Forest remnants contribute to parasitoid conservation: experimental evaluation of parasitism on a leafminer host

Abstract

Worldwide, intense forest fragmentation has resulted in mosaic landscapes in which biodiversity and a number of important ecological processes are threatened. Insect parasitism is a vital component of herbivore population regulation, hence the study of parasitism and parasitoid richness in fragmented forests embedded in an agricultural matrix is relevant from conservation and management perspectives. Here, we investigated through experimental field exposure of the leafminer Liriomyza commelinae (Diptera: Agromyzidae) the effects of forest remnant size and edge/interior location on parasitism, species richness and parasitoid community composition. Two consecutive experiments were performed in which pots with mined plants were placed in remnants of Chaco Serrano forests in Central Argentina. Parasitism levels (on average above 50 %) and number of parasitoids species (in total, 20 species) were independent of forest remnant size. However, higher parasitism and species richness were found at the forest edge compared with the interior although the differences in species richness failed to reach statistical significance. Parasitoid community composition was not related to forest size whereas assemblages from interior habitats showed closer similarity than those from the edges. The results suggest forest remnants could play an important role as reservoirs of parasitoids with potential to control crop pests, a possibility heightened by the positive edge effects which could facilitate the transfer of this valuable ecosystem service to the adjacent cultivated land.