A Preliminary Study Of Host Divergence In Exotic Ophraella Communa (Coleoptera: Chrysomelidae)

Ophraella communa (Coleoptera:Chrysomelidae), originated inNorth America and a specialist on Ambrosia artemisiifolia, is found feeding and ovipositing on Xanthium sibiricum as well in recipient China. To explorer the host divergence of O. communa populations on the two plants, choice and consumption experiments were carried out. The main results are summarized below.1. Host-selection behavior of O. communa form different host sourceThe choice trials showed a significant preference for A. artemisiifolia over X. sibiricum, but such preference was also influenced by the source plants from which the testing insects were originated, as manifested by relatively over-preferences for the plant where they were collected from. The results suggested that adults source from X. sibiricum have a significant preference for choosing X. sibiricum, and provide a condition for host bio types.2. Consumption of O. communa adults from different host sourceThe feeding experiment showed that the two cohorts of insects were significantly different in the leaf consumption of sunflower but not the other test plants. The ragweed cohort showed a significant preference for A. artemisiifolia, with a consumption of leaf discs by 51.27mm in 24 hours, over the other test plants, and there were no differences in consumption between the other test plants (< 40mm2). The cocklebur cohort consumed leaf discs by 52.24 mm2 of A. artemisiifolia, which was not different from sunflower and A. trifida but more than X. sibiricum and H. tuberosus without difference between the later two plants. The results suggested that adults of ragweed cohort feeding preference of related plants differ from the ragweed cohort. 3. Consumption of O. communa larvae from different host sourceThe feeding experiment showed that the two cohorts of insects were significantly different in the leaf consumption of A. artemisiifolia, X. sibiricum and H. annuus, and the consumption of ragweed cohort were more than the cocklebur cohort. The ragweed cohort showed a significant preference for A. artemisiifolia, with a consumption of leaf discs by 5.09mm2 in 24 hours, over the other test plants. The cocklebur cohort consumed leaf discs by 2.13 mm2 of X. sibiricum, less than the other 4 plants, which was significantly different with A. artemisiifolia, H. tuberosus and A. trifida, not different from H. annuus. The experiment under the control of genetic idendity indicated that the larvae of the ragweed cohort showed much more variation in consumption of test plants than those of the cockbur cohort. The results suggested that the cocklebur cohort tend to evolve in host bio types.4. Leaf consumption by progeny larvae from mating between two cohortsO. communa was reared either on A. artemisiifolia or X. sibiricum, and reciprocal crosses in mating were made between insects from the two plants. The ensuing progeny was tested for larvae and adults in leaf consumption of the two plants. The leaf consumption of A. artemisiifolia by larvae was significantly affected by the paternal (p= 0.036) but not by the maternal effects. In contrast, the larval consumtion of X.sibiricum was significantly affected by the maternal (p<0.001), but not by the paternal effects. Maternal and paternal effects were significantly interacted in the influence of consumtion. Adult consumption of the two plants varied significantly with the source plants from which their larvae were reared, where the paternal effect was significant on leaf consumption of A. artemisiifolia (p<0.001), but not X. sibiricum. Maternal effects was significant on leaf consumption of A. artemisiifolia and X sibiricum (p<0.001). The results suggested that the influence of maternal effects is srtonger in the evolution of host bio types.