Agarwala Basant K, Yasuda Hironori, Kajita Yukie
Department of Life Science, Tripura University, Agartala 799 004, Tripura, India.
J Chem Ecol. 2003 Feb;29(2):357-76. doi: 10.1023/a:1022681928142.
Growing evidence suggests a flow of chemical information from higher to lower trophic levels that affects foraging and oviposition of 'prey' in response to potential risks from predators. This was investigated in two species of ladybird predators of aphid, Harmonia axyridis and Propylea japonica. H. axyridis is known to be the stronger intraguild predator and P. japonica to be the more frequent intraguild prey in interactions of these two species. These ladybirds share aphid prey on mugworts, hibiscus, and Italian ryegrasses in fields of northern Japan but largely avoid each other on the same plant. Fecal cues of these ladybird predators were found to contribute in their assessment of predation risk from conspecific and heterospecific competitors in common habitats. Gravid females of H. axyridis reduced rates of feeding and oviposition when exposed to feces of conspecifics, but not when exposed to feces of P. japonica. In contrast, gravid females of P. japonica reduced feeding and oviposition when exposed to feces of both H. axyridis and its own species. Females of both ladybird species exhibited similar behavior in response to water extracts of feces. For P. japonica, the influence of heterospecific feces was greater than that of conspecific feces. Our results demonstrate that feces of ladybirds contain odors that have the potential to deter the feeding and oviposition activities of conspecific as well as heterospecific ladybirds. Such deterrence allows these insects to avoid predation risk. Differences in responses of the two predators are discussed.
越来越多的证据表明，存在一种从高营养级到低营养级的化学信息流动，这种流动会影响“猎物”的觅食和产卵行为，以应对来自捕食者的潜在风险。我们以两种捕食蚜虫的瓢虫——异色瓢虫和龟纹瓢虫为研究对象对此进行了调查。在这两个物种的相互作用中，已知异色瓢虫是更强的种内捕食者，而龟纹瓢虫是更常见的种内猎物。在日本北部的田野中，这些瓢虫在艾草、芙蓉和意大利黑麦草上共享蚜虫猎物，但在同一植株上大多会相互避开。研究发现，这些瓢虫捕食者的粪便线索有助于它们评估共同栖息地中同种和异种竞争者的捕食风险。异色瓢虫的怀孕雌虫在接触同种粪便时，取食和产卵率会降低，但接触龟纹瓢虫粪便时则不会。相比之下，龟纹瓢虫的怀孕雌虫在接触异色瓢虫及其自身物种的粪便时，取食和产卵都会减少。两种瓢虫的雌虫对粪便水提取物的反应表现出相似的行为。对于龟纹瓢虫来说，异种粪便的影响大于同种粪便。我们的研究结果表明，瓢虫粪便中含有气味物质，这些物质有可能抑制同种和异种瓢虫的取食和产卵活动。这种威慑作用使这些昆虫能够避免捕食风险。我们还讨论了这两种捕食者反应的差异。
