Why some plants host more species of Lepidoptera than others: How natural enemies and native lineage influence Lepidopteran use of native and alien plants
Date
2010
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Publisher
University of Delaware
Abstract
Alien plants continue to replace native vegetation throughout North America at an alarming rate, yet we lack a firm understanding of how well alien species are performing the ecological roles of the native species they are replacing. I conducted a two year study designed to measure the impact of alien plants on native insect communities. Specifically, I investigated 1) the relationship between lepidopteran larval abundance and braconid parasitoid abundance on native and alien plant species in 13 genera of plants and on 17 alien and 15 native plant species that were unrelated; 2) the degree to which the size of the native host lineage predicts native lepidopteran host use of alien plants in the same lineage; and 3) why some plants host more species of Lepidoptera than other plants.
Using previously published data, I found a significant positive relationship between the number of native congeners and the number of Lepidoptera species a plant genus can support. This relationship was not present at the family level, or in field collected abundance data. I found no overall difference in larval abundance on closely related alien and native plants, although there were significantly more larvae on alien plants during the first year of the study. I did, however; find significantly fewer larvae on alien plants with no native congeners. I also observed a significant negative correlation between braconid abundance in 2007 and lepidopteran larval abundance in 2008.
The results of this project lend support to Darwin’s idea that more relatives in the native plant community translate to higher levels of attack from native insect herbivores. These results will help land managers and landscapers choose plants that will improve the ability of managed landscapes to support a functioning ecosystem.