Insect pollination is an economically important ecosystem service that depends heavily on wild pollinators. Landscape transformation caused by conversion to agriculture threatens habitats of wild pollinators, reducing their potential to provide ecosystem services. The landscape in Jambi Province, Sumatra, Indonesia, is an example of a region undergoing landscape transformation, from biodiverse natural forests, to intermediate land uses such as fallow shrubland and jungle rubber, to monospecific oil palm plantations. My dissertation explores how transitions between these land uses impact pollinator biodiversity and ecosystem functions and services. I consider different facets of this interface: the impacts of adjacent forest on pollination services to oil palm; mechanisms driving ecosystem functions and services following agroforestry enrichment within oil palm; and landscape-scale comparisons quantifying interacting local and landscape effects on a native pollinator species. My first chapter reviews the state of the knowledge of oil palm pollination by insects. I conducted a systematic review of biotic and abiotic drivers of oil palm pollination and pollinator populations. I present the current understanding of the globally introduced West African Weevil (Elaeidobius kamerunicus), whose regional population fluctuations have negatively impacted yield and resilience, as well as other potential pollinator species endemic to particular growing regions. Based on my review, I describe specific issues concerning biotic, management, and climate drivers of pollination that should be the focus of future oil palm pollination research. In my second chapter, I examine the role that natural habitat can play as a source of pollination ecosystem services and ecological spillover effects in an oil palm field experiment. I compared treatments controlling visitors and pollination of female oil palm inflorescences over a distance gradient from an adjacent forest border. I found that exclusion of all visitors significantly decreased fruit set compared to other treatments, confirming insect pollination is necessary for adequate yield. Forest proximity had a significant positive effect on fruit set when large visitors were excluded. This effect was not significant for treatments that minimized pollinator contributions, suggesting this trend was not due to abiotic factors. However, insect abundances associated with oil palm inflorescences were not strongly related to distance from forest, and only E. kamerunicus had a significant relationship with fruit set. These results could suggest that non-consumptive ecological spillover from forests may influence oil palm pollination, though more experimental work is needed to identify these interactions. In my third chapter, I explore how enriching the oil palm agricultural matrix with up to six tree species played a role in driving insect-mediated ecosystem functions. Within a plantation-scale, long-term oil palm biodiversity enrichment project, I disentangled the direct and indirect effects of enrichment on services (pollination, biocontrol) and disservices (herbivory) using random partition analysis and structural equation models. These models indicate that changes in canopy openness, driven by enrichment treatments, played an important role in ecological patterns at multiple levels of interaction. These had effects on herbivorous insects and pollinators, the latter of which had a positive effect on the fruit production of phytometer plants (Capsicum annuum) placed in the plots. Our results show that, even in early stages of ecological restoration of oil palm, ecosystem functions and services can be affected. These effects are mediated by decreasing canopy openness; however, these relationships may change as enrichment communities continue to develop. In my fourth chapter, I examine the counterbalancing roles of local land use and amount of landscape habitat in pollinator survival and growth, using the native stingless bee Tetragonula laeviceps as a focal species. I established three colonies in 40 plots within Jambi’s transformation landscape, selecting from four predominant habitat types (degraded primary forest, shrubland, rubber plantation, and oil palm plantation) and controlling for a gradient of natural habitat (i.e., forest and shrubland) composition in a 500 m radius. I found that hives with higher local flower species richness had more pollen stores, which in turn was associated with increased bee and colony size. Colonies in structurally complex habitats such as forest and rubber plantations had lower mortality and greater gains in hive size than colonies in open habitats such as oil palm and shrubland; however, open habitats had higher flower species richness and abundance. Open habitats, which are increasing with rainforest conversion, reduce suitable nesting habitat but may increase floral resources in the landscape. Considering the key pollinating function of stingless bees, understanding how this trade-off translates to landscape and population scales will be critical in light of the continued deforestation crisis in the tropics. In summary, understanding and protecting the resources supporting pollination are critical to improving the sustainability of oil palm and can support the livelihoods of people living in the landscape. The impact of habitat loss from agriculture conversion can adversely impact wild pollinator populations through the loss of suitable habitats, as I observed with T. laeviceps, but also changes the flowering resource landscape. In my review of oil palm pollination, I show that a better understanding of biodiversity and landscape drivers of pollination of oil palm itself is needed. My own oil palm field experiment demonstrates how natural habitat and biodiversity may interact positively with oil palm production. I show in my experiments within the oil palm biodiversity enrichment project that tree biodiversity enrichment can indirectly influence pollination services and ecosystem functions, even at an early stage. However, the ecosystem services and disservices affected by ecological restoration will continue to change as the ecological community develops. Our task in future research will be to continue to disentangle these relationships with the aim of recovering or preserving biodiversity and ecosystem function while informing sustainable ecological strategies for farmers and land managers. | 2022-10-04

Necessity of pollinators in ecosystem services and their decline has raised concern for their conservation both in farm lands and urban areas. With the aim of conservation of these pollinators, we initiated developing a pollinator garden at Yelahanka Campus of ICAR-National Bureau of Agricultural Insect Resources in an area of one acre by planting over 50 diverse plant species. Thirty-nine different species of bees were documented from the flora of the pollinator garden. Out of the thirty-nine species of bees, nineteen species of bees belong to non-apis families viz., Megachilidae and Halictidae. Apart from foraging on the flowers, the solitary bees like Megachile sp. were found nesting in the stems, fallen dried flowers in the pollinator garden. The bees were found year-round foraging upon the flora in the pollinator garden. Pollinator garden is a way to in-situ conserve the native bees to sustain the valuable pollination service in various crop plants provided by them.

Population declines of pollinators constitute a major concern for the fate of biodiversity and associated ecosystem services in a context of global change. Massive declines of pollinator populations driven by habitat loss, pollution, and climate change have been reported, whose consequences at community and ecosystem levels remain elusive. We conducted a mathematical modeling and computer simulation study to assess the dynamic consequences of pollinator declines for the biodiversity of plants and pollinators. Specifically, we evaluated the effects of increased mortality and decreased carrying capacity of specialist vs. generalist and effective vs. ineffective pollinators visiting specialist vs. generalist plants on long-term community biomass and species persistence. Our results reveal that increased larval mortality and increased competition for space among larvae had the greatest impacts on the decline of pollinator diversity. In contrast, the largest sustained decreases in pollinator biomass were driven by increased adult mortality in spite of a small increase in pollinator species persistence. Decreased pollinator diversity led in turn to decreased plant diversity. Attacking pollinators with high degree and connected mostly to low-degree plants produced the greatest losses of plant diversity. Pollinator effectiveness had no noticeable effect on persistence. Our results illuminate our understanding of the consequences of pollinator declines for the maintenance of biodiversity. | Fil: Ramos Jiliberto, Rodrigo. Universidad Mayor; Chile | Fil: Moisset de Espanés, Pablo. Centre for Biotechnology and Bioengineering; Chile | Fil: Vazquez, Diego P.. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina

Biodiversity loss affects the functioning of all ecosystems, including agroecosystems, through the loss of essential ecosystem services. Supporting populations of organisms providing those services though vegetation diversification schemes is a promising tool to maintain a high agricultural production as well as ecosystem health. Nevertheless, those schemes show contrasted and unexplained results. This work aims at understanding how increased cultivated diversity impacts pollinator and natural enemy community structure and functioning by considering interactions within and among those groups. Our results show a community shift in response to increased resource diversity, possibly leading to negative interactions. In aphid – parasitoid – hyperparasitoid trophic foodwebs, resource diversification seemed to increase hyperparasitism and competition among primary parasitoids, that could explain the limited aphid control. The intensive use of cultivated flowers by the domestic honeybee seemed to limit wild pollinator use of this resource. Moreover, we highlighted a decrease in aphid parasitism rate in response to high pollinator abundances, suggesting for the first time possible negative interactions among those groups. Rethinking agricultural landscapes considering resource use of each group at different spatio-temporal scales as well as interactions within and among groups is essential to optimize simultaneously several ecosystem services and reach more autonomous and resilient agricultural production. | La crise de la biodiversité affecte le fonctionnement de tous les écosystèmes, notamment agricoles, via une perte des services écosystémiques. Favoriser les populations d’organismes à l’origine de ces services via des stratégies de diversification végétale est un levier prometteur pour maintenir une production agricole élevée ainsi que la santé des écosystèmes, mais les résultats obtenus sont variables et peu expliqués. L’objectif de cette thèse est de comprendre comment l’augmentation de la diversité cultivée impacte la structure et le fonctionnement des communautés de pollinisateurs et d’ennemis naturels en considérant leurs interactions. Nos résultats montrent que la diversification des ressources modifie la composition des communautés, pouvant mener à des interactions négatives. Dans les réseaux trophiques puceron – parasitoïde – hyperparasitoïde, la diversification semble avoir augmenté l’hyperparasitisme et la compétition entre les parasitoïdes primaires, ce qui expliquerait un contrôle des pucerons limité. L’utilisation massive des fleurs cultivées par les abeilles domestiques semble limiter l’utilisation de cette ressource par les pollinisateurs sauvages. De plus, nous avons observé une diminution du service de régulation des pucerons par les parasitoïdes en réponse à une forte abondance de pollinisateurs, signalant pour la première fois de possibles interactions négatives entre ces deux groupes. Optimiser plusieurs services écosystémiques simultanément demande de repenser les paysages agricoles en considérant l’utilisation des ressources de chaque groupe d’organismes à différentes échelles spatio-temporelles ainsi que les interactions au sein et entre ces groupes.

Pollinators provide crucial ecosystem services that underpin to wild plant reproduction and yields of insect-pollinated crops. Understanding the relative impacts of anthropogenic pressures and climate on the structure of plant–pollinator interaction networks is vital considering ongoing global change and pollinator decline. Our ability to predict the consequences of global change for pollinator assemblages worldwide requires global syntheses, but these analytical approaches may be hindered by variable methods among studies that either invalidate comparisons or mask biological phenomena. Here we conducted a synthetic analysis that assesses the relative impact of anthropogenic pressures and climatic variability, and accounts for heterogeneity in sampling methodology to reveal network responses at the global scale. We analyzed an extensive dataset, comprising 295 networks over 123 locations all over the world, and reporting over 50,000 interactions between flowering plant species and theirinsect visitors. Our study revealed that anthropogenic pressures correlate with an increase in generalism in pollination networks while pollinator richness and taxonomic composition are more related to climatic variables with an increase in dipteran pollinator richness associated with cooler temperatures. The contrasting response of species richness and generalism of the plant–pollinator networks stresses the importance ofconsidering interaction network structure alongside diversity in ecological monitoring. In addition, differences in sampling design explained more variation than anthropogenic pressures or climate on both pollination networks richness and generalism, highlighting the crucial need to report and incorporate sampling design in macroecological comparative studies of pollination networks. As a whole, our study reveals a potential human impact on pollination networks at a global scale. However, further research is needed to evaluate potential consequences of loss of specialist species and their unique ecological interactions and evolutionary pathways on the ecosystem pollination function at a global scale.

International audience | 1. In agricultural landscapes, arthropods provide essential ecosystem services such as biological pest control and pollination. Intensified crop management practices and homogenization of landscapes have led to declines among such organisms. Semi-natural habitats, associated with high numbers of these organisms, are increasingly lost from agricultural landscapes but diversification by increasing crop diversity has been proposed as a way to reverse observed arthropod declines and thus restore ecosystem services. However, whether or not an increase in the diversity of crop types within a landscape promotes diversity and abundances of pollinating and predaceous arthropods, and how semi-natural habitats might modify this relationship, are not well understood. 2. To test how crop diversity and the proportion of semi-natural habitats within a landscape are related to the diversity and abundance of beneficial arthropod communities , we collected primary data from seven studies focusing on natural enemies (carabids and spiders) and pollinators (bees and hoverflies) from 154 crop fields in Southern Sweden between 2007 and 2017. 3. Crop diversity within a 1-km radius around each field was positively related to the Shannon diversity index of carabid and pollinator communities in landscapes rich in semi-natural habitats. Abundances were mainly affected by the proportion of semi-natural habitats in the landscape, with decreasing carabid and increasing pollinator numbers as the proportion of this habitat type increased. Spiders showed no response to either crop diversity or the proportion of semi-natural habitats.

Conservation practices in agriculture—such as biological pest control, provision of pollinator habitat and cover cropping—may provide ecosystem services that are beneficial to both farmers and wildlife. Despite these benefits, however, their use is not yet widespread and the factors that may limit adoption are not well-understood. In this study we tested potential associations between farmers' beliefs about ecosystem services and their management practices using data collected from questionnaires and cognitive maps from 31 Michigan blueberry and cherry farmers describing their farming systems. We found that farmers who included key biological pest control concepts in their mental model representations reported the use of more conservation practices, and/or participation in conservation programs, than those who did not. In addition, the timing of management practices was a more central factor in the mental models of farmers who included both natural predators and beneficial insects than those omitting these factors. Finally, the farmers who included those two factors showed higher degrees of systems thinking based on mental model metric analysis. We suggest that outreach emphasizing the relationships between ecosystem services and the factors farmers view as most important may positively influence communication and potential of adoption of conservation practices and preventative pest management strategies.

1. In agricultural landscapes, arthropods provide essential ecosystem services such as biological pest control and pollination. Intensified crop management practices and homogenization of landscapes have led to declines among such organisms. Semi-natural habitats, associated with high numbers of these organisms, are increasingly lost from agricultural landscapes but diversification by increasing crop diversity has been proposed as a way to reverse observed arthropod declines and thus restore ecosystem services. However, whether or not an increase in the diversity of crop types within a landscape promotes diversity and abundances of pollinating and predaceous arthropods, and how semi-natural habitats might modify this relationship, are not well understood. 2. To test how crop diversity and the proportion of semi-natural habitats within a landscape are related to the diversity and abundance of beneficial arthropod communities, we collected primary data from seven studies focusing on natural enemies (carabids and spiders) and pollinators (bees and hoverflies) from 154 crop fields in Southern Sweden between 2007 and 2017. 3. Crop diversity within a 1-km radius around each field was positively related to the Shannon diversity index of carabid and pollinator communities in landscapes rich in semi-natural habitats. Abundances were mainly affected by the proportion of semi-natural habitats in the landscape, with decreasing carabid and increasing pollinator numbers as the proportion of this habitat type increased. Spiders showed no response to either crop diversity or the proportion of semi-natural habitats. Synthesis and applications. We show that the joint effort of preserving semi-natural habitats and promoting crop diversity in agricultural landscapes is necessary to enhance communities of natural enemies and pollinators. Our results suggest that increasing the diversity of crop types can contribute to the conservation of service-providing arthropod communities, particularly if the diversification of crops targets complex landscapes with a high proportion of semi-natural habitats. KEYWORDS agricultural intensification, arable land, crop diversity, diversification, ecosystem services, landscape composition, pollination, predation

Insect pollination is a globally important ecosystem service, contributing to crop yields, production stability and the maintenance of wild plant populations. Ironically, agriculture is one of the major global drivers of wild insect pollinator decline. At the same time, increasing human population is driving ever greater demands on crop production. Agroforestry (AF) – a more diverse farming system integrating woody and agricultural crops – can theoretically reconcile high production with provision of ecosystem services such as pollination. However, empirical studies of pollination in temperate AF systems are almost entirely lacking. We sought to fill this knowledge gap by assessing whether AF can provide increased pollination service compared to monoculture (MC) systems. Six UK sites, each containing an AF and a MC system, were studied over three years. Wild pollinator abundance and diversity were used as proxies for the magnitude and stability, respectively, of the pollinating community. We also directly measured pollination service as seed set in a wild plant phytometer. We found that temperate AF systems can provide greater pollination service than MC: AF treatments had twice as many solitary bees and hoverflies, and in arable systems 2.4 times more bumblebees, than MC treatments. AF also had 4.5 times more seed set compared to MC in one of the two years. At 40% of site-by-year sampling units, species richness of solitary bees was on average 10.5 times higher in AF treatments. This provides evidence in favour of the expectation that AF systems can support higher pollinator richness, and therefore greater potential stability, of pollination service. For the other sampling units, and for bumblebees (Bombus spp.), there was no treatment effect on species richness. Further work is needed to investigate the effect of AF on species richness and its mechanistic basis. Our results also highlight the importance of AF system design, ensuring that ecosystem services outcomes are explicitly planned at the design stage. We suggest that AF has a role to play in improving the sustainability of modern farming and in mitigating the ongoing loss of wild pollinating insects, which is strongly driven by prevailing agricultural practices.