Niches of saproxylic weevils (Coleoptera: Curculionidae) in French Guiana

Abstract

The loss of tropical forests has a direct effect on saproxylic beetles through the loss of larval feeding substrates and an indirect effect through microclimate change in forest fragments. Impacts will be exacerbated by climate change, and species with narrow niches will be particularly vulnerable. This study presents baseline data on niches (seasonality, host plant, stratum, and branch diameter) of saproxylic weevils in a minimally disturbed moist forest of French Guiana. Weevils (excluding bark beetles) were expected to be host specialists and more abundant in moist microhabitats. Bait branches from three species in the Brazil nut family (Lecythidaceae) were exposed during the dry and rainy season at ground and canopy stratum. They yielded 1,262 weevils in 24 species; 95% belonged to the subfamily Conoderinae. Weevils emerged in greatest abundance from Eschweilera coriacea (A. P. de Candolle) S. A. Mori and from branches in the coolest, moistest microhabitat: ground stratum during the rainy season. Shifts towards warmer, drier climatic conditions would probably have a negative impact on most saproxylic weevil species currently associated with the Brazil nut family. Although this family is expected to suffer under biotic homogenization, the favored host species is hyperdominant throughout Amazonia; climate permitting, E. coriacea could provide a refuge.