Ismail Mohannad, Zanolli Penelope, Muratori Frédéric, Hance Thierry
Biodiversity Research Centre, Earth and Life Institute, Université Catholique de Louvain, Croix du Sud 4-5, 1348 Louvain-la-Neuve, Belgium.
Dipartimento di Scienze Agrarie e Ambientali, Università di Udine, Via Delle Scienze 208, 33100 Udine, Italy.
Insects. 2021 Sep 28;12(10):878. doi: 10.3390/insects12100878.
Herbivore-induced plant volatiles constitute the first indicators of insect host presence, and these can affect the foraging behavior of their natural enemies. The density of insect hosts may affect the nature and concentration of these plant-induced volatiles. We tested the impact of infestation density (low, intermediate, and high) of the pea aphid, (Homoptera: Aphididae), feeding on the broad bean , on the attractiveness of the parasitoid (Hymenoptera: Braconidae), using a Y-tube olfactometer (infested vs. non-infested plants). The emitted volatile compounds from both infested and non-infested plants were collected and identified. In addition, two series of experiments were carried out to test the impact of the presence of a conspecific female parasitoid within the aphid/plant complex on the attractiveness to other females. Parasitoids were significantly more attracted to the plants with low and intermediate aphid infestation levels. The volatile blend composition of the infested plants changed in relation to aphid density and may explain the low attraction of parasitoids toward high aphid density. The presence of conspecific females on the aphid patch had no apparent impact on the behavioral choices of other parasitoid females. Our study adds a new aspect to understanding plant-aphid-parasitoid interactions, including the possibility that aphids may manipulate chemical cues of host plants affecting the orientation of parasitoids.
植食性昆虫诱导植物产生的挥发物是昆虫宿主存在的首要指示物，这些挥发物会影响其天敌的觅食行为。昆虫宿主的密度可能会影响这些植物诱导挥发物的性质和浓度。我们使用Y型嗅觉仪（受侵染植株与未受侵染植株），测试了取食蚕豆的豌豆蚜（同翅目：蚜科）的侵染密度（低、中、高）对寄生蜂（膜翅目：茧蜂科）吸引力的影响。收集并鉴定了受侵染和未受侵染植株释放的挥发性化合物。此外，还进行了两个系列的实验，以测试蚜虫/植物复合体中同种雌性寄生蜂的存在对其他雌性寄生蜂吸引力的影响。寄生蜂对蚜虫侵染水平低和中等的植株有明显更强的趋向性。受侵染植株的挥发性混合物组成随蚜虫密度而变化，这可能解释了寄生蜂对高蚜虫密度植株趋向性较低的原因。蚜虫斑块上同种雌性寄生蜂的存在对其他寄生蜂雌性的行为选择没有明显影响。我们的研究为理解植物-蚜虫-寄生蜂之间的相互作用增添了一个新的方面，包括蚜虫可能操纵宿主植物的化学信号以影响寄生蜂定向的可能性。
