Arthropod diversity of exotic vs. native Robinia species in northern Arizona

1. Arthropods were collected on native locust, Robinia neomexicana A. Gray, and exotic Robinia pseudoacacia L. in northern Arizona over a 2-year period to determine the number of arthropod species and number of individuals present. 2. More arthropod species were found on the native (251) than on the exotic Robinia (174). 3. Greater species diversity was likewise found on the native than the exotic. The five most numerous insects collected each year accounted for 81% to 91% of the total number collected on the exotic and native Robinia in 1997 and 1998. Only 12 species occurred on both the native and exotic Robinia in both years. 4. These findings are discussed in the context of using exotic trees in plantations and ecological theory regarding rates of arthropod species accumulation on exotic hosts.