两种近缘啮小蜂生态位分化的机理研究

Niche partitioning is the dominant mechanism for coexistence of species with overlapped resource requirements, playing a central role in maintaining biodiversity and ecosystem stability. While theoretical studies have been well made, empirical studies are still insufficient. Multiple species of parasitoids sharing a single host provides an ideal model system for testing the niche theory. The present research proposal embraces our novel model system composed of two sibling Oomyzus species parasitizing a single ladybird host of Coccinella septempuctata, and investigates how the two parasitoids share a single ladybird host. We will implement methods of insect behavioral ecology and chemical ecology; and take both laboratory and field experimental approaches to make following studies: ① seasonal dynamics of parasitism; ② oviposition strategy of the two parasitoids for the host varying in body size and age; ③ host discrimination of the two sibling parasitoids; and ④ internal competition performances of offspring parasitoids of the two species. The current research is expected to offer new evidence for the inter-specific competition in parasitoids, to complement the theory of ecological niche, and to provide solid theoretical basis for a better protection of predatory ladybirds for biological control.

生态位分化使群落中生态位重叠的物种得以共存,对于维持生物多样性和生态系统稳定至关重要。迄今，虽然相关理论研究业已成形，但仍需更多的实证研究支持和完善。分享同一寄主的近缘种寄生蜂，为生态位分化研究提供了理想模式。本项目以我们新近发现的寄生七星瓢虫的两种近缘寄生蜂（瓢虫啮小蜂和黄胫啮小蜂）为模式生物，力图阐释两种寄生蜂如何分享同一寄主瓢虫的科学问题。采用昆虫行为生态学和化学生态学方法，结合野外调查及室内实验，对以下内容开展研究：①两种近缘啮小蜂对七星瓢虫寄生作用的季节动态；②两种近缘啮小蜂对寄主（不同体型大小和龄期）的寄生选择和产卵对策；③两种近缘啮小蜂的寄主识别能力；④两种近缘啮小蜂的子代蜂在寄主体内的相对竞争力。通过研究，将为寄生蜂种间竞争理论提供新的依据，对丰富和完善生态位理论具有重要意义，也可为更好的保护常用于生物防治的捕食性天敌瓢虫提供理论依据。

当同一区域内的生物物种间有着相似的生态位、分享同样的天敌或猎物时，为避免对资源的过渡竞争导致弱势物种消失，通常会发生生态位分化。生态位分化是使得生态位重叠的物种得以共存的主要机制。然而，对于亲缘关系较近且共同寄生同一寄主的寄生性天敌，其生态位分化机理却知之甚少。本项目以瓢虫啮小蜂与孔脊啮小蜂为模式生物，利用野外调查及室内实验，探索两种近缘寄生蜂如何在分享同一寄主瓢虫情况下进行生态位分化而稳定共存的。研究结果发现两种寄生蜂对宿主寄生作用无明显的时间和空间上的分化；两种寄生蜂选择寄主寄生时，对寄主龄期无显著偏好，即在寄主资源(体型大小、龄期)上无明显分化，同时，两种寄生蜂对不同龄期的寄主有其相应的产卵策略；两种寄生蜂对是否被同种或异种寄生蜂寄生的寄主无显著、稳定的选择倾向性，即在宿主资源(被寄生状态)上，无明显分化；两种寄生蜂在寄主体内竞争时，孔脊啮小蜂是明显的弱势蜂；两种寄生蜂在不同寄主密度情况下存在竞争时，瓢虫啮小蜂的相对竞争力略强于孔脊啮小蜂。由此可以推断这两种近缘寄生蜂无明显生态位分化。研究结果为寄生蜂种间竞争提供新的依据，对丰富和完善生态位理论具有重要意义，也可为更好的保护捕食性天敌瓢虫提供理论依据。