Abstract
In ecological systems, indirect interactions between plant pathogens and phytophagous arthropods can arise when infestation by a first attacker alters the common host plant so that although a second attacker could be spatially or temporally separated from the first one, the former could be affected. The induction of plant defense reactions leading to the production of secondary metabolites is thought to have an important role since it involves antagonistic and/or synergistic cross-talks that may determine the outcome of such interactions. We carried out experiments under controlled conditions on young rose plants in order to assess the impact of these indirect interactions on life history traits of three pests: the necrotrophic fungus Botrytis cinerea Pers.: Fr. (Helotiales: Sclerotiniaceae), the aphid Rhodobium porosum Sanderson (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Our results indicated (i) a bi-directional negative interaction between B. cinerea and R. porosum, which is conveyed by decreased aphid growth rate and reduced fungal lesion area, as well as (ii) an indirect negative effect of B. cinerea on insect behavior. No indirect effect was observed between thrips and aphids. This research highlights several complex interactions that may be involved in structuring herbivore and plant pathogen communities within natural and managed ecosystems.
Highlights
Indirect interactions potentially emerge in any community of three or more interacting species [1,2]
The present study enabled us to identify indirect interaction patterns between a plant pathogen and herbivorous arthropods
A bi-directional detrimental effect on performance was observed between B. cinerea and R. porosum, conveyed by decreased aphid growth rate and a decreased fungal lesion area, whereas no effect on performance was observed between B. cinerea and F. occidentalis or between F. occidentalis and R. porosum
Summary
Indirect interactions potentially emerge in any community of three or more interacting species [1,2]. The occurrence of indirect interactions may represent an important mechanism in determining the establishment and strength of food web interactions in any ecological system [4,5] Among indirect interactions, those that are mediated by the first trophic level, i.e. the plant, have received some attention [6,7] though only a few provisional patterns have been identified. Indirect interactions between pathogens and herbivores can occur when infestation by a first attacker changes the shared host plant in a way that affects a second attacker that is often spatially or temporally separated from the first [7]. These interactions potentially impact the life history traits of the attackers, such as herbivore performance [10,11,12,13,14] or growth of pathogenic fungi [15,16,17,18,19,20] and could be among the leading factors in terms of herbivore and pathogen population dynamics
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