Contrasting effects of habitat management on different feeding guilds of herbivorous insects in cacao agroforestry systems

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 traditional cacao agroforests, known as “cabrucas,” on the conservation of the herbivorous insect community in compared with that of monodominant rubber agroforests. The insects were sampled in three habitats in southeastern Bahia, Brazil: native forests, cabrucas and rubber agroforests. In each habitat, 18 plots of 10 m<sup>2 </sup>were established, and the structural measures were collected and herbivorous insects were sampled with a Malaise/window trap. The diversity of folivores 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 limits 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 cabruca 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 with that of the 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 conclude that cabrucas have 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 with the rubber agroforests. We also emphasize the potential risk of local pest outbreaks in rubber agroforests for both the rubber trees and associated cacao tress.

Spatio-Temporal Distribution of Bark and Ambrosia Beetles in a Brazilian Tropical Dry Forest

“…We collected beetles using combined flight Malaise/window traps ( Basset 1988 , Novais et al. 2016 ).…”

A Subcontinental Analysis of Forest Fragmentation Effects on Insect and Disease Invasion

“…They attributed the differences to habitat specificity requirements of guild members [23]. Similarly, Novais et al (2016) found differences in the effect of canopy cover on different insect guilds, with percent canopy cover being positively associated with the richness of leaf-feeding insects, and negatively associated with the richness of sap-feeding insects, and with no significant relation to wood-boring insect richness [29]. These relationships, they concluded, depended in large part on the specific characteristics of the tropical agroforestry system they were studying and of the insect species present.…”

“…(3) predation risk on pests associated with certain predators and their abundance at different edges (including the "natural enemies hypothesis" prediction that higher plant diversity systems support more insect predators that more effectively control herbivore populations [29,33]), and (4) pest ecophysiological and life-history traits that are associated with ecological features and physical positions (i.e., forest layers) at forest edges [34].…”

Positive effects of the catastrophic Hurricane Patricia on insect communities

“…We collected the insects using combined flight Malaise/window traps (Fig. 3B 50 , 66 ). With an exception, one trap per plot (9 total) holding two vial collectors with 70% ethanol were exposed for five days (120 h) in the canopy of the same tree during all sampling periods, at a height ranging from 4 to 7 m in the center of each plot.…”