Cacao flower visitation: Low pollen deposition, low fruit set and dominance of herbivores

Pollination services of cacao are crucial for global chocolate production, yet remain critically understudied, particularly in regions of origin of the species. Notably, uncertainties remain concerning the identity of cacao pollinators, the influence of landscape (forest distance) and management (shade cover) on flower visitation and the role of pollen deposition in limiting fruit set. Here, we aimed to improve understanding of cacao pollination by studying limiting factors of fruit set in Peru, part of the centre of origin of cacao. Flower visitors were sampled with sticky insect glue in 20 cacao agroforests in two biogeographically distinct regions of Peru, across gradients of shade cover and forest distance. Further, we assessed pollen quantities and compared fruit set between naturally and manually pollinated flowers. The most abundant flower visitors were aphids, ants and thrips in the north and thrips, midges and parasitoid wasps in the south of Peru. We present some evidence of increasing visitation rates from medium to high shade (40%–95% canopy closure) in the dry north, and opposite patterns in the semi-humid south, during the wet season. Natural pollination resulted in remarkably low fruit set rates (2%), and very low pollen deposition. After hand pollination, fruit set more than tripled (7%), but was still low. The diversity and high relative abundances of herbivore flower visitors limit our ability to draw conclusions on the functional role of different flower visitors. The remarkably low fruit set of naturally and even hand pollinated flowers indicates that other unaddressed factors limit cacao fruit production. Such factors could be, amongst others, a lack of effective pollinators, genetic incompatibility or resource limitation. Revealing efficient pollinator species and other causes of low fruit set rates is therefore key to establish location-specific management strategies and develop high yielding native cacao agroforestry systems in regions of origin of cacao. © 2022 The Authors. Ecological Solutions and Evidence published by John Wiley & Sons Ltd on behalf of British Ecological Society

Birds and bats enhance cacao yield despite suppressing arthropod mesopredation

Bird- and bat-mediated biocontrol benefits the productivity of tropicalcommodity crops such as cacao, but the ecological interactions drivingthese ecosystem services remain poorly understood. Whereas birds and batsprey on herbivorous arthropods, they may also prey on arthropodmesopredators such as ants, with poorly understood consequences for pestbiocontrol. We used a full-factorial experiment excluding birds, bats, andants to assess their effects on (a) the abundanceof multiple arthropodgroups; (b) predation pressure on arthropods evaluated through artificialsentinel caterpillars; and (c) cacao yield over 1 year in shaded agroforestrysystems of native cacao varieties in Peru. Birds and bats increasedcacao yield by 118%, which translates in smallholder benefits of ca.US $959 ha−1year−1. Birds and bats decreased predation by ants and otherarthropods, but contributed to thecontrol of phytophagous taxa such asaphids and mealybugs. By contrast, ant presence increased the abundanceof these sap-sucking insects, with negative impacts for cacao yield.Notably, high abundances of the dominant antNylanderiasp., known toattend sap-sucking insects, were associated with lower cacao yield along adistance gradient from the closest forest edge. According to these results,arthropod predation by birds and bats, rather than mesopredation byarthropods, was most responsible forincreases in cacao yield. Moving for-ward, detailed research about their trophic interactions will be necessary toidentify the cause of such benefits. Retaining and restoring the large bene-fits of birds and bats as well as minimizing disservices by other taxa incacao agroforests can benefit from management schemes that prioritizepreservation of shade trees and adjacent forests within agroforestrylandscapes

Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes

Animals provide services such as pollination and pest control in cacao agro- forestry systems, but also disservices. Yet, their combined contributions to crop yield and fruit loss are mostly unclear. In a full-factorial field exper- iment in northwestern Peru, we excluded flying insects, ants, birds and bats from cacao trees and assessed several productivity indicators. We quan- tified the contribution of each group to fruit set, fruit loss and marketable yield and evaluated how forest distance and canopy closure affected pro- ductivity. Fruit set dropped (from 1.7% to 0.3%) when flying insects were excluded and tripled at intermediate (40%) compared to high (greater than 80%) canopy cover in the non-exclusion treatment. Fruit set also dropped with bird and bat exclusion, potentially due to increased abundances of arthropods preying on pollinators or flower herbivores. Overall, cacao yields more than doubled when birds and bats had access to trees. Ants were generally associated with fruit loss, but also with yield increases in agroforests close to forest. We also evidenced disservices generated by squir- rels, leading to significant fruit losses. Our findings show that several functional groups contribute to high cacao yield, while trade-offs between services and disservices need to be integrated in local and landscape-scale sustainable cacao agroforestry managemen

Cacao flower visitation: Low pollen deposition, low fruit set and dominance of herbivores

Pollination services of cacao are crucial for global chocolate production, yet remain critically understudied, particularly in regions of origin of the species. Notably, uncertainties remain concerning the identity of cacao pollinators, the influence of landscape (forest distance) and management (shade cover) on flower visitation and the role of pollen deposition in limiting fruit set. Here, we aimed to improve understanding of cacao pollination by studying limiting factors of fruit set in Peru, part of the centre of origin of cacao. Flower visitors were sampled with sticky insect glue in 20 cacao agroforests in two biogeographically distinct regions of Peru, across gradients of shade cover and forest distance. Further, we assessed pollen quantities and compared fruit set between naturally and manually pollinated flowers. The most abundant flower visitors were aphids, ants and thrips in the north and thrips, midges and parasitoid wasps in the south of Peru. We present some evidence of increasing visitation rates from medium to high shade (40%–95% canopy closure) in the dry north, and opposite patterns in the semi-humid south, during the wet season. Natural pollination resulted in remarkably low fruit set rates (2%), and very low pollen deposition. After hand pollination, fruit set more than tripled (7%), but was still low. The diversity and high relative abundances of herbivore flower visitors limit our ability to draw conclusions on the functional role of different flower visitors. The remarkably low fruit set of naturally and even hand pollinated flowers indicates that other unaddressed factors limit cacao fruit production. Such factors could be, amongst others, a lack of effective pollinators, genetic incompatibility or resource limitation. Revealing efficient pollinator species and other causes of low fruit set rates is therefore key to establish location-specific management strategies and develop high yielding native cacao agroforestry systems in regions of origin of cacao