Gielen Robin, Põldmaa Kadri, Tammaru Toomas
Entomology Unit Department of Zoology Institute of Ecology and Earth Sciences Faculty of Science and Technology University of Tartu Tartu Estonia.
Mycology Unit Department of Botany Faculty of Science and Technology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia.
Ecol Evol. 2022 May 24;12(5):e8926. doi: 10.1002/ece3.8926. eCollection 2022 May.
Natural enemies shape the fate of species at both ecological and evolutionary time scales. While the effects of predators, parasitoids, and viruses on insects are well documented, much less is known about the ecological and evolutionary role of entomopathogenic fungi. In particular, it is unclear to which extent may the spatiotemporal distribution patterns of these pathogens create selective pressures on ecological traits of herbivorous insects. In the present study, we reared three lepidopteran species in semi-natural conditions in a European hemiboreal forest habitat. We studied the probability of the insects to die from fungal infection as a function of insect species, food plant, study site, (manipulated) condition of the larvae, and the phenological phase. The prevalence of entomopathogenic fungi remained low to moderate with the value consistently below 10% across the subsets of the data while as many as 23 fungal species, primarily belonging to the families Cordycipitaceae, Aspergillaceae, and Nectriaceae, were recorded. There were no major differences among the insect species in prevalence of the infections or in the structure of associated fungal assemblages. The family Cordycipitaceae, comprising mainly obligatory entomopathogens, dominated among the pathogens of pupae but not among the pathogens of larvae. Overall, there was evidence for a relatively weak impact of the studied ecological factors on the probability to be infected by a fungal pathogen; there were no effects of food plant, study site, or phenology which would be consistent over the study species and developmental stages of the insects. Nevertheless, when the prevalence of particular fungal taxa was studied, was found infecting insects fed with leaves of only one of the food plant, spp. Feeding on a particular plant taxon can thus have specific fitness costs. This demonstrates that fungus-mediated effects on insect life history traits are possible and deserve attention.
天敌在生态和进化时间尺度上塑造着物种的命运。虽然捕食者、寄生蜂和病毒对昆虫的影响已有充分记载，但关于昆虫病原真菌的生态和进化作用却知之甚少。特别是，尚不清楚这些病原体的时空分布模式在多大程度上会对植食性昆虫的生态特征产生选择压力。在本研究中，我们在欧洲半寒温带森林栖息地的半自然条件下饲养了三种鳞翅目昆虫。我们研究了昆虫因真菌感染而死亡的概率，该概率是昆虫种类、食草植物、研究地点、（人为控制的）幼虫状态以及物候期的函数。昆虫病原真菌的患病率一直较低到中等，在数据子集范围内该值始终低于10%，同时记录到多达23种真菌，主要属于虫草科、曲霉科和丛赤壳科。在感染患病率或相关真菌群落结构方面，昆虫种类之间没有重大差异。主要由专性昆虫病原菌组成的虫草科在蛹的病原体中占主导地位，但在幼虫的病原体中并非如此。总体而言，有证据表明所研究的生态因素对被真菌病原体感染的概率影响相对较弱；食草植物、研究地点或物候期对所有研究物种以及昆虫发育阶段均无一致的影响。然而，当研究特定真菌类群的患病率时，发现仅有一种食草植物（ spp.）的叶子喂养的昆虫被感染。因此，以特定植物类群为食可能会产生特定的适合度代价。这表明真菌介导对昆虫生活史特征的影响是可能的，值得关注。
