Colfer R G, Rosenheim J A
Department of Entomology and Center for Population Biology, University of California, 95616, Davis, CA, USA.
Mission Organics, P.O. Box 2357, 93902, Salinas, CA, USA.
Oecologia. 2001 Jan;126(2):292-304. doi: 10.1007/s004420000510. Epub 2001 Jan 1.
Many predatory arthropods eat both unparasitized herbivores and herbivores that are parasitized and contain the immature stages of endoparasitoids, a form of intraguild predation. Thus, the biological control of herbivorous arthropods can be either enhanced or disrupted by introducing a predator species to an existing host-parasitoid system. We evaluate the impact of introducing a predator, the convergent ladybird beetle, Hippodamia convergens, on the biological control of the cotton aphid, Aphis gossypii, by the parasitoid Lysiphlebus testaceipes, under field conditions. Predation on immature parasitoids by H. convergens was intense: 98-100% of aphid mummies were consumed by the end of the experiment, and H. convergens substantially reduced immature parasitoid populations. Despite the negative impact of H. convergens on aphid parasitoids, aphid population suppression was greatest in treatments containing both H. convergens and parasitoids. The parasitoid alone or in combination with H. convergens suppressed cotton aphids in a density-dependent manner and increased total plant leaf area and biomass, H. convergens did not substantially alter the percentage of aphids mummified by parasitoids and showed a partial feeding preference for unparasitized aphids over aphid mummies. We conclude that under conditions where a predator shows both a partial preference for unparasitized hosts and high levels of predation on unparasitized hosts, we may expect the predator to improve suppression of herbivores even if it produces high levels of intraguild predation. While intraguild predation is an important ecological interaction in the early-season cotton agroecosystem, it does not disrupt cotton aphid biological control.
许多捕食性节肢动物既捕食未被寄生的植食性动物，也捕食已被寄生且体内含有内寄生蜂未成熟阶段的植食性动物，这是一种集团内捕食形式。因此，将捕食者物种引入现有的寄主 - 寄生蜂系统可能会增强或破坏对植食性节肢动物的生物防治。我们评估了在田间条件下，引入捕食者——集栖瓢虫（Hippodamia convergens）对寄生蜂淡足侧沟茧蜂（Lysiphlebus testaceipes）对棉蚜（Aphis gossypii）的生物防治效果的影响。集栖瓢虫对未成熟寄生蜂的捕食强度很大：到实验结束时，98% - 100%的蚜虫僵蚜被吃掉，集栖瓢虫使未成熟寄生蜂的数量大幅减少。尽管集栖瓢虫对蚜虫寄生蜂有负面影响，但在同时含有集栖瓢虫和寄生蜂的处理中，对蚜虫种群的抑制作用最大。单独的寄生蜂或与集栖瓢虫组合都以密度依赖的方式抑制了棉蚜，并增加了植株总叶面积和生物量，集栖瓢虫并没有显著改变被寄生蜂寄生的蚜虫僵蚜的比例，并且相较于蚜虫僵蚜，对未被寄生的蚜虫表现出部分取食偏好。我们得出结论，在捕食者既对未被寄生的寄主有部分偏好又对未被寄生的寄主有高水平捕食的条件下，即使它会产生高水平的集团内捕食，我们也可能预期该捕食者会改善对植食性动物的抑制。虽然集团内捕食是棉花早期农业生态系统中的一种重要生态相互作用，但它并未破坏棉蚜的生物防治。
