Native tree facilitates the winter survival of the invasive Argentine ant

The invasive Argentine ant, Linepithema humile, has a demonstrated ability to severely disrupt agricultural, urban, and natural ecosystems within their introduced range. Argentine ants are limited in their northward expansion on the east coast of the United States by suitable winter nesting sites away from human structures. In North Carolina, the Argentine ant can escape winter temperatures by nesting in the soil. However, ambient winter temperatures severely restrict foraging opportunity. We documented Argentine ant colony winter contraction and spring expansion across an infestation in North Carolina noting that Argentine ants aggregated around loblolly pine trees, Pinus taeda, during the winter months. We found that loblolly pines facilitate the winter survival of Argentine ants in North Carolina by providing a foraging refuge to a stable honeydew resource essential for Argentine ant winter survival away from human structures. Further north, winter soil temperatures regularly fall below the Argentine ant’s foraging envelope long enough to precipitate colony collapse. The Argentine ant appears to have reached their northern range limit on the east coast of the United States due to unfavorable winter soil temperatures.