森林生态系统中植食性昆虫与寄主的互作机制、假说与证据

围绕"多样性稳定性"假说、"联合抗性假说"、"生长势假说"、"胁迫假说"、以及下调、上调和推拉等机制与假说提出的背景与实验验证的证据,力图辨析其概念以及它们之间的相互关系。作者认为,多样性-稳定性机制关注森林生态系统的功能,是基于群落甚至景观层次。多样性条件下的联合抗性机制和联合易感性应属于稳定性中的抵抗力范畴。联合抗性机制的主要基础是基于资源集中假说和天敌假说,这些观点在种群层次上更易理解;上调力和下调力机制是以食物网底部的资源与顶端的天敌来探讨这种互作关系。因此,资源集中与上调力有着对应关系,而天敌假说只是下调力机制中的一个层面而已。植物生长势假说和植物胁迫假说力图从植物个体或种的群体的生长状态出发解析植食性动物的对寄主的选择趋势。上述有关植食性昆虫与寄主互作的机制、假说与证据是基于不同的层面提出的,因而在解析研究目标时,由于基本面的差异有可能会得出不同的结论。以近年来的研究进展和研究成果为依据有针对性地阐述这些理论对森林有害生物生态调控技术的指导作用,其中,联合抗性和联合易感性理论对指导森林有害生物生态控制具有更直接的指导作用。进一步提出了相应的亟待解决的科学问题。

Mechanism, hypothesis and evidence of herbivorous insect-host interactions in forest ecosystem

This paper analyzed the concepts, different mechanisms of herbivorous insect-host interactions and hypotheses based on their academic origins and recent experimental evidence. The theories we analyzed include diversity-stability mechanism, associational resistance hypothesis, associational susceptibility hypothesis, plant vigor hypothesis, plant stress hypothesis, bottom-up forces, top-down forces, and push-pull mechanism, etc. Diversity-stability mechanism focuses on functioning of forest ecosystem that is developed using evidence collected at community and landscape scale. Associational resistance and associational susceptibility is a resistance type of diversity-stability. The foundation for associational resistance hypothesis was built based on resource concentration hypothesis and natural enemy hypothesis. The resource concentration hypothesis predicted that herbivores were more likely to be found in patches where their host plants were abundant. The enemy hypothesis can explain why herbivores are fewer in forest ecosystems with a more abundant and diverse community of natural enemies. This was consistent with the diversity-stability hypothesis, which predicts that a community becomes more stable with higher diversity. These theories were easily understandable at population scale. Bottom-up forces and Top-down forces discuss the interaction between herbivorous insects and host plants along the food chains, in which bottom-up refers to restriction mechanism caused by resources on the bottom of food web while Top-down refers to natural enemies on the top of food chain. Therefore, there was a corresponding relationship between resources concentration hypothesis and bottom-up forces, and enemy hypothesis corresponds to top-down forces. Plant vigor hypothesis and plant stress hypothesis predict that herbivores tend to select host plants based on their growth conditions population size. The above herbivore-host interaction theories are proposed based on different levels in a forest ecosystem, which might result in different conclusion due to the differences in ecosystem levels. This paper then elaborated the guiding roles of these theories on forest pest control based on recent progresses. Among these theories, Associational resistance and associational susceptibility may be applicable to guide forest management, specifically forest pest control. The evidence suggested that associational resistance and associational susceptibility interactions may be mediated by biotic and abiotic mechanisms. However, there were few studies on how habitats, the spatial and temporal availability of resources determine landscape-level impacts of associational resistance and associational susceptibility, and how the strength, consistency, and relative impact of associational resistance and associational susceptibility on plant fitness vary temporally and spatially as environmental conditions, herbivore and plant abundance change. These are the questions urgently needed to be answered in this field.