Composición, riqueza de especies y abundancia de insectos defoliadores de actividad nocturna asociados a Aristotelia chilensis (maqui) en el bosque maulino fragmentado

Abstract

At the Maulino forest, herbivory upon Aristotelia chilensis (maqui) is negatively affected by forest fragmentation, being higher in the continuous forest than in the small remnant fragments, particularly at the beginning of the growing season (spring). This phenomenon may be attributable to changes in the population dynamics of herbivores, mostly insects. In this work, the effect of the Maulino forest fragmentation on the abundance, species richness and composition of nocturnal defoliating insects associated with A. chilensis was evaluated. The insects associated with A. chilensis were sampled monthly, between August 2005 and February 2006, in 32 trees located in a continuous forest (600 ha) and in 32 trees located in eight forest fragments (0.4-20 ha). Insect sampling was carried out during the first five night hours. 890 folivorous insects from 17 families and 77 species of Coleoptera, Orthoptera and Lepidoptera were collected. All species were native. The total abundance did not vary with habitat fragmentation. Nevertheless, some species increased their abundance with fragmentation, while others were depressed. The species richness of folivorous insects per tree did not vary with forest fragmentation, though the total number of species was considerably higher in the forest fragments. The species similarity was higher within the continuous forest than between the continuous forest and fragments or among fragments. At the beginning of the season (September), the abundance of Sericoides obesa was significantly higher in the continuous forest than in the forest fragments. Later in the season, Sericoides viridis became more abundant in the forest fragments. Because of the body size and the voracity of Sericoides sp., these insects seem to be responsible of the herbivory patterns of A. chilensis at the Maulino forest.