Non-native plants reduce abundance, richness, and host specialization in lepidopteran communities KARIN T. B URGHARDT, 1, DOUGLAS W. TALLAMY ,CHRISTOPHER PHILIPS, 2 AND K IMBERLEY J. S HROPSHIRE Entomology and Wildlife Ecology Department, University of Delaware, Newark, Delaware 19716 USA Abstract. The impact of non-native plant invasions on ecosystems has been controversial because obvious local effects have not yet led to the global extinction of any native plant species on continents and large islands.We suggest that extinction is not the appropriate measure of impact on ecosystem function and presentevidence that non-native plant invasions or the replacement of native plants with non-native ornamentals results in significant bottom-up reductions of energy available for local food webs.Using replicated common gardens we compared Lepidoptera species richness and abundance on native plants, non-native congeners of those natives, and non-native species with no close relatives in the study area. Non-native plants supported significantly fewer caterpillars of significantly fewer specialist and generalist species even when the non-natives were close relatives of native host plants. However, the effect size was smaller in the latter category indicating phylogenetic similarity to local natives may positively impact herbivory.Clusteranalysis revealed that a non-native plantcongeneroften supportsa lepidopteran community that is a subset of the similar, but more diverse community found on its native congener. The proportion of the Lepidoptera community consisting of specialist species was about five times larger across native specieswithin sites compared to non-native plant species.In addition, speciesaccumulation trajectoriessuggested that in a fully sampled community the differencesbetween the Lepidoptera supported by native and non-native plants may be even greater than presented here. Key words:biodiversity;caterpillar;ecosystem services; food webs;invasive species; Lepidoptera; native plants; non- native plants; northeastern United States. Received 13 August2010;revised 30 September 2010;accepted 9 October2010;published 18 November2010. Corresponding Editor: D. P. C. Peters. Citation:Burghardt,K. T.,D. W. Tallamy,C. Philips,and K. J. Shropshire. 2010.Non-native plants reduce abundance, richness,and host specialization in lepidopteran communities. Ecosphere 1(5):art11. doi:10.1890/ES10-00032.1 Copyright: Ó 2010 Burghardt et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits restricted use, distribution, and reproduction in any medium, provided the original author and sources are credited. 1 Present address: Ecology and Evolutionary Biology Department, Yale University, New Haven, Connecticut 06520 USA. 2 Present address: Entomology Department, Virginia Tech, Blacksburg, Virginia 24061 USA. E-mail: karin.burghardt@yale.edu I NTRODUCTION Non-native plant genotypes (those that evolved outside of local food webs) have replaced native plant communities to a greater or lesser extent in every North American biome, as well as in anthropogenic landscapes where they have been planted by the millions as ornamentals (Williamson 1996, Qian and Ricklefs 2006). Although it has been shown that the large- scale addition of non-native plants to ecosystems can alter soil moisture, pH, biota,and nutrients; and increase fire frequency and plant competi- tion (Tyser and Worley 1992, Randall 1996, Duncan 1997,Wilcove et al. 1998,Gould and Gorchov 2000,Mack et al. 2000,Brooks et al. 2004,Butler and Cogan 2004 and many more), the ecologicalimpacts ofand our response to non-native plants has become increasingly con- troversial. One of the sources of this controversy comes from defining ‘‘impact’’ in terms of native plant v www.esajournals.org 1 November 2010 v Volume 1(5) v Article 11