班氏跳小蜂对两种入侵性粉蚧的选择偏好及寄主适应机制

The loss of natural enemies in newly invaded areas is one of the key factors for the successful invasion of alien species. Aenasius bambawalei (Hymenoptera: Encyrtidae) is an obligatory accompanying parasitoid of the invasive mealybug, Phenacoccus solenopsis (Homoptera: Pseudococcidae). Interestingly, we found that A. bambawalei can parasitic another newly invasive mealybug species, Phenacoccus solani. Therefore, it is important to reveal the internal mechanisms for this phenomenon to solve the problem of loss of natural enemies in biological invasion. On the basis of previous ecological and molecular biological studies, we chose P. solenopsis and P. solani as the choice system, and addressed the following: 1) the preference of A. bambawalei to its hosts, and the relevance between parasitism rate, offspring fitness, and offspring sex ratio of the parasitoid and host size and host nutrition; 2) to determine the differences of energy reserve materials among A. bambawalei emerging from different hosts, and analyze the expression of development and reproduction relative genes, and the developmental dynamics of ovary and testis. The results of this proposal will reveal the behavioral ecology, physiological, and molecular mechanisms for host adaptation and choice preference of A. bambawalei to two invasive mealybug species, and further provide scientific ideas for making the best of parasitic wasps and solving the problem of the loss of natural enemies in biological invasion.

新侵入地的天敌缺失是外来种成功入侵的关键因素之一。班氏跳小蜂是入侵害虫——扶桑绵粉蚧的专性、伴迁性天敌，野外寄生率高达62%。我们发现该寄生蜂经过短期驯化后，能成功寄生另一种尚未有天敌报道的新入侵害虫——石蒜绵粉蚧。那么，这一有趣现象内在机制的揭示对于解决生物入侵面临天敌缺失问题有重要指导意义。在前期生态学及分子生物学基础上，本项目以扶桑绵粉蚧与石蒜绵粉蚧作为选择系统，一、测定班氏跳小蜂对不同寄主的选择偏好，明确其寄生率、子代适合度及性比与寄主营养及大小之间的关联性，揭示其寄主选择偏好的行为生态机制；二、明确分别以不同粉蚧为寄主的班氏跳小蜂，其体内能量储备物质情况，并追踪其卵巢与精巢的发育动态，比较分析与发育、繁殖相关基因的表达差异，揭示其寄主选择偏好的生理及分子机制。预计所得结果将有助于深入理解班氏跳小蜂的寄主适应机制，为充分利用寄生蜂以及解决生物入侵面临天敌缺失的问题提供科学思路。

新入侵地的天敌缺失是外来物种成功入侵的关键因素之一。在前期生态学及分子生物学基础上，本项目以扶桑绵粉蚧与石蒜绵粉蚧作为选择系统，首先研究明确了新寄主资源石蒜绵粉蚧的生物学特性，并摸清了该绵粉蚧卵型分化的产卵特性。其次，研究发现三个不同种群的班氏跳小蜂（浙江野外及室内隔离饲养种群和广西野外种群）只需要短暂适应6h就能寄生石蒜绵粉蚧的2龄、3龄若虫以及雌成虫，但是只在雌成虫上才能正常羽化出蜂；通过大、小尺度的选择性试验发现，班氏跳小蜂都会选择寄生一部分石蒜绵粉蚧，但是石蒜绵粉蚧上羽化的寄生蜂的寿命明显缩短，子代性比无显著差异；进一步发现扶桑绵粉蚧和石蒜绵粉蚧的体表挥发性物质分别有15种和21种，其中有8种化合物是一样的，但是主要化合物的含量却截然不同，初步判断该类蚧虫体表挥发物在班氏跳小蜂寄主选择过程中未必有作用。最后，在分子生物学层面发现上调基因rhodopsin在寄主转换之后6代之前上调趋势明显，6代之后基本趋于稳定；而下调基因UDP-glucose则在6代之后表现稳定，6代之前持续下调；这一结果与班氏跳小蜂寄主转换过程中雌性后代比例变化的结果相吻合，进一步说明班氏跳小蜂在6代以后可能已经完全适应了寄主转换的过程。本项目研究结果将有助于深入理解班氏跳小蜂的寄主适应机制，为充分利用寄生蜂以及解决生物入侵面临天敌缺失的问题提供科学思路。