Recent fire in a Mediterranean ecosystem strengthens hoverfly populations and their interaction networks with plants

Abstract

Fire affects many critical ecological processes, including pollination, and effects of climate change on fire regimes may have profound consequences that are difficult to predict. Considerable work has examined effects of fire on pollinator diversity, but relatively few studies have examined these effects on interaction networks including those of pollinators other than bees. We examined the effects of a severe wildfire on hoverfly pollinators in a Mediterranean island system. Using data collected over 3 consecutive years at burnt and unburnt sites, we documented differences in species diversity, abundance, and functional traits, as well as hoverfly interactions with flowering plants. Hoverfly abundance and species richness peaked during the first post‐fire flowering season (year 1), which coincided with the presence of many opportunistic species. Also in year 1, hoverfly pollination networks were larger, less specialized, more nested, and less modular at burnt (vs. unburnt) sites; furthermore, these networks exhibited higher phylogenetic host‐plant diversity. These effects declined over the next 2 years, with burnt and unburnt sites converging in similarity to hoverfly communities and interaction networks. While data obtained over 3 years provide a clear timeline of initial post‐fire recovery, we emphasize the importance of longer‐term monitoring for understanding the responses of natural communities to wildfires, which are projected to become more frequent and more destructive in the future.

Global change and plant–pollinator communities in Mediterranean biomes

“…analogous patterns were found in Spain for the years 1975-1993(Díaz-Delgado et al, 2002. If these results are alarming for the fire-adapted MTEs, the risk and consequences are unpredictable for the non-adapted Chilean matorral (Martínez-Harms et al, 2017).…”

“…For example, promising research in Israel and Greece showed that fire selected for short-tongued, aboveground nesting bees with limited foraging ranges, and late activity in the flowering season, implying that these functional phenotypes are expected to be highly abundant during the first post-fire years (Lazarina et al, 2019(Lazarina et al, , 2016Moretti et al, 2009). Similarly, recent work from Greece addressing the response of hoverfly scrubland communities across the first 3 postfire years showed that the first year was massively dominated by opportunistic, migratory species that likely arrived from adjacent, unburnt areas; meanwhile, the destruction of ecological corridors may have prevented less mobile hoverfly species from colonizing burnt landscapes (Nakas et al, 2023).…”

“…Finally, the analytical potential of empirical interaction datasets will be further enhanced by including the functional and phylogenetic diversity of assemblages for (i) determining which phenotypes promote resilience or vulnerability against different stressors (e.g. Nakas et al, 2023), and (ii) investigating the drivers of community responses (e.g. Rezende et al, 2007).…”

The response to fire by two eusocial bee species

“…Bees (Apoidea: Anthophila) are the most important pollinators in the region (Kaloveloni et al, 2018; Nielsen et al, 2011; Petanidou et al, 2013; Petanidou & Ellis, 1993; Potts et al, 2006). The effects of fire on pollinators in the Mediterranean have been studied extensively, with the majority of the studies reporting positive impacts on their populations, especially during the first postfire years (Elia et al, 2012; Lazarina et al, 2019; Moretti et al, 2009; Nakas et al, 2023; Petanidou & Ellis, 1996; Potts et al, 2003).…”

“…In terms of trophic specialisation, freshly burnt areas are known to host more generalist species compared to specialists (Lazarina et al, 2017; Nakas et al, 2023; Peralta et al, 2017). Freshly burnt sites have higher abundances of generalists than specialists bees something that Peralta et al (2017) attributed to the species' high flexibility to feed on different resources.…”