Propagule Pressure and Climate Contribute to the Displacement of Linepithema humile by Pachycondyla chinensis

Abstract

Identifying mechanisms governing the establishment and spread of invasive species is a fundamental challenge in invasion biology. Because species invasions are frequently observed only after the species presents an environmental threat, research identifying the contributing agents to dispersal and subsequent spread are confined to retrograde observations. Here, we use a combination of seasonal surveys and experimental approaches to test the relative importance of behavioral and abiotic factors in determining the local co-occurrence of two invasive ant species, the established Argentine ant (Linepithema humile Mayr) and the newly invasive Asian needle ant (Pachycondyla chinensis Emery). We show that the broader climatic envelope of P. chinensis enables it to establish earlier in the year than L. humile. We also demonstrate that increased P. chinensis propagule pressure during periods of L. humile scarcity contributes to successful P. chinensis early season establishment. Furthermore, we show that, although L. humile is the numerically superior and behaviorally dominant species at baits, P. chinensis is currently displacing L. humile across the invaded landscape. By identifying the features promoting the displacement of one invasive ant by another we can better understand both early determinants in the invasion process and factors limiting colony expansion and survival.

High diversity in an urban habitat: are some animal assemblages resilient to long-term anthropogenic change?

“…Another invasive species, P. chinensis, while present in 1979 was rare, recorded in just one sample. This species is now very common and the comparison of our study and that of Nuhn and Wright (1979) benchmarks the timeline of its spread, which more recent studies (Guénard and Dunn 2010;Rice and Silverman 2013), suggest can be rapid. A-priori we predicted based on McIntyre (2000) that the number of introduced species would increase through time.…”

Discovery–dominance trade‐off among widespread invasive ant species

“…However, the current distribution of highly invasive ants seems exclusive so far, at least at a local scale (LeBrun et al. 2007; Krushelnycky and Gillespie 2010; Spicer Rice and Silverman 2013). A possibility is that no ultimate “top invasive” ant species exists.…”

“…2012). For example, L. humile is superior at interference competition in the laboratory, but is nonetheless displaced by P. chinensis in areas where the climatic suitability is low for L. humile and high for P. chinensis (Spicer Rice and Silverman 2013). The results are contingent on the environmental conditions, while laboratory temperature, humidity, and diet are not necessarily representative of natural conditions (a limitation shared by many laboratory-based studies).…”

Climate Change May Boost the Invasion of the Asian Needle Ant

“…Consequently, invasion risk was exacerbated globally with entirely new areas covering large amounts of landmass becoming suitable. Given the important ecological impacts of P. chinensis [35] and its ability to potentially even displace one of the most aggressive and dominant species of invasive ants, the L. humile [81], clearly it is important that surveillance efforts of this species are increased to prevent further spread and aid early detection. Eradication of well established large invasive ant populations can be extremely challenging [32] if not impossible, but early detection of small incipient populations can enable managers to carry out early responses and achieve eradication [34].…”