Effect of habitat fragmentation on herbivore-parasitoid interactions: the role of body size

MONMANY, A. CAROLINA; RESTREPO, C.

Maine

Congreso; Gordon Research Conference: Metabolic basis of ecology; 2006

Bates College

Metabolic rates affect the ecology of organisms, including their interactions with the biotic and abiotic environment. Herbivore-parasitoid interactions influence other assemblages and ecosystem functions in complex ways. However, habitat fragmentation can disrupt herbivore-parasitoid interactions affecting related ecosystem functions. Often the effect of fragmentation has been measured in terms of changes in species composition, richness, and abundance. Alternatively, one may focus on changes in the distribution of body sizes. Herbivore body size has shown to be a determinant of vulnerability to parasitism. We addressed two questions. First, does habitat fragmentation affect herbivore (Lepidoptera) body size distribution? Second does fragmentation influence parasitism patterns in relation to herbivore body size? To answer these questions, we collected and reared Lepidoptera larvae from 11 forest fragments and two continuous forests in the Yungas-Chaco ecotone, NW Argentina. We measured forward wing length (FW) of 173 adult Lepidoptera belonging to 77 morphospecies. In general, FW ranged from 2 mm to 33 mm. In continuous forests, the distribution of FW seemed to be multimodal, whereas in fragmented forests it was unimodal. Large herbivore morphospecies were absent from small fragments. In all the sites, larger morphospecies seemed to be less parasitized than small ones. Intermediate and small morphospecies were parasitized in intermediate and small fragments, respectively. Our results suggest that habitat fragmentation affected herbivores targeting certain body sizes. In addition, fragmentation seems to increase the vulnerability to parasitism of small herbivores. Thus, herbivore body size may be a determinant of vulnerability to parasitism at the community level, and it should be considered in fragmentation studies.