The impact of an environmental contaminant on reproduction and development in the invasive Argentine ant, Linepithema humile.

Several factors are involved in an invasive ant species' ability to establish in its introduced range, two of which are the suitability of the habitat and the competitive ability of the invasive population. The numerical dominance of Argentine ants in their introduced ranges is thought to contribute to their competitive ability and success. In field studies we observed that Argentine ants did not occur in sites contaminated with selenium, even though native ant species were common. We therefore posed the question as to whether exposure to a toxic contaminant, such as selenium, could potentially limit an invasive population of ants through an impact on queen reproduction and brood viability. We set up 18 mini-colonies containing 1 queen and 100 workers. Each colony was provided with one of three environmentally relevant concentrations of selenium (0, 5, 10 μg Se ml^-1) administered in an artificial nectar source (25% sucrose). The number of offspring and their developmental stages were recorded weekly for each colony. Results show that queens exposed to the higher selenium concentration died sooner than queens in control colonies. Fecundity was also reduced for queens that received selenium-treated sucrose. In addition, only offspring from the control group survived to adulthood, whereas offspring from treated groups died in the larval stage. The findings of this study provide insight into the potential influence pollution may have for invasive ant species entering a habitat containing toxic contaminants, especially when that species is dependent on population numbers to outcompete native species.