High nymphal host density and mortality negatively impact parasitoid complex during an insect herbivore outbreak

• 来源期刊: 中国昆虫科学（英文版）
• 关键词: density-dependent mortality insect outbreak psyllid synchronization temperature trophic interactions
• 年，卷（期）: 2019,（2）
• 页码范围: 351-365
• 页数: 15页
• 语种: 英文
• DOI: 10.1111/1744-7917.12532

摘要

Insect herbivore outbreaks frequently occur and this may be due to factors that restrict top-down control by parasitoids,for example,host-parasitoid asynchrony,hyperparasitization,resource limitation and climate.Few studies have examined hostparasitoid density relationships during an insect herbivore outbreak in a natural ecosystem with diverse parasitoids.We studied parasitization patterns of Cardiaspina psyllids during an outbreak in a Eucalyptus woodland.First,we established the trophic roles of the parasitoids through a species-specific multiplex PCR approach on mummies from which parasitoids emerged.Then,we assessed host-parasitoid density relationships across three spatial scales (leaf,tree and site) over one year.We detected four endoparasitoid species of the family Encyrtidae (Hymenoptera);two primary parasitoid and one heteronomous hyperparasitoid Psyllaephagus species (the latter with female development as a primary parasitoid and male development as a hyperparasitoid),and the hyperparasitoid Coccidoctonuspsyllae.Parasitoid development was host-synchronized,although synchrony between sites appeared constrained during winter (due to temperature differences).Parasitization was predominantly driven by one primary parasitoid species and was mostly inversely host-density dependent across the spatial scales.Hyperparasitization by C.psyllae was psyllid-density dependent at the site scale,however,this only impacted the rarer primary parasitoid.High larval parasitoid mortality due to density-dependent nymphal psyllid mortality (a consequence of resource limitation) compounded by a summer heat wave was incorporated in the assessment and resulted in density independence of host-parasitoid relationships.As such,high larval parasitoid mortality during insect herbivore outbreaks may contribute to the absence of host density-dependent parasitization during outbreak events.