Time-since fire and cynipid gall wasp assemblages on oaks

Abstract

Fires are ubiquitous features of many terrestrial ecosystems and can greatly impact the structure and evolution of plant communities. However, much less is known about how fire history impacts higher trophic levels. Using detailed records on the history and intensity of fires at the Archbold Biological Station (ABS) in central Florida, USA, we examined how time-since-fire affects the cynipid gall wasp assemblage (Hymenoptera: Cynipidae) associated with four oak species (Quercus) that are dominant components of the plant community in this region. Cynipid abundance, richness and diversity were quantified from 1249 oak trees/shrubs in 20 sites that varied in time-since-fire from 1.5 to 91 years. Among all sites and oaks, we found 24 species of cynipids and there was very little species overlap among oak species, even within the same site. Gall abundance increased with time-since-fire and was correlated with tree height, suggesting that available host material or plant architecture may be a primary driver of cynipid recovery. Within 3 years of a fire, 14 of the 23 cynipid species were detected among the sites, and by seven years since fire, all but two species could be detected. Overall, species richness and diversity reached an asymptote within ≈ 7 years. Given how quickly the cynipid assemblage recovers after a fire, frequent fires at ABS are unlikely to negatively impact these insects. However, in smaller or more isolated scrub-oak fragments, recovery could be much slower.