Fire affects galling insect communities through vegetation changes in a subtropical seasonally semiarid forest

Abstract

1. Fire is one of the main factors shaping vegetation characteristics around the world, with deep and complex effects on higher levels of the food web and ecosystem functioning. Specialist insects tend to be more vulnerable to fire than generalists due to their higher dependency on host plants; however, fire effects on specialist insects are still not clearly known.2. Our aim was to understand how fire-induced changes in plant richness and floristic composition modulate community features of galling insects under different fire scenarios. Specifically, we address the following questions: Are changes in galling insect richness and herbivory explained by the variation in plant richness and floristic composition under different fire scenarios? Are species composition of vegetation and galling insect communities coupled under different fire scenarios? 3. Species richness of plant and galling insect communities was higher in burned than in unburned plots, but the highest species richness was observed under different fire scenarios in both communities. Galling insect richness was better predicted by floristic composition than plant richness. Herbivory was similar under different fire scenarios and weakly related to plant richness and composition. Species composition of vegetation and galling insect communities was strongly coupled across different fire scenarios.4. The characteristics of galling insect communities were strongly affected by fire through vegetation changes, and were better explained by floristic composition than by plant richness. Our results highlight the importance of selecting areas under different fire scenarios to maximise biodiversity conservation.

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

“…Finally, how does the galling insect–parasitoid network structure vary under different fire scenarios? We expected higher parasitoid richness and abundance in burned than in unburned plots, as we previously found for galling insect richness in the same study area (Kuzmanich et al, 2022) since a higher diversity of host would increase the parasitoid richness (Kamiya et al, 2014). Since species composition of galling insects varied among fire scenarios and most of their parasitoids are specialists (Bailey et al, 2009; Dawah et al, 1995; Paniagua et al, 2009), we predicted a variation in parasitoid species composition among fire scenarios, which will be coupled with variation in species composition of galling insects.…”

“…The study was carried out in three different fire scenarios named ‘3 years after fire’, ‘9 years after fire’ and ‘unburned’, which were also used in Kuzmanich et al (2022). The ‘3 years after fire’ scenario consisted of plots burned in 2003 and 2011, except for one plot burned only in 2011 (Figure S1A).…”

“…Thus, 6, 9 and 10 plots were included for unburned, 9 and 3 years after fire scenarios, respectively. These fire scenarios were previously studied and described by Giorgis et al (2013) in terms of plant species richness, physiognomy and composition and by Kuzmanich et al (2022) in terms of plant and galling insect communities (Table S1). In these fire scenarios, burned plots (9 and 3 years after fire) are dominated by open and rich communities of grasslands and shrublands, whereas unburned plots are dominated by native and non‐native forests of shade‐tolerant plants (Giorgis et al, 2013, see Figure S1).…”

“…Indeed, recently burned areas are dominated by herbs and shrubs, and total plant richness decreases over time, whereas shrub and tree cover increases to mature forest stage (Giorgis et al, 2013, 2017; Kowaljow et al, 2019). In the studied ecosystem, we previously found that species richness and composition of galling insect communities varied in different fire scenarios, with the floristic composition being the strongest predictor of richness and composition of galling insect species (Kuzmanich et al, 2022). Thus, these fire scenarios provide an excellent opportunity to study how fire affects parasitoid communities and their interaction with their hosts.…”

“…For example, variations in the host–parasitoid food web structure can be observed when parasitoid species behave as specialists or generalists, depending on the abundance of their preferred hosts (Barbosa et al, 2017; Ferracini et al, 2018; Schönrogge & Crawley, 2000; Tylianakis et al, 2007; Xi et al, 2020). Thus, assuming that abundance and species composition of galling insects are affected by fire, a change in the network structure is expected in different fire scenarios (Bakhshandeh‐Savadroodbari et al, 2017; Cronin et al, 2020; Kuzmanich et al, 2022). In the context of human alteration of fire regimes (Andela et al, 2017; Archibald et al, 2018), gaining an understanding of how fire affects host–parasitoid interactions would be highly valuable.…”