support for PhD students from UC San Diego and UC Berkeley, a research experience for undergraduates program for students from California State University, Channel Islands (a four-year Hispanic Serving Institution), and a high school outreach program focused on understanding ecological effects of invasive species. The experimental removal of numerically dominant, introduced species can provide unparalleled opportunities to examine community reassembly. Invader-removal experiments can shed light on how reassembly is influenced by processes acting within a given system or, alternatively, reflects processes acting at larger spatial scales. The objectives of this research are to quantify the structural (genetic diversity, species diversity) and functional (trophic position, ecological function) components of the recovery of native ant assemblages following landscape-scale removal of the non-native Argentine ant. With large-scale eradication treatments on Santa Cruz Island, California, now complete, the project from this point forward will quantify native ant reassembly over a decadal time scale. The central hypothesis is that native assemblages will recover from invader removal but only if reassembly is measured over temporal scales (1) that are commensurate with the life history of focal native species, and (2) that encompass how interspecific interactions change during assemblage formation. This research will provide an unprecedented test of the capacity for native assemblages to regain structure and function after invader removal and also yield novel information about the factors that control the richness, composition and ecological function of an important terrestrial animal assemblage.