Distribution of insect galls in xeric and mesic habitats of Floresta Nacional de Silvânia, Brazil

<div><p>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.</p></div

Generalized linear mixed model for the effects of phylogenetic isolation (PI) and plant origin (PO) on the richness of insect herbivores, for all herbivores, for assemblages of endophages only, or for assemblages of exophages only.

<p>Positive z-values for the plant-origin effects suggest a higher richness in native plants, whereas negative values suggest a higher richness in exotic plants. Marginal (R²_m) and conditional (R²_c) r-squared values are shown. The number of observations for the entire dataset includes 728 plant species in 30 local assemblages. The number of observations for the endophagous assemblages represents 215 plant species in 13 local assemblages, and that for the exophagous assemblages represents 513 plant species in 17 local assemblages.</p

Global distribution of the 30 plant-herbivore assemblages used in this study.

<p>Green dots represent plant-insect assemblages that are composed of endophagous herbivores and red dots represent those assemblages composed of exophagous herbivores.</p

Standardized coefficients of the relationship between phylogenetic isolation (PI) and plant origin (PO) on the response variables (richness, Jaccard’s index, Simpson’s index and specialization) of insect herbivores, for all herbivores, only endophagous assemblages, or only exophagous assemblages.

<p>Positive coefficients for the plant origin effect mean higher values of the response variables on natives compared to exotic plants. Error bars represent ±1.96 standard errors.</p

Generalized mixed model for the effects of phylogenetic isolation (PI) and plant origin (PO) on the mean specialization of insect herbivores, for all herbivores, only endophagous assemblages or only exophagous assemblages.

<p>Positive t-values for the plant origin effects suggest a higher mean specialization of the herbivores on native plants, whereas negative values mean a higher suggest specialization on exotic plants. Marginal (R²_m) and conditional (R²_c) r-squared values are shown. The number of observations for the entire dataset represent 728 plant species, in 30 local assemblages; that for the endophagous assemblages represent 215 plant species in 13 local assemblages, and that for the exophagous assemblages represent 513 plant species in 17 local assemblages.</p