PARENT SESSION
Poster Session 30: Invertebrate Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Sampling saproxylic insects: scale issues and the importance of behavior.
Saint-Germain, Michel*,1, 2, Buddle, Christopher1, Drapeau, Pierre2, 1 McGill University, Montreal, Quebec, Canada2 Université du Québec à Montréal, Montréal, Quebec, Canada
ABSTRACT- In northern forests, it has been recognized that insects using dead wood (i.e., saproxylic insects) are important from a biodiversity perspective, but also because they significantly affect the wood decay process. Sampling and studying saproxylic insects, however, is a complicated task since they are usually cryptic for at least some part of their life cycle. Studies aiming at describing habitat affiliations of saproxylic beetles usually sample adults, even though the requirements of the larvae are much more relevant to the persistence of the species at the local scale. Since host selection does not end with attraction to host volatiles, adults must therefore be sampled as close as possible to the last step of the host-selection process (i.e., oviposition). Sticky traps placed directly on snags were used to capture adults landing on a potential host. We sampled 36 snags, including new and old snags of 5 different tree species in a single large, mixed 135 year-old boreal forest stand in western Quebec. Ordination analyses showed homogenous assemblages among contrasting snag types, either when considering all species captured or only targeted functional groups (e.g., wood-feeders). Species composition of assemblages was in several cases correlated with the species and status of trees neighbouring sampled snags, which suggest that pre-landing host-selection mechanisms does not allow insects to target a specific host while in flight. Primary attraction may play a role at larger scale and help insects to identify potential habitat patches, but the selection of a single host at the local scale may be accomplished by trial-and-error through random landing. Future studies aiming at describing host-use patterns of saproxylic insects will have to rely on more logistically-demanding methods such as rearing and wood dissection.
Key words: saproxylic insects, host-selection behavior, tree-scale sampling