Trophic interactions among dead-wood-dependent forest arthropods in the southern Appalachian Mountains, USA
Food webs based on dead organic matter have received relatively little research attention. Here we focus deadwood- dependent (saproxylic) arthropod communities—an overlooked component of forest biodiversity that contributes to decomposition of fallen trees and nutrient cycling. First, we summarized information on factors that impact saproxylic arthropod biodiversity via a descriptive mini-review of the literature, given that the structure of food webs should be contingent upon local community composition, species richness, and/or species abundances within and among neighboring rotting logs. Next, we coupled intensive fieldwork with molecular approaches to taxonomic identification of saproxylic arthropods sampled fromrotting logs in the southern Appalachian Mountains, and synthesized information on their feeding ecology, in order to infer trophic interactions. Our mini-review highlighted major influences of local-scale (site-specific) factors affecting biodiversity, and by extension, food web structure; a pronounced publication bias toward saproxylic beetles from evergreen forests in Europe was also evident. Our empirical data on community composition of rotting logs at intermediate to late stages of decay revealed a complex food web structure. This was comprised of internal and external primary nutrient sources (deadwoodwithin logs vs. nearby living trees and fallen leaves), a diverse suite of primary consumers (wood-feeding detritivores, leaf litter-feeding detritivores, as well as herbivores and fungivores), several secondary consumer functional groups (omnivorous scavengers and ectoparasites or parasitoids), and top-level carnivorous predators that were mostly made up of spiders, opiliones, and centipedes. We close by discussing persistent challenges and limitations, and suggest future research directions.