Friend or foe: Ambrosia beetle response to volatiles of common threats in their fungus gardens

Abstract

AbstractFungus farming insects encounter multiple microbial threats in their cultivar gardens. They can affect both the nutritional cultivar and the insect’s health. In this study, we explored the potential of ambrosia beetles and their larvae to detect the presence of antagonistic or entomopathogenic fungi. The ability to recognize a threat offers individuals a chance to react. Our study organism, the fruit-tree pinhole borer,Xyleborinus saxesenii, is associated with two mutualistic fungi,Dryadomyces sulphureus(Raffaelea sulphurea)andRaffaelea canadensis. Both symbionts were tested in combinations with two common fungus-garden weeds (Aspergillussp. andPenicillium commune) and the entomopathogenBeauveria bassianain two-choice experiments. Behavioural repellence was found in many, but not all combinations. Larvae and adult females showed an opposite response to the entomopathogen, whereas forAspergillussp., neither provoked repellence nor attraction of larvae and adult females, ifR. canadensiswas used as lure. Our results validate a response of both larvae and adult ambrosia beetles towards other fungal volatiles. Their decision to confront a potential threat or preferably to avoid it could be subject to a more complex context.