Preliminary Studies Of Geographical Of Differentiation And Continual Oviposition Selection In Alian Ophraella Communa (Coleoptera: Chrysomelidae)

Ophraella communa LeSage is a specialist herbivorous insect of North America origin on alien invasive common ragweed, Ambrosia artemisiifolia L. (Compositae) in China. The earliest specimen of the insect was collected in May 2001, but the exact time of introduction and establishment should be earlier. It now spreads to areas south of the Yangtze and Huai rivers, and is projected to spread to areas of north and northeast of China. Alien species can be ideal model systems for the study of rapid evolution. To research into differentiation among geographical populations of O. communa, experiments were conducted to study assortativemating behaviors and genetic diversity at mitochondria DNA COI using molecular technique. The main results and conclusions are summarized as follows.1. Mating choice and offspring developmental performances between geographic populationsTo assess differentiation among geographical populations in exotic leaf beetles, O. communa, experiments were made to observe assortative mating and offspring developmental parameters between populations from east (Nanjing,32°N,118.7°E), central south (Changsha,28°N,112.9°E), and southeast (Fuzhou,26°N,119.3°E) of China. The mating choice trials showed that the probability of mating was lower between individuals from Nanjing and Fuzhou than that within populations, but not different between Nanjing and Changsha. When given choice between females from different populations, males from Nanjing and Fuzhou made more mating choices for females from their own population than from the other population, but males from Nanjing and Changsha exercised same mating choices for females from their own and the other populations. Offspring from mating between populations did not show significant differences in egg hatching, pupation, and adult emergence rates. The study suggested that some pre-mating isolation has occurred between populations from Nanjing and Fuzhou in O. communa.2. Partial sequence of COI sequences among geographic populationsInsect samples were collected from nine geographic locations, including seven from inland (Chuzhou, Nanjing, Danyang, Changsha, Nanchang, Guangdong, and Fuzhou) and two from Asian countries (North Korea and Japan). Molecular technique was used to analyze the samples in gene sequences for mitochondria DNA COI. The results showed that the popupation from Fuzhou constituted a separate line from the remaining eight lines, which formed another line. The study suggested that O. communa from Fuzhou has started to diverge from the other geographical populations examined.3. Continual oviposition selection for ragweed of different sizeTo determine whether O. communa female can select ragweeds of different quality foroviposition, trials were conducted to observe the oviposition on ragweeds of different plant size (measured ascanopydiameter) and patch size (single vs group).MANOVA results showed significant differences in the number of eggs laid in a single oviposition bout and the ensuing egg-hatching rate between the four presenting sequence treatments and the four plants exposed within a presenting sequence treatment. The number of eggs depositied was significantly less on ragweeds of four-large-size than four-small-size or size-mix. Egg-hatching rate correlated well with plant size.