Abstract
ABSTRACT We investigated the insect gall distribution along savanna (xeric) and forest (mesic) vegetation in the Floresta Nacional de Silvânia, Goiás, Brazil. We tested if the insect gall diversity is higher in the xeric vegetation than in the mesic vegetation, as predicted by the hygrothermal stress hypothesis. The insect gall fauna was surveyed between December 2009 and June 2010 in two transects established each vegetation type. In total we found 186 insect gall morphotypes, distributed on 35 botanical families and 61 plant species. Cecidomyiidae (Diptera) induced the most insect galls (34.1%), and the plant family Fabaceae had the greatest richness of insect gall morphotypes (18). We recorded 99 insect gall morphotypes in the forest and 87 morphotypes in the savanna vegetation, being that none insect gall morphotype occurred in both habitats. We found that the insect gall richness and abundance did not differ between forest and savanna transects. On the other hand, the estimated insect gall richness was higher in the forest than in the savanna. Our findings contrary the hygrothermal stress hypothesis possibly because forest habitats have higher plant architecture complexity and occurrence of super-host taxa than the savanna habitats.
Highlights
We investigated the insect gall distribution along savanna and forest vegetation in the Floresta Nacional de Silvânia, Goiás, Brazil
Foram registrados 99 morfotipos de galhas de insetos na floresta e 87 morfotipos no cerrado, sendo que nenhum morfotipo de galha ocorreu em ambos os habitats
The Brazilian Cerrado contains a wide variety of vegetation types, ranging from forests to typical grassland formations (Ribeiro & Walter, 2008)
Summary
We investigated the insect gall distribution along savanna (xeric) and forest (mesic) vegetation in the Floresta Nacional de Silvânia, Goiás, Brazil. The Brazilian Cerrado contains a wide variety of vegetation types, ranging from forests to typical grassland formations (Ribeiro & Walter, 2008) This great vegetation heterogeneity in the Cerrado is caused by several factors, mainly variations in fire, climate, water availability and soil fertility (Oliveira-Filho & Ratter, 2002). The Cerrado constitutes a mosaic of phytophysiognomies, with many mesic (i.e., non-sclerophyllic and rich in water and nutrients) and xeric (i.e., sclerophyllic and poor in water and nutrients) vegetation types These environmental differences between xeric and mesic habitats can directly affect the distribution of insect herbivores (Neves et al, 2010; Leal et al, 2015), such as the highly specialized gall-inducing insects (Araújo et al, 2014). Because galling insects can sequester the plant secondary metabolites during gall formation as a protection mechanism against natural enemies (Cuevas-Reyes et al., 2004, 2011; Gonçalves-Alvim & Fernandes, 2001), evidences pointed that this high defense investment of xeric habitat plants favors insect gall occurrence
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