Studies on the ants, alien and native plants, and ant sampling methods in a United States national par

Ants have major impacts on terrestrial ecosystems throughout the world, and alien plants are markedly changing ecosystems worldwide. Alien plants make conservation programs in nature preserves increasingly difficult. To increase understanding of changes in native ant and plant communities correlated with alien-plant invasion, I surveyed ants and vascular plants over 2 yr in a riparian forest in part of a U.S. national park (Dyke Marsh Preserve, Virginia).;In the preserve, alien-plant cover was negatively correlated with the distance of sampling sites from the Potomac River. Therefore, invasion of alien plants in this forest may be the result of land clearing during flooding, propagule pressure from the river, or both. Further, the amount of cover and species richness of native plants was negatively correlated with the amount of alien-plant cover, suggesting the alien plants are negatively affecting native plants.;Pitfall trapping resulted in higher ant abundance in samples and greater ant species for a given sampling effort than soil-core samples. On the other hand, soil-core samples resulted in a higher species-per-ant ratio than pitfall-trap samples but quickly reached a species-richness asymptote at 15 ant species. In this study random site selection using GIS and GPS resulted in more ant species per pitfall-trap hour than a previous study in the same forest with the same number of pitfall traps randomly distributed within four 100-m 2 non-random locations.;Total ant richness was positively correlated with the amount of alien-plant cover, suggesting increasing amounts of alien plants can increase ant richness. The incidence of the less-common and forest-ant species was positively correlated with the amount of alien-plant cover and not correlated with total-plant cover. Therefore, the increased incidence of the less-common ant group is probably not the result of general habitat changes due to total-plant cover. These findings suggest increased resource availability due to alien-plant presence, disturbed habitat, or some other factor correlated with alien-plant cover in the forest has led to increased ant richness in sites with greater alien-plant cover.