The influence of lightning on insect and fungal dynamics in a lowland tropical forest

Abstract

Lightning strikes are a common source of disturbance in tropical forests, and a typical strike generates large quantities of dead wood. Lightning-damaged trees are a consistent resource for tropical saproxylic (i.e., dead wood-dependent) organisms, but patterns of consumer colonization and succession following lightning strikes are not known. Here, we documented the occurrence of four common consumer taxa spanning multiple trophic levels—beetles, Azteca ants, termites, and fungi—in lightning strike sites and nearby undamaged control sites over time in a lowland forest of Panama. Beetle abundance was 10 times higher in lightning strike sites than in paired control sites, and beetle assemblages were compositionally distinct. Those in strike sites were initially dominated by bark and ambrosia beetles (Curculionidae: Platypodinae, Scolytinae); bark and ambrosia beetles, and predaceous taxa increased in abundance relatively synchronously. Beetle activity and fungal fruiting bodies, respectively, were 3.8 and 12.2 times more likely to be observed in lightning-damaged trees in strike sites versus undamaged trees in paired control sites, whereas the occurrence probabilities of Azteca ants and termites were similar between damaged trees in lightning strike sites and undamaged trees in control sites. Tree size also was important; larger dead trees in strike sites were more likely to support beetles, termites, and fungal fruiting bodies, and larger trees—regardless of mortality status—were more likely to host Azteca. Beetle presence was associated with higher rates of subsequent fungal presence, providing some evidence of beetle-associated priority effects on colonization patterns. These results suggest that lightning plays a key role in supporting tropical insect and fungal consumers by providing localized patches of suitable habitat. Any climate-driven changes in lightning frequency in tropical forests will likely affect a broad suite of consumer organisms, potentially altering ecosystem-level processes.