Galling insect communities mediate the effects of fire on their associated parasitoid communities

Abstract

Understanding fire effects on multitrophic levels is critical to the context of changes in fire regime and climate. Insects located at higher trophic levels, like parasitoids, are more vulnerable to habitat changes than insect herbivores because they need well-established populations of their hosts to survive. Currently, fire effects on parasitoids and their interactions with their hosts are unknown. Our aim was to study the changes in abundance, richness and species composition, as well as the food web structure in a system involving parasitoids and galling insects under different fire scenarios. We asked whether potential changes in abundance, species richness and composition of parasitoid communities are explained by galled plant abundance, species richness and composition of galling insects, and how fire affects the structure of galling insect–parasitoid food webs. The highest parasitoid richness was found in the 9 years after fire scenario, whereas parasitoid abundance was not affected by fire. The parasitoid species composition in the 9 years after fire scenario was different from that in the unburned and 3 years after fire scenarios. Parasitoid communities were modulated by galled plant abundance, species richness and composition of galling insect communities. Vulnerability was significantly higher in 9 years after fire scenarios, but it increased with increasing network size. Fire affects the community of parasitoids through changes in their host communities. Differences in exclusivity to fire scenarios and diet specialisation of parasitoid species and galling insect richness may explain the patterns found. Our study supports evidence that fire creates habitats heterogeneous in the availability of hosts shaping the parasitoid communities, with a bottom-up effect in food webs. Additionally, in burned areas were recorded unique galling insect–parasitoid interactions.