Studying host and microhabitat use by arthropods in tropical rain forest canopies: issues & perspectives [abstract]

Abstract

Interest for canopy arthropods in tropical rain forests is a lively component of a wider scientific agenda intended to explore and understand one of the most significant, exciting and endangered habitats on Earth. In less than 20 years, this topic has emerged as a vigorous field of entomological investigations, as the ever-increasing number of publications focusing on this habitat attests. Tropical forest canopies represent fascinating environments for entomologists because (1) the species-richness of their arthropod communities is exceptional and, arguably, tropical rain forest canopies may support much of the Earth&#39;s biodiversity; (2) their entomological faunas are still largely unknown and have been the subject of much controversy among entomologists and ecologists; (3) they represent a suitable arena where biologists can study multiple species interactions within communities and test the latest hypotheses in evolution and co-evolution; and (4) rapid logging of tropical forests makes their canopy inhabitants particularly vulnerable to extinction; therefore, dissemination of scientific information to foster scientific interest on those arthropod communities is crucial before they vanish. Many of the earlier studies of canopy arthropods focused on the taxonomic distribution and species diversity of the material collected, and have relied upon indirect sampling methods, such as light trapping or canopy fogging. Often, observers were limited to ground level, with few opportunities to study canopy organisms directly. Recent methodological developments (such as construction cranes, canopy towers, canopy rafts, aerial sledges, aerial walkways or single rope techniques ) have broadened our ability to access the canopy and allow the observation and collection of canopy arthropods <I>in situ</I>. Collecting methods are accordingly much more diverse and reflect the increasing complexity of the questions that are pursued by canopy entomologists. The study of canopy arthropods has matured considerably in recent years and investigations now target specific questions, instead of comprising rather descriptive accounts. Many of the research groups are now in a position to explain how arthropods are distributed within and among tree-crowns, and how they use their food resources. A better understanding of how arthropods are distributed and use their resource in tropical canopies is crucial to refine global estimates of species richness and to facilitate management and conservation of these species-rich communities.