Estrutura da vegetação determinando a diversidade de insetos herbívoros associados ao dossel de Florestas Tropicais Secas

Abstract

This study aimed to test the following hypotheses in tropical dry forests (TDFs) inserted in three vegetation domains (Brazilian savanna, Brazilian savanna-Caatinga transition and Caatinga): i. the insect herbivores community differs among the TDFs evaluated; ii. the abundance and species richness of insect herbivores are positively related with height, richness and density of trees in TDFs; iii. the local diversity (α) and the differentiation diversity between TDFs (β3) are the hierarchical components which most contribute to the regional diversity of insect herbivores (γ); iv. the tree richness has a positive effect on the differentiation diversity of insect herbivores between trees (β1). The richness and abundance of insect herbivores (chewing and sap-sucking) as well as height, richness and density of plants was estimated in each TDF. Sampling of insect herbivores associated to the canopy of trees was carried in the end of wet season. Insect herbivores community differed among TDFs, probably reflecting the floristic and structural modifications caused by the influence of different domains in each TDF. A positive effect of height and richness of tree was observed on the richness and abundance of chewing and sap-sucking herbivores, however the positive effect of density of trees was observed only for sap-sucking herbivores. The increase of structural complexity with the increment of height and richness of trees in forests promotes the coexistence of a greater number of insect herbivores species. However, the lower feeding specialization of chewing herbivores in relate to the sap-sucking possibly determined the lack of tree density effect on richness and abundance of those insects. Additive diversity partitioning of insect herbivores showed an important contribution of differentiation diversity between TDFs (β3) for regional diversity of herbivores. The differentiation diversity of insect herbivores between trees (β1) was positively affected by tree richness, corroborating the importance of plant richness on insect herbivores diversity associated in a forest. The implications of this study vary from the need to conserve TDFs in distinct vegetation domains until the need to employ approaches as such as those used in this study to other biological groups, in order to determine general patterns of diversity and to become effective future efforts to maintain the diversity in TDFs.