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Linepithema humile, climate change, invasive species, optimum performance, running speed, temperature, microclimates, Bernard Field Station


The Linepithema humile, or Argentine ant, is an extremely successful and environmentally detrimental invasive ant species. However, L. humile are more susceptible to high temperatures than native ants and prefer foraging temperatures of 10˚-25˚C. We sought to examine their foraging temperature preference in the sun and in the shade at Robert J. Bernard Biological Field Station in Claremont, California. By comparing ant speeds at different temperatures, we examined the effect of temperature variance at difference microclimates on the productivity of the Argentine ant. We hypothesized that the presence of shade would decrease ant speed and therefore decrease foraging quantity. In shaded areas, where the temperature was lower, we predicted that ants will forage at a slower rate than ants in sunny areas due to the added energy cost of moving in lower temperatures. We did not find evidence to support our hypothesis. In general, Argentine ants preferred to forage in the sun and exhibited a greater average speed than in the shade, though this difference was not significant.