IS BIGGER BETTER?. Lepidoptera body size distribution and parasitism patterns in fragmented landscapes

MONMANY, A. CAROLINA; RESTREPO, C.

San Juan

Simposio; II Symposium of Graduate Research in Biology; 2005

Universidad de Puerto Rico

Herbivore-parasitoid interactions influence plant and animal assemblages and ecosystem functions in complex ways. It has been shown that habitat fragmentation can disrupt these interactions through cascading effects. Often these effects have 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, Argentina. We measured forward wing length (FW) of 173 adult Lepidoptera belonging to 77 morphospecies. In general, FW ranged from 2 -33 mm. In continuous forest, 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.