Assessment of the Argentine ant invasion management by means of manual removal of winter nests in mixed cork oak and pine forests

Abstract

The dynamic in Argentine ant colonies varies seasonally, influenced by biotic and abiotic factors. In winter the spatial range of the colony is contracted in large formations (winter nests) containing a large number of queens and workers. Winter nests are the clue to the species' dispersion power and the invasion of new habitats. For this reason a yearly elimination of queens and workers in winter at the edge (front) of the invasion could be a useful tool for weakening the species' dispersion and therefore limiting its establishment in new areas. Here, we determined the spatial dynamics of the Argentine ant nests during 1 year, and we assessed the invasion management by means of manual removal of winter nests for two consecutive winters, determining its effects during the following 3 years. We mapped nests found in 18 plots divided into two groups: extirpated (with removal of nests) and non-extirpated (control), along the fronts of three locations. Seasonal variation in the abundance of nests and workers, together with the two-year extirpation effects were evaluated. We found that colonies tended to follow an annual cycle of contraction and dispersion, with a decrease in the number of nests as we approached the invasion front. The extirpation was effective only in the front area, where it promoted smaller, less lasting and aggregated nests, as well as a decrease in the abundance of queens and workers. Nests also experienced a decrease during the two first winters but a recovery in the third, when no extirpation was done. Thus, a yearly perturbation should be performed to keep the expansion of the Argentine ant at a low rate, and to limit its establishment in new areasThis work was financed by the Spanish Ministry of Science and Innovation with the support of a predoctoral grant (BES-2008-005102) associated with research projects MEC/FEDER2007-64080-C02-02/BOS and CGL2010-16451, and a FI grant from the European Social Fund and the DIUE of the Autonomous Government of Catalonia in support of ML

Cuticular hydrocarbons correlate with queen reproductive status in native and invasive Argentine ants (Linepithema humile, Mayr)

“…It is a major invasive species, and in its non-native range, it is unicolonial—the population consists of nests without clear colony boundaries—and highly polygynous [ 8 , 9 ]. Its colonies are seasonally polydomous as a consequence of environmental conditions and food resource availability [ 10 , 11 ]. Moreover, its workers are completely sterile [ 12 ].…”

Behavioral responses to numerical differences when two invasive ants meet: the case of Lasius neglectus and Linepithema humile

“…The statistical results are at the top of each graph; they are in bold when significant. The boxplots show the median, upper and lower quartiles, minimum and maximum, and any outliers community still co-occurred with L. humile near the invasion front (Diaz et al 2014).…”

“…Previous studies have found that L. neglectus is behaviorally more aggressive than L. humile (Bertelsmeier et al 2015c), a trait that is greatly advantageous during interspecific interactions. That said, L. humile's colony density and size have increased over the course of its invasion (Diaz et al 2014). Therefore, L. humile's earlier arrival in Europe means that it could be more numerically abundant and that it might already be well established when L. neglectus arrives at a given location, which could allow L. humile to exclude L. neglectus when the two species co-occur.…”

Development of a Natural Practice to Adapt Conservation Goals to Global Change

“…A lack of knowledge would justify increased research to develop appropriate methods or provide the rationale for no intervention. For instance, in removing invasive ant populations, managers have relied on what are often ineffective and polluting pesticide application programs, but with additional research, nontoxic methods are emerging (Diaz et al 2013). Alternatively, sometimes the impacts of invasive ants decrease over time with no control measures (Morrison 2002;Cooling et al 2012).…”