Comparison of arthropod associates of French broom, Genista monspessulana (Linnaeus) (Fabaceae), and native shrubs on Mt. Tamalpais, Marin County, California, U.S.A.

Abstract

The hypothesis that native plants have more arthropod associates than introduced plants was tested in chaparral and coastal scrub habitats which were being invaded by the exotic shrub Genista monspessulana (Linnaeus) (Fabaceae). Paired beat samples were taken from the shrubs. Data were analyzed by use of the Wilcoxon matched-pairs nonparametric method. Native shrubs had significantly more arthropod individuals and species associated with them than G. monspessulana. Most of the species collected on the exotic broom were native generalist herbivores, omnivores or predators, except for one native specialist herbivore and one exotic specialist herbivore that originated in the native range of G. monspessulana. The first was Uresiphita reversalis (Guenee, 1854) (Lepidoptera: Crambidae) and the second was Arytainilla spartiophila (Foerster, 1848) (Hemiptera: Psyllidae). These results suggest that efforts to control invasions of G. monspessulana into areas of native shrubs are warranted to conserve biological diversity.