多化性实蝇介导的不同季节宿主植物的种间相互作用

Multivoltine herbivorous insects have two or more generations each year and are widely recorded in various types of ecosystems. Different generations of multivoltine insects are often hosted by different plant species, such that multivoltine insects may induce an indirect interspecific interaction between host plant species. This has been demonstrated in agricultural system by the fact that changing the plantation area (abundance) of summer-harvested crops can modulate the population size of multivoltine insect pests and hence modulate the damage level to autumn-harvested crops. However, it is surprisingly unclear whether such multivoltine herbivorous insects mediated indirect interactions are significant between host plant species in natural ecosystems, which largely impede our understandings about mechanisms underlying plant community structure. This project aimed to explore the interactions among host plants for different generations of multivoltine tephritid flies (parasitic pre-dispersal seed predators) in Zoige alpine meadow. We would test the effects of host plant diversity, natural enemies and other univoltine seed predators as well as the environmental stresses on interactions among host plants through shared multivoltine tephritid flies. These studies may put forward the concept of a newly kind of plant species interaction that different from the classic apparent competition, and have implications for mechanisms underlying community assembly.

多化性食草昆虫一年内发生多个世代，它们不同世代的种群往往取食不同季节的植物，从而介导不同季节的植物发生间接相互作用。农田系统研究发现，调整夏熟作物种植面积（多度）可以改变多化性害虫的种群规模，进而影响秋熟作物的受害程度。然而，自然生态系统中的多化性食草昆虫能否介导不同季节的植物发生显著的种间相互作用，尚不清晰，这无疑限制了我们对群落构建和维持，尤其是展叶、开花等物候期并不重叠的植物之间共存机制的理解。本项目拟以若尔盖高寒草甸的多化性实蝇（寄生性食种子昆虫）及其不同季节的宿主植物为研究对象，通过野外调查检验生长季早、晚期的宿主植物能否影响彼此被不同世代实蝇寄生的比例，并开展若干中宇宙实验验证宿主植物、其它食种子昆虫、天敌昆虫的物种多样性和环境因子对不同季节宿主植物种间相互作用的影响。研究结果有望概念化自然群落中一种不同于典型似然竞争的种间关系类型，提升我们对群落物种多样性和稳定性的理解。

多化性昆虫在一个生长季内可以完成两个或更多个世代，这一类昆虫在自然界非常普遍，从热带到寒温带的多种生态系统中均有多化性昆虫的分布，多化性现象发生在昆虫纲的多个类群，它们在生长季不同的季节常常与不同的宿主植物和天敌发生相互作用。本项目旨在认识影响多化性昆虫种群动态的关键机制，以及由多化性昆虫介导的物候并不重叠的植物之间的间接相互作用，提升我们对于生态系统时空结构和功能的认识。..项目执行期间，我们以青藏高原东缘的高寒草甸上“菊科植物-实蝇/-寄生蜂”食物链为研究对象，系统调查了该食物网中多化性昆虫的类群和多样性，及其在生长季早、晚期的宿主植物。通过若干野外中宇宙实验揭示了植物和寄生蜂调控多化性昆虫种群动态的关键机制以及多化性昆虫对植物群落结构的影响。主要发现有：（1）宿主植物和寄生蜂分别通过资源竞争和似然竞争对多化性昆虫产生上、下行调控作用，多化性昆虫的宿主转移对维持其种群稳定具有重要作用；（2）多化性昆虫与优势和稀有植物之间分别形成对称和不对称的相互作用，是食物网中抑制优势植物的关键因子；（3）生长季中期，多样化的宿主植物在一定程度上稀释了多化性昆虫，导致部分昆虫发生“产卵错误”，而延缓了种群增长。..上述成果在一定程度上提升了我们对于多化性昆虫与不同季节宿主植物互作，以及不同季节里天敌和宿主植物之间的间接相互作用等科学问题的认识。