Sasakawa Kôji, Uchijima Kenta, Shibao Harunobu, Shimada Masakazu
Department of General Systems Studies, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Naturwissenschaften. 2013 Feb;100(2):117-24. doi: 10.1007/s00114-012-1001-6. Epub 2012 Dec 5.
Many parasitoid wasps learn host-associated cues and use them in subsequent host-searching behavior. This associative learning, namely "oviposition learning," has been investigated in many studies. However, few studies have compared multiple species, and no comparative study has previously been conducted on ectoparasitoid species. We compared the effects of oviposition learning on host preference and offspring sex ratio in two closely related ectoparasitoid wasps with contrasting reproductive strategies, Anisopteromalus calandrae (r-strategist) and its sibling species (K-strategist). Using two bruchine hosts, Callosobruchus chinensis and Callosobruchus maculatus larvae infesting the cowpea Vigna unguiculata, oviposition choice experiments were performed at high and low host densities. In both species, no conspicuous effect on the offspring sex ratio was detected, but effects on host preference were found to differ between the species. In A. calandrae, the effects were detected only at high host density, suggesting that oviposition learning plays a role in host discrimination from a short distance but not from a long distance. In the sibling species, those effects were not detected in any of the cases, suggesting the absence of oviposition learning. These results are compatible with those of previous comparative studies of endoparasitoid wasps in that few lifetime oviposition experiences and/or low reward per foraging decision result in low or absent oviposition learning ability. This finding may indicate that ecological traits contributing to learning ability are similar between endoparasitoid and ectoparasitoid wasps. Thus, our species comparison of ectoparasitoids provides another model system for investigating learning and memory dynamics in parasitoid wasps.
许多寄生蜂会学习与宿主相关的线索，并在随后的宿主搜索行为中加以利用。这种联想学习，即“产卵学习”，已在许多研究中得到调查。然而，很少有研究对多个物种进行比较，之前也没有针对体外寄生蜂物种进行过比较研究。我们比较了产卵学习对两种繁殖策略截然不同的近缘体外寄生蜂——谷斑皮蠹长尾啮小蜂（r策略者）及其近缘物种（K策略者）——的宿主偏好和后代性别比例的影响。利用两种豆象宿主，即侵染豇豆的绿豆象和四纹豆象幼虫，在高宿主密度和低宿主密度条件下进行了产卵选择实验。在这两个物种中，均未检测到对后代性别比例有明显影响，但发现对宿主偏好的影响在两个物种之间存在差异。在谷斑皮蠹长尾啮小蜂中，仅在高宿主密度下检测到影响，这表明产卵学习在近距离区分宿主方面发挥作用，但在远距离时则不然。在其近缘物种中，在任何情况下均未检测到这些影响，这表明不存在产卵学习。这些结果与之前对内寄生蜂的比较研究结果一致，即一生的产卵经历较少和/或每次觅食决策的回报较低会导致产卵学习能力较低或不存在。这一发现可能表明，有助于学习能力的生态特征在内寄生蜂和体外寄生蜂之间是相似的。因此，我们对体外寄生蜂的物种比较为研究寄生蜂的学习和记忆动态提供了另一个模型系统。
