Submitted to: Ecological Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2010
Publication Date: 2/5/2011
Citation: Northfield, T.D., Paini, D.R., Reitz, S.R., Funderburk, J.E. 2011. Within plant interspecific competition does not limit the highly invasive thrips, Frankliniella occidentalis in Florida. Ecological Entomology. 36:181-187. Interpretive Summary: When species are introduced to new environments, they often must compete with native species. This interspecific competition is a component of the biotic resistance of the ecosystem that invaders must overcome to successfully establish, and superior competitive ability has often been cited as a major reason for the success of invasive species. However, little is known of systems in which a highly invasive species has failed to invade and dominate. These types of studies are vital however, as they provide an alternative test for the importance of competition in invasion success and biotic resistance. Since the 1970’s the western flower thrips Frankliniella occidentalis has invaded agricultural areas in much of the world and it has become the dominant thrips species in many of these areas. In Florida, however, F. occidentalis has failed to establish as the dominant species despite repeated introductions. To better understand the factors limiting the distribution and abundance of the western flower thrips in Florida, scientists with the University of Florida, CSIRO and the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology,Gainesville,Florida, examined interspecific competition between the invasive western flower thrips and the native Florida flower thrips, Frankliniella bispinosa, which is the predominant flower thrips in peninsular Florida. Results of these studies indicated that the Florida flower thrips may not be competitively superior to the western flower thrips. These results contrast with a previous study showing that another native thrips was competitively superior to the western flower thrips and therefore may limit its abundance in elsewhere in the eastern USA. Consequently, other factors may be contributing to biotic resistance to the western flower thrips in Florida.
Technical Abstract: 1. Competitive superiority is often cited as the main reason for the success of an invasive species. Although invaded ecosystems are often examined, few have studied areas in which an invasive species has failed to invade. 2. The western flower thrips, Frankliniella occidentalis, is a damaging pest and tospovirus vector that has invaded most of the world, and competitive superiority is considered one of the main reasons for this species’ success. 3. However, a recent study demonstrated that competition between larval F. occidentalis and a native thrips species may be limiting F. occidentalis abundance in much of the eastern United States. Frankliniella occidentalis also has a limited abundance central and southern Florida, which is dominated by the endemic F. bispinosa. We assessed the potential for interspecific competition to limit F. occidentalis abundance in Florida. 4. We quantified the effects of competition between F. occidentalis and F. bispinosa on adult reproduction on a common host (Capsicum annuum), using a response surface experimental design and a combination of linear and non-linear competition models. 5. We found evidence of asymmetric competition between these thrips species, but contrary to expectations, F. occidentalis reproduced more in dense interspecific populations than F. bispinosa. These results suggest that, unlike most of the eastern US, competitive resistance is not important in limiting F. occidentalis abundance in central and southern Florida. We discuss these findings in light of recent studies that indicated that predation from a generalist predator is an important limiting factor of F. occidentalis abundance in Florida.