An Introduction to the Diversity, Ecology, and Conservation of Saproxylic Insects

Abstract

Much like flowering plants set the stage for an explosion of herbivore and pollinator diversity, the origin of dead wood in early Devonian forests (~400 mya) was followed by an incredible diversification of life, giving rise to some of the most successful morphological adaptations and symbioses on Earth. Approximately one third of all forest insect species worldwide depend directly or indirectly on dying or dead wood (i.e., saproxylic), with major functional groups including wood feeders, fungus feeders, saprophages, and predators. Although beetles and flies dominate saproxylic insect communities worldwide, other orders are represented by a wide variety of species as well, and the composition of these assemblages varies biogeographically. Most notably, termites (Blattodea) and the subsocial beetle family Passalidae are both largely restricted to the tropics where they play a major role in the decomposition process. The large body of European research linking declines of saproxylic insect diversity to reductions in the amount of dead wood and old trees across the landscape serves as a cautionary tale for researchers and land managers working in other parts of the world. The conservation of saproxylic insects everywhere can be promoted by efforts to provide an adequate amount and variety of dead wood and old trees across space and time. The preservation of old-growth forests is also critically important as they support relict populations of the most sensitive species. There is a strong need for research outside the boreal and temperate zones to develop a more global appreciation for the diversity and ecology of saproxylic insects and to inform management strategies for conserving these organisms in subtropical and tropical forests.