The impact of non-native woody plants on the native herbivorous insect community of northern Delaware
Date
2006
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Publisher
University of Delaware
Abstract
Plants have been introduced to the United States for hundreds of years and are hypothesized to negatively impact native herbivorous insects. I tested this hypothesis by conducting a 2-year experiment in which native insect biomass production, native insect diversity, and native insect species richness was determined for native and non-native plants. A plot containing 45 species of woody plants with ten replicates each was set up in White Clay Creek state park for the purpose of this study. The plants consisted of 15 native species (Natives), 15 non-native species, which were congeners of the natives (Non-native Congeners), and 15 non-native species that did not have a native congener present in the United States (Aliens). Herbivorous insects were sampled three times during the summer of 2004 and 2005, identified, and weighed. ☐ In 2004, I found a difference in insect biomass per plant biomass production among the three groupings; Native, Non-native Congener, and Alien, but was unable to determine differences between the groups. In 2005 again there were differences among the three groupings and this time I could determine differences between the groupings. Native plants produced more insect biomass per plant biomass than Non-native Congeners or Aliens. However, insect biomass per plant biomass production between native and non-native congeneric pair members varied depending on the comparison: either the native member had more insect biomass per plant biomass, the non-native member had more insect biomass per plant biomass, or there was no difference between the two species. In 2004 insect diversity tended to be greater on Natives than on Aliens, but there was no difference between Natives and Non-native Congeners or between Nonnative Congeners and Aliens. Insect diversity was greater on Native species than on Alien species in 2005, but there was no difference between Natives and Non-native Congeners or Non-native Congeners and Aliens for that year. There was no difference in species richness among Native, Non-native Congener, and Alien plant species for either 2004 or 2005. ☐ Overall, non-native plants had a negative impact on the native insect community (insect biomass production and insect diversity), but not all non-natives were detrimental to the insects. The relatedness of non-natives to native plants (whether they are in the same genus or not) also had an impact on how strongly the herbivorous insect community was impacted.