Four-year study of arthropod taxonomic and functional responses to a forest wildfire: Epigeic ants and spiders are affected differently

When studying forest disturbances, it is essential to examine biodiversity from different perspectives, which includes considering its taxonomic and functional facets. Indeed, different taxa may respond differently based on their functional traits. We analyzed the short-term effects of a wildfire on epigeic ant and spider communities in a Mediterranean forest. We specifically hypothesized that (1) fire would initially decrease the taxonomic and functional diversity of both taxonomic communities and have a more pronounced effect on spiders than ants because spider nests are shallower than ant nests and are consequently more vulnerable to fire; (2) recovery time would be longer for spiders than ants; and (3) the responses of taxonomic and functional diversity would be dependent on the identities and functional traits of the species found in both taxa. Our results show that wildfire affected the structure and composition of both communities but had a greater influence on ants. Over the four years of the study, these effects were largely constant for ants, whereas spiders displayed recovery. The two facets of diversity showed parallel responses to fire in the structure and composition of ant communities and in the composition of spider communities. However, the taxonomic and functional structure of spider communities reacted differently. In both spiders and ants, we observed that burned plots hosted species typical of open habitats, while unburned plots hosted species typical of vegetated habitats. We highlight the importance of (1) conducting long-term post-fire monitoring to get an accurate estimate of ecosystem recovery relative to pre-fire conditions and (2) studying taxonomic and functional responses to fire in different taxa to increase the power of the ecosystem response predictions used in habitat management decisions.