Species richness and abundance of defoliating Lepidoptera associated with Eucalyptus grandis in Brazil and their response to plant age

The present paper documents patterns of species richness and abundance in Lepidoptera associated with a Eucalyptus grandis plantation, and how these patterns relate to plant age. The large number of species collected (1385), the lack of dominant species and the absence of pest outbreaks during the survey may be related to the high level of plant diversity of the native forest reserves in the area. There was no clear pattern of seasonal variation in species richness, but there were seasonal fluctuations in abundance, with minor defoliator species prevailing in October at the start of the rainy season. Species richness and abundance of Lepidoptera were positively correlated, with both variables decreasing in older plantations. However, the greatest numbers of major outbreak species and minor eucalypt defoliators were observed in plants after the mid-point (6 years old) of their cutting cycle (7-10 years). This may be because of a larger amount of better-quality plant leaves after this mid-point or the reduction in silvicultural management interventions at this period of the Eucalyptus cutting cycle. The abundance of the main outbreak species observed in the survey, Stenalcidia grosica Schaus (Geometridae), was negatively correlated with plant age. Nonetheless, the effect was weak (r = - 0.21, P = 0.03) and we were not able to find further significant correlations between plant age and abundance of the other most frequent and constant species that were collected.