Short-term positive effects of wildfire on diurnal insects and pollen transport in a Mediterranean ecosystem

Climate change is a key driver of increased wildfire activity globally. Whilst the recovery of plant communities after fire is generally understood, the impacts on ecological processes, such as pollen transport by insects, have received little attention. We investigated the effects of wildfire on diurnal insects and pollen transport over 2 years following a large fire in Southern Portugal. By comparing samples collected at burned and adjacent unburned sites, we examined wildfire effects on (a) abundance and species richness of insects across seasons, (b) pollen being transported, (c) three of the most abundant species: Oxythyrea funesta, Heliothaurus ruficolis (both Coleoptera), and Apis mellifera (Hymenoptera). Wildfire and season had significant, interacting effects on the abundance of insects but not species richness. Abundance and species richness increased over time at both burned and unburned sites, most notably each spring. Pollen loads, and species richness, found on individual insects were significantly higher in burned sites in the first spring only, but generally increased with time after the wildfire. The abundance of O. funesta was similar between burned and unburned sites in the spring, but in the winter was significantly higher in burned sites; there were no significant differences in summer and autumn. H. ruficolis abundance was higher in burned sites. A. mellifera abundance was unaffected. Overall, across almost all the community metrics, our results suggest that wildfire affects pollen transport by diurnal insects, at least in the short term, but with time, these become similar to unburned habitats.