Ecological, environmental, and management data indicate apple production is driven by wild bee diversity and management practices

Climate, landscape composition, management practice, and wild bee pollination are all variables thought to play significant roles in commercial apple production. However, how these variables affect production efficiency under field-realistic conditions has not been investigated at large geographical scales. We combined intensive standardized field surveys (using netting and pan traps) with structural equation models to explore the relative impact of biotic and abiotic variables on bee diversity, apple yield and fruit quality, and their ability to represent reliable proxies of apple production. Here we show that apple yields are mainly driven by management practice, without evidence for a significantly superior contribution by managed honey bees. Total wild bee diversity, while negatively correlated with honey bee dominance, promoted apple quality by enhancing seed set number. Our study demonstrates that even across a broad geographical range there is potential to harness wild bee diversity as nature-based solution and as a substitute to an exclusive reliance on honey bees in the context of commercial apple production

CropPol: a dynamic, open and global database on crop pollination

Seventy five percent of the world's food crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop yield, as well as to anticipate changes in this service, develop predictions, and inform management actions. Here, we present CropPol, a dynamic, open and global database on crop pollination. It contains measurements recorded from 202 crop studies, covering 3,394 field observations, 2,552 yield measurements (i.e. berry weight, number of fruits and kg per hectare, among others), and 47,752 insect records from 48 commercial crops distributed around the globe. CropPol comprises 32 of the 87 leading global crops and commodities that are pollinator dependent. Malus domestica is the most represented crop (32 studies), followed by Brassica napus (22 studies), Vaccinium corymbosum (13 studies), and Citrullus lanatus (12 studies). The most abundant pollinator guilds recorded are honey bees (34.22% counts), bumblebees (19.19%), flies other than Syrphidae and Bombyliidae (13.18%), other wild bees (13.13%), beetles (10.97%), Syrphidae (4.87%), and Bombyliidae (0.05%). Locations comprise 34 countries distributed among Europe (76 studies), Northern America (60), Latin America and the Caribbean (29), Asia (20), Oceania (10), and Africa (7). Sampling spans three decades and is concentrated on 2001-05 (21 studies), 2006-10 (40), 2011-15 (88), and 2016-20 (50). This is the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date, and we encourage researchers to add more datasets to this database in the future. This data set is released for non-commercial use only. Credits should be given to this paper (i.e., proper citation), and the products generated with this database should be shared under the same license terms (CC BY-NC-SA). This article is protected by copyright. All rights reserved

Wild bees and decline factors: a standardized study of human-modified contexts

The diversity of organisms within an ecosystem is essential to its functioning. It ensures a stable provision of goods and services, along with the resilience of many communities facing disturbances. Pollinators are involved in the reproduction cycle of a vast majority of flowering plants and crops, and play an essential role in overall ecosystem functioning. Wild bees constitute the most important group of pollinators worldwide. However, this major role is currently under threat with recent reports describing a global decline of overall communities. There are many different factors involved in these declines, both biotic and abiotic, many of which are induced by human activities and act either isolated or in combination with other factors. Climate, landscape and local factors are the main drivers of bee decline. They tend to influence one another, with synergistic effects also influencing bees in different ways. Many experts are calling for meaningful conservation measures to avoid massive detrimental consequences of multi-stressor interactions on wild bee communities inevitably leading to weakened ecosystem functioning.In regard to the complex interactions between decline factors in the context of human-induced global change, and the central pillar of biodiversity that wild bees represent, this thesis focuses our attention on an in-depth exploration of these intricate links. More specifically, our main objective is to study the relative impacts of decline factors in shaping wild bee communities, at different geographic scales and in different human-modified landscapes. We aimed to (i) disentangle the effects of intertwined factors in different contexts, in order to (ii) question long-held beliefs, and finally (iii) find key drivers for future conservation of wild bee communities.To achieve these aims, we decided to investigate both at a continental (i.e. one crop) and a local scale (i.e. one city). We observed standardized sampling methods to collect data on wild bee species combining active samplings using entomological nets during transect walks and passive samplings using colored pan traps. We also used historical data to characterize the bee fauna of a specific urban green space. This data allowed us to characterize wild bee communities at different scales by computing the species richness, functional and phylogenetic diversity. We then extracted data on decline factors such as climate, landscape composition and local factors using existing public databases and analyzing pollen samples. The relative effects of decline factors on wild bee communities were explored by using regression techniques, more specifically by building generalized linear models and structural equation models.The first chapter is a broad introduction on the global ecological background necessary to appreciate our research, followed by an explanation of the scope and corresponding outline of the thesis. Secondly, we give a general overview of the methodology used to collect the different types of data, the metrics chosen to characterize this data, and the statistical tools employed to answer our main objectives. The three formulated aims of this thesis are then explored throughout four main chapters (3 to 6), each of which represents an independent scientific study with distinct research questions, and all progressively answering our main objective. The seventh chapter is a large discussion developing the general relevance of this thesis, along with future perspectives for wild bee and overall biodiversity conservation, also including leads for future research. Finally, a general conclusion is given in chapter 8.In chapter 3, we use generalized linear models (GLMs) to disentangle the effects of local factors (i.e. land cover, management practices and honey bee dominance) on overall wild bee diversity. More specifically, we used standardized field surveys to sample bee specimens in 36 commercial apple orchards (paired in organic and non-organic) in Western Europe during the 2019 flowering season. Considering simultaneously all these parameters, the presence of managed honey bees in the apple orchards appeared to be the main factor influencing all wild bee diversity metrics, far beyond climate and landscape variables. Our results also show that organic practices in commercial apple orchards, believed to be highly beneficial to wild pollinator communities, actually constitute mere substitutes of conventional practices, with no measured benefits on overall wild bee diversity.Chapter 4 builds on the previous one, by including supplementary aspects of apple production and pollination efficiency. Here, we explore the causal and embedded effects of multiple biotic and abiotic stressors of wild bees (i.e. climate, landscape, management practices and local factors) on overall wild bee diversity. We also studied the effects on apple crop yield and fruit set using piecewise structural equation models (pSEM). Building on the dataset used in Chapter 3, we extend our scope to reach a total of 46 commercial apple orchards (organic and non-organic) in Western Europe and Morocco, sampled during the 2019 flowering season. Additionally, we collected data on crop yield and fruit quality following the same 2019 flowering season to explore aspects of pollination efficiency. The results presented here show that apple yields are mainly driven by management practice, without evidence for a significantly superior contribution by managed honey bees. Total wild bee diversity, while negatively correlated with honey bee dominance, enhanced seed set.The articles presented in Appendix E and F represent parallel published studies, going deeper in the description of methods used to (i) measure bee diversity, and (ii) to survey bee communities along a large-scale climatic gradient. These two parallel studies underline the relevance of the standardized survey methods and the diversity metrics used in chapter 3 and 4. The bee sampling data collected was shared with fellow scientists to help build what is now the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date, presented in Appendix G. Together, chapter 3 and 4 constitute the aspect of this thesis focusing essentially on a human- modified context at a large geographic scale.In chapter 5, we explore an entirely different human-modified context, focusing on the drivers of wild bee diversity at the local scale and in an urban environment. We use an innovative experimental setup to explore the role of urbanization in the distribution of different wild bee decline factors. More specifically, for 50 sites within the Brussels-Capital region, we used pollen samples collected by solitary females of two Osmia species as bioindicators of plant richness, pesticide residues and parasite load. We then computed GLM to disentangle the prevalence of these drivers along an urbanization gradient. Overall, our results from chapter 5 showed that urbanization in itself did not act as an environmental filter of decline factors, neither on host plants availability.Building on the previous findings, chapter 6 is a case study showing how a certain habitat type present within urban areas (i.e. urban wastelands) can constitute a refuge to wild bee species. We compile five years of citizen science and standardized field surveys to characterize the wild bee community of the Friche Josaphat, the largest urban wasteland in the Brussels-Capital Region. We then use diversity metrics to compare the species at our target site with the regional list of species, and use null models of community assembly to test the local species assemblages against random assemblages. Our results show a significant share of the functional and phylogenetic diversity of wild bees known from the Brussels-Capital Region is represented in the Friche Josaphat, making it one of the most species-rich localities known to date for wild bees in Belgium. We highlight the strong complementarity of citizen science and academic approaches in biodiversity surveys. We also reaffirm the potential of wastelands as essential components of urban biodiversity. This chapter further addresses the long-held belief that urbanization is bad for wild bee communities, by putting the accent on the complex mosaic of habitats represented in urban areas, with high associated potential for future conservation measures.Overall, our results show that interactions between wild bee species and their environmental living conditions are an extremely complex and dynamic phenomenon, largely depending on local conditions that differ according to the spatial scale considered. On one hand, we investigated the wild bee communities associated to one of the most widespread crops in the world, at a continental scale and using standardized sampling methods in a way that had never been done before on such a large climate gradient and all within the same flowering season. On the other hand, we designed a truly innovative experimental setup to explore stressors of wild bee communities found at a local scale within one of the greenest cities in Europe. We also show that using standardized sampling methods in real life conditions is crucial for comparisons between studies from different landscapes and to build consistent long-term monitoring of species.Finally, this thesis opens clear doors for future research. While our research focused on apple orchards, we think that modeling contrasting crops could be interesting to provide a more balanced insight on the main drivers of bee diversity at different spatial and phenological scales. We strongly suggest that coming studies use standardized methods to monitor overall wild bee communities for multiple flowering seasons and use that data to model temporal trends of the relative impact of decline factors for wild bees. We also believe that significant improvements of our models can be made by increasing the amount of data collected, in turn feeding and refining the causal models. Regarding the experimental setup developed in chapter 5, we think it should be seen as a cheap, efficient and logistically practical tool. It will allow to broadly monitor the environmental composition in elements strongly shaping pollinator communities at the local level and good for all landscape contexts. We suggest that future studies willing to reproduce similar types of monitoring use this tool and improve it.Doctorat en Sciences agronomiques et ingénierie biologiqueinfo:eu-repo/semantics/nonPublishe

Five years of citizen science and standardised field surveys in an informal urban green space reveal a threatened Eden for wild bees in Brussels, Belgium

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Dominance of honey bees is negatively associated with wild bee diversity in commercial apple orchards regardless of management practices

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Insect biomass is not a consistent proxy for biodiversity metrics in wild bees

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Potential for climate change driven spatial mismatches between apple crops and their wild bee pollinators at a continental scale

peer reviewedVisitation by wild bee species alongside managed pollinators is necessary to ensure consistent yields and fruit quality in apple fields. Wild bee species are vulnerable to several environmental changes. Climate change is expected to lead to broad-scale changes to wild bee distributions that will impact the service they provide as crop pollinators. We modelled selected wild bee species known to be important for apple production in Europe and we quantified the shifts in distribution range for these key apple-pollinating bee species (KABS) under three climate‌ change scenarios (RCP 2.6, 4.5 and 8.5) for 2041–2060 and 2061–2080. We compared species distribution maps (after the expected range changes) to the distribution of areas with suitable habitat for apple orchards and with national apple production statistics to estimate potential pollination service at the landscape scale. Overall, ‌KABS are widespread species found across Europe and while most species have projected range contractions, these contractions are limited (∼10% loss). Only under the worst-case climate change scenario (RCP8.5) do we project range contractions over 50% and only under RCP8.5 is the average loss of overlap between suitable apple conditions and KABS likely to decrease by over 10%. However, range contractions at the southern limit of many species’ ranges mean that the potential impact of climate change on apple pollination is not evenly shared between apple producing countries; France and Italy for example are projected to have high range loss of KABS and loss in potential pollination service. Climate change is not the only threat to apple pollination and future pollination deficits will also depend on local orchard intensification and ecological infrastructure. Key changes to intensive, commercial apple orchards towards a more agroecological approach are needed to maintain a diverse wild bee community and apple production in areas that may become climatically unsuitable in the future

European bee diversity: taxonomic and phylogenetic patterns

Aim Wild bees still face striking shortfalls in knowledge of biodiversity in key regions of the world. This includes Europe, where despite a long tradition of data gathering, the continental scale distribution patterns of wild bees have not been systematically analysed to date. This study aims to characterise large-scale biodiversity patterns to: (i) understand spatial–temporal heterogeneity in large-scale databases, (ii) locate genuine diversity hotspots and their relationship with biogeographical patterns or habitats of interests and (iii) identify understudied species and areas to further design conservation actions for most at risk species in key regions. Location Europe. Taxon Bees. Methods We present a continental and standardised study of bee taxonomic and phylogenetic diversity patterns in Europe, using a large compilation of occurrence records of nearly three million validated occurrence records for 1515 wild bee species. Results Southern and eastern Europe suffer from the largest gaps in data availability while northern and western regions benefit from better historical coverage. Our models show that higher wild bee diversity in Europe is hosted in xeric, warm areas, as highlighted by a clear latitudinal gradient. However, phylogenetic diversity is predicted to be more homogenous across Europe than taxonomic diversity, suggesting that policies and strategies targeted to protect species richness may differ from those targeting greater phylogenetic diversity. Main conclusions This study represents a significant advance in the characterisation of wild bee distribution patterns across Europe and is an important stepping stone towards the design of more targeted survey efforts and conservation actions of this key group of pollinators. This, in turn, will provide the data necessary to improve the spatiotemporal coverage in a context of ongoing and future Europe-wide monitoring schemes, to ultimately develop cost-effective, coordinated and evidence-based conservation actions and tailored habitat management actions that can be implemented on a smaller scale

A comparative analysis of crop pollinator survey methods along a large-scale climatic gradient

Safeguarding crop pollination services requires the identification of the pollinator species involved and the provision of their ecological requirements at multiple spatial scales. However, the potential for agroecological intensification of pollinator-dependent crops by harnessing pollinator diversity is limited by our capacity to characterise the community of pollinator species for each crop, and to determine how it is influenced by the different survey methods used, as well as by climatic variables at larger geographic scales. Here, we surveyed wild bees using a standardised protocol at an unprecedented scale including 62 commercial apple orchards in Western and Central Europe (i) to validate recent findings on pollinator community divergence as measured by common survey methods (netting and pan trapping) using conventional and alternative biodiversity metrics (phylogenetic and functional diversity), and (ii) to investigate the impact of climatic variation on the patterns observed. Our results confirm the significant divergence in pollinator communities measured using the two common methods at the larger, sub-continental scale, and we provide evidence for a significant influence of climate on the magnitude of pollinator community divergence (beta diversity and its turnover component) between survey methods, particularly when comparing colder to warmer sites and regions. We also found that warmer sites are more dissimilar than colder sites in terms of species composition, functional traits, or phylogenetic affinities. This result probably stems from the comparatively larger species pool in Southern Europe and because apple flowers are accessible to a wide spectrum of pollinator species; hence, two distant survey localities in Southern Europe are more likely to differ significantly in their pollinator community. Collectively, our results demonstrate the spatially-varying patterns of pollinator communities associated with common survey methods along a climate gradient and at the sub-continental scale in Europe.SCOPUS: ar.jinfo:eu-repo/semantics/publishe