Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 8/5/2007
Citation: Paini, D.R., Funderburk, J.E., Reitz, S.R. 2007. Competitive exclusion of a worldwide invasive pest by a native. Quantifying competition between two phytophagous insect on two host plant species. Ecology. 77(1):184-190. Interpretive Summary: The western flower thrips is one of the most damaging pests of vegetable and horticultural crops worldwide. This invasive species has become the predominant thrips species in many areas of the world, yet it remains relatively uncommon in the eastern USA. To determine the role that native thrips may play in limiting the abundance of the western flower thrips in the eastern USA, scientists with USDA-ARS Center for Medical, Agricultural and Veterinary Entomology and the University of Florida determined how competition from the native eastern flower thrips (a non-pest species) affects the survival of the western flower thrips. Survival of the western flower thrips was reduced significantly by competition from the eastern flower thrips. This intense interspecific competition may be a factor limiting the abundance of the western flower thrips.
Technical Abstract: High competitive ability is believed to be an important characteristic of invasive species. Many animal studies have compared the competitive ability of invasive species with a native species that is being displaced, but few have looked at systems where an invasive species has failed to establish itself. The thrips species F. occidentalis is a highly invasive crop pest that has spread from its original range (the western states of the US) to a worldwide distribution. Despite this, F. occidentalis is largely absent or in low numbers in the eastern states of the US, where the native F. tritici dominates. It is possible that F. tritici is competitively excluding F. occidentalis from this region. Larval competition between these two thrips species was tested on two known plant hosts, Capsicum annuum (a crop plant), and Raphanus raphanistrum (an invasive weed), using a response surface design with larval survival as the response variable. Maximum likelihood estimation was used to fit a model and generate quantitative values for competition. On both plant hosts, the invasive F. occidentalis experienced significant competition from F. tritici while F. tritici did not experience significant competition from F. occidentalis. The invasive F. occidentalis appears to be competitively excluded by the native F. tritici. This study confirms the importance of competition in the biotic resistance of a community and is one of the few animal studies to not only test for competition in an apparently resistant ecosystem but also to quantify the level of interspecific competition between two animal species.