Aim Introduced plant species are less likely to be attacked by herbivores than are native plant species. Isolated oceanic islands provide an excellent model system for comparing the associations between herbivore species and plant species of different residency histories, namely endemic, indigenous (non-endemic) or introduced (naturalized or cultivated) species. My aim was to test the prediction that, on isolated oceanic islands, introduced plant species have a lower tendency to have an association with insect herbivores than do endemic and indigenous plant species.
Location Ogasawara (Bonin) Islands in the western Pacific Ocean.
Methods I examined the presence/absence of leaf-mining and leaf-galling insect species on 71 endemic, 31 indigenous, 18 naturalized and 31 cultivated (introduced but not naturalized) species of woody plants from 2004 to 2008.
Results Leaf-mining insect species were found on 53.5%, 35.5%, 11.1% and 16.1% and leaf-galling species were found on 14.1%, 9.7%, 5.6% and 0% of endemic, indigenous, naturalized and cultivated plant species, respectively. Species of Lepidoptera (moths) and Hemiptera (primarily psyllids) comprised the dominant types of leaf miners and leaf gallers, respectively.
Main conclusions The incidence of leaf miners and leaf gallers differed as a function of residency history of the plant species. Introduced (naturalized and cultivated) species were less frequently associated with leaf miners and leaf gallers than were native (endemic and indigenous) species, indicating that the leaf-mining and leaf-galling insect species, most of which feed on leaves of a particular native plant genus (i.e. they show oligophagy), have not yet begun to utilize most introduced plant species.