Abstract

Human pressure on natural habitats increases the importance of agroforests for biodiversity conservation. The objective of this study was to evaluate the role of cacao traditional cultivation system (CTCS) on the conservation of the herbivorous insect community when compared with a monodominant rubber agroforest, a type of agricultural system for cacao cultivation. The insects were sampled in three habitats in Southeastern Bahia, Brazil: native forests, CTCS and rubber agroforests. In each habitat, 18 plots of 10 m2 were established, and the structural measures were collected and herbivorous insects were sampled with a Malaise/window trap. The diversity of folivorous decreased with the simplification of vegetation structure, but species composition was similar among habitats. In addition to a decrease in the availability of resources in monodominant rubber agroforests, the latex present in these systems have limited the occurrence of species that cannot circumvent latex toxicity. The diversity of sap-sucking insects was similar among habitats, but species composition was similar only in the CTCS and native forest, and it was different in the rubber agroforest. We observed turnover and a higher frequency of individuals of the family Psyllidae in the rubber agroforest. The biology and behavior of Psyllids and absence of natural enemies enable their diversity to increase when they are adapted to a new host. We observed a shift in the composition of xylophagous insects in the rubber agroforest compared to that in other habitats. Moreover, this agroforest has low species richness, but high individual abundance. Latex extraction is likely an important additional source of volatile compounds discharged into the environment, and it increases the attraction and recruitment of coleoborers to these sites. We concluded that CTCS has an herbivorous insect community with a structure similar to the community found in native forests of the region, and they present a more interesting conservation strategy when compared to rubber agroforests. We also emphasized the potential risk of local pest outbreaks in rubber agroforests for both the rubber and associated cacao trees.

Highlights

  • Land uses that require modification of natural habitats are the main cause of biodiversity loss in the tropics (Sala et al, 2000)

  • We tested the following predictions: i- the composition of herbivorous insects is similar between the native forest and cacao traditional cultivation system (CTCS), and different from the rubber agroforest; ii- the abundance and richness of herbivorous insects are higher in the native forest and CTCS, and smaller in the rubber agroforests; and iii- the abundance and richness of herbivorous insects are positively determined by the percentage of shade cover

  • Individuals of the family Psyllidae were highly abundant in the rubber agroforest (216) and CTCS (150) compared with the abundance sampled in the native forest (17) (Table 2)

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Summary

Introduction

Land uses that require modification of natural habitats are the main cause of biodiversity loss in the tropics (Sala et al, 2000). The CTCS undergo agricultural management that includes canopy thinning or complete removal of the shade trees, which are replaced by more productive systems (Johns, 1999; Sambuichi et al, 2012). Intensifying agricultural management by totally removing or replacing native shade trees with one or a few dominant species may negatively affect the diversity of animal groups, especially insects such as ants, butterflies (Perfecto, Mas, Dietsch, & Vandermeer, 2003), bees (Klein, Steffan-Dewenter, Buchori, & Tscharntke, 2002a), beetles (Bos, Steffan-Dewenter, & Tscharntke, 2007c) and parasitoids (Sperber, Nakayama, Valverde, & Neves, 2004). Mean annual temperature is 24-25 oC, with warmer periods from October to April (maximum of 38 oC), and colder periods from June to August (minimum 7 oC) (Mori, 1989)

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