Entomofauna Associated with Agroforestry Systems of Timber Species and Cacao in the Southern Region of the Maracaibo Lake Basin (Mérida, Venezuela).

Ramón Jaimez,Marina Mazón,Néstor Gutiérrez,Daniel Sánchez-Angarita,Francisco Díaz

doi:10.3390/insects9020046

Abstract

Agroforestry systems are environment-friendly production systems which help to preserve biodiversity while providing people with a way of earning a living. Cacao is a historically important crop in Venezuela that traditionally has been produced in agroforestry systems. However, few studies have evaluated how different trees used in those systems affect the dynamics and abundance of insects. The present study evaluated the entomofauna assemblages associated with different combinations of four timber-yielding trees and four Criollo cacao cultivars established in a lowland tropical ecosystem in Venezuela. A randomized block design with two replicates was used, each block having 16 plots which included all 16 possible combinations of four native timber trees (Cordia thaisiana, Cedrela odorata, Swietenia macrophylla, and Tabebuia rosea) and four Criollo cacao cultivars (Porcelana, Guasare, Lobatera and Criollo Merideño). Insects were collected with yellow pan traps and sorted to order. Coleoptera and parasitoid Hymenoptera were determined to the family level. In total, 49,538 individuals of seven orders were collected, with Hymenoptera, Diptera, and Hemiptera being the most abundant, although only Lepidoptera and Coleoptera abundances were significantly influenced by the timber tree species. Twenty-three families of parasitoid Hymenoptera and 26 of Coleoptera were found. Significant differences in insects’ assemblages were found both in parasitoid Hymenoptera and Coleoptera families associated to every shade tree, with the families Eulophidae and Lycidae being indicators for Cordia, and Chalcididae for Swietenia. The entomofauna relationship with the cacao cultivar was barely significant, although Scydmaenidae and Scarabaeidae were indicators for Lobatera and Merideño, respectively. No significant effects were found for interaction with cacao cultivars and native trees. We concluded that the particular insect assemblages found in Cedrela odorata and Cordia thaisiana, together with their high growing rates, make these two species an optimal choice for cacao agroforestry systems.

Highlights

Deforestation in Venezuela has greatly increased in the last few decades, with about326,000 hectares of native forests being destroyed per year for agricultural and livestock purposes with the aim of helping to guarantee the “food and agriculture security” of the country [1]
The aims of this study were: (1) to assess insect richness and abundance at different taxonomic levels in the agroforestry system of Criollo cacao cultivars with native timber trees; and (2) to evaluate the influence of the native timber trees and the cacao cultivars over the insect assemblages associated
The entomofauna associated with the agroforestry system studied included the major insect orders, with samples being dominated by Hymenoptera, Hemiptera, and Diptera

Summary

Introduction

Deforestation in Venezuela has greatly increased in the last few decades, with about326,000 hectares of native forests being destroyed per year for agricultural and livestock purposes with the aim of helping to guarantee the “food and agriculture security” of the country [1]. Cacao crops have been traditionally cultivated under shade conditions, but presently there is an active debate amongst both scientists and farmers as to whether the cacao crop should be placed under shade conditions or not [4,5,6,7,8] Physiological traits such as the photosynthetic rates of cacao, which are saturated at low photosynthetic photon flux densities (400–600 μmol photons m−2 s−1 ), and low leaf stomatal conductance (gs ) help explain why cacao is a shade-tolerant species [9,10,11,12], and why it benefits by growing under the shade of other trees [13]. Shade varieties may have more advantages than disadvantages [4,7], as long as shade trees contribute additional benefits [15,16], do not compete with cacao for light or nutrients, and are properly managed

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