Has egg location influenced the radiation of Diplolepis (Hymenoptera: Cynipidae) gall wasps on wild roses?

The oviposition sites of 6 species of gall wasps of the genus Diplolepis on their host roses in Ontario, Canada were examined using plant histological techniques. A leaf galler, Diplolepis polita , and a stem galler, D. triforma , gall Rosa acicularis ; whereas the leaf galler D. bicolor and the stem gallers D. nodulosa , D. spinosa and D. fusiformans gall R. blanda. D. polita and D. bicolor deposit their eggs on developing leaflets within leaf buds. D. nodulosa , D. triforma , and D. spinosa deposit their eggs between the leaf primordia near the apical meristem of leaf buds. D. fusiformans deposits eggs on the surface of current-year stems. We consider leaf buds as adaptive zones. The precise deposition of eggs within these organs contributes to species-specific differences in gall structure, and may have influenced radiation of the genus. Inquilines and parasitoids are not deterred by differences in gall structure, and thus it appears that enemies are not driving forces in the radiation of these cynipids.