The effects of urbanisation on pollinators and pollination: A meta-analysis
June 22, 2023
Urbanisation is increasing worldwide, with major impacts on biodiversity, species interactions and ecosystem functioning. Pollination is an ecosystem function vital for terrestrial ecosystems and food security; however, the processes underlying the patterns of pollinator diversity and the ecosystem services they provide in cities have seldom been quantified. Here, we perform a comprehensive meta-analysis of 133 studies examining the effects of urbanisation on pollinators and pollination..
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Bumble bee colony health and performance vary widely across the urban ecosystem
August 17, 2022
Urbanisation is a global phenomenon that can affect fitness and could challenge the persistence of most species, including wild bee pollinators. Yet, how and which environmental features affect bee health and fitness within the urban ecosystem remain unclear. Here, we placed experimental Bombus terrestris colonies in sites spanning from the edge into a city’s core to investigate bumble bee parasitism, foraging behaviour, energetic stress, colony growth and reproductive output. In each site, ambient temperature was recorded, the availability of floral resources was evaluated and landscape heterogeneity was characterized using land-cover maps.
The effects of urbanisation on ecological interactions
April 30, 2022
Cities are expanding worldwide and urbanisation is considered a global threat to biodiversity. Urban ecology has provided important insights on how urban environmental changes might affect individuals, populations and species; however, we know little about how the ecological impacts of urbanisation alter species interactions. Species interactions are the backbone of ecological communities and play a crucial role in population and community dynamics and in the generation, maintenance and structure of biodiversity. Here, I review urban ecological studies to identify key mechanistic pathways through which urban environmental processes could alter antagonistic and mutualistic interactions among species.
Low toxicity crop fungicide (fenbuconazole) impacts reproductive male quality signals leading to a reduction of mating success in a wild solitary bee
April 27, 2022
Recent reports on bee health suggest that sublethal doses of pesticides have negative effects on wild bee reproduction and ultimately on their population growth. Females of the solitary horned mason bee Osmia cornuta, evaluate thoracic vibrations and odours of males to assess male quality. When certain criteria are met, the female accepts the male and copulates. However, these signals were found to be modified by sublethal doses of pesticides in other hymenopterans. Here, we tested whether sublethal doses of a commonly used fungicide (Fenbuconazole) impact male quality signals and mating success in O. cornuta.
Global urban environmental change drives adaptation in white clover
March 20, 2022
Urbanization transforms environments in ways that alter biological evolution. In this study we examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale.
Apple pollination is ensured by wild bees when honey bees are drawn away from orchards by a mass co-flowering crop, oilseed rape
April 27, 2021
Over the past two decades, the cultivated area of oilseed rape, a mass-flowering crop, has markedly increased in Europe in response to bioenergy demands. As well as representing a major shift in floral composition across the landscape, mass-flowering oilseed rape may alter pollination services to other simultaneously blooming crops, either decreasing pollination via competition for pollinators or facilitating it via pollinator spill-over. Apple is an economically important, obligately insect-pollinated fruit crop that co-flowers with oilseed rape. Here using apple orchards that vary in the percentage of oilseed rape in the surrounding landscape, we investigated the effect of oilseed rape on pollinators and pollination of co-blooming apple.
Urban fragmentation leads to lower floral diversity, with knock-on impacts on bee biodiversity
December 10, 2020
Bees and flowering plants are two closely interacting groups of organisms. Habitat loss and fragmentation associated with urbanisation are major threats to both partners. Yet how and why bee and floral richness and diversity co-vary within the urban landscape remain unclear. Here, we sampled bees and flowering plants in urban green spaces to investigate how bee and flowering plant species richness, their phylogenetic diversity and pollination-relevant functional trait diversity influence each other in response to urban fragmentation.
A two-part modelling approach reveals a positive effect of pollinator biodiversity in boosting the pollination of apple flowers
October 26, 2020
Pollinator biodiversity may benefit crop pollination. Yet benefits in agro-ecosystems may be context-dependent and offset by agronomic or other limiting orchard-specific or tree-specific factors that obscure biodiversity-ecosystem service relationships. To test if crop pollination benefitted from pollinator biodiversity, we sampled local wild bee communities in five organic and five Integrated Pest Management (IPM) apple orchards in Germany and experimentally measured the pollination success of apple flowers, quantified as the number of pollen tubes reaching the base of styles. Using a statistical two-part hurdle model which allowed us to separate (i) the probability of pollination and (ii) the quantity of pollination, we were able to demonstrate that the collective effects of local tree/orchard factors acted as a primary limiting threshold for pollination success.
Urbanisation is associated with shifts in bumblebee body size, with cascading effects on pollination
August 08, 2020
Urbanisation is a global phenomenon with major effects on species, the structure of community functional traits and ecological interactions. Body size is a key species trait linked to metabolism, life‐history and dispersal as well as a major determinant of ecological networks. Here, using a well‐replicated urban‐rural sampling design in Central Europe, we investigate the direction of change of body size in response to urbanisation in three common bumblebee species, Bombus lapidarius, Bombus pascuorum and Bombus terrestris, and potential knock‐on effects on pollination service provision.
Disentangling the effects of local resources, landscape heterogeneity and climatic seasonality on bee diversity and plant‑pollinator networks in tropical highlands
July 28, 2020
Land-use alteration and climate seasonality have profound effects on bee species diversity by influencing the availability of nesting and floral resources. Here, using twelve sites embedded in an agriculture–forest mosaic in the tropical highlands of Guatemala, we investigated the relative effects of climate seasonality and landscape heterogeneity on bee and floral-resource community structure and on their mutualistic network architecture.
Urban areas as hotspots for bees and pollination but not a panacea for all insects
January 29, 2020
Urbanisation is an important global driver of biodiversity change, negatively impacting some species groups whilst providing opportunities for others. Yet its impact on ecosystem services is poorly investigated. Here, using a replicated experimental design, we test how Central European cities impact flying insects and the ecosystem service of pollination.
Should I stay or should I go?
August 14, 2019
Plant-pollinator-interactions are often highly specialised and may even lead to coevolution. Yet when plants and pollinators coevolve, it is not clear if this will also result in frequent cospeciation. Here we investigate the mutual evolutionary history of South African oil-collecting Rediviva bees and their Diascia host plants, in which the elongated forelegs of female Rediviva have been suggested to coevolve with the oil-producing spurs of their Diascia hosts using co-phylogenetics. Overall, we show that, even in systems widely believed to be coevolving, pollinator shifts seem to be the dominant diversification process rather than cospeciation, and the few cospeciation events detected are rather due to phylogenetic tracking than coevolution.
A roadmap for urban evolutionary ecology
October 12, 2018
Urban ecosystems are rapidly increasing, but how this affects the evolutionary ecology of species living in urban areas remains largely unknown. Urban ecology has advanced our understanding of how the development of cities and towns changes environmental conditions and alters ecological processes and patterns. However, despite decades of research in urban ecology, the extent to which urbanization influences evolutionary and eco-evolutionary change has received little attention. This Perspective article provides a roadmap for understanding the interplay between ecology and evolution of urban-dwelling organisms. We begin with a brief history of the fields of urban ecology and urban evolution, followed by synthesizing the major themes and recent research in urban evolutionary ecology. We then identify five major knowledge gaps that, if addressed, would significantly
increase our understanding of how urbanization influences both adaptive and non-adaptive evolutionary processes. Lastly, we highlight the importance of integrating urban evolutionary ecology into conservation practice, urban planning, and public engagement.
Genome-wide single nucleotide polymorphism scan suggests adaptation to urbanization in an important pollinator, the red-tailed bumblebee (Bombus lapidarius L.)
April 18, 2018
Urbanization is considered a global threat to biodiversity and a driver of evolutionary change. Here, using 110 314 single nucleotide polymorphisms generated by restriction-site-associated DNA sequencing, we investigated the genome-wide effects of urbanization on putative neutral and adaptive genomic diversity in a major insect pollinator, Bombus lapidarius, collected from nine German cities and nine paired rural sites.Overall, our results provide evidence of local adaptation to urbanization in the face of gene flow in a highly mobile insect pollinator.
Sweat bees on hot chillies: provision of pollination services by native bees in traditional slash-and-burn agriculture in the Yucatan Peninsula of tropical Mexico
January 08, 2017
Traditional tropical agriculture often entails a form of slash-and-burn land management that may adversely affect ecosystem services such as pollination, which are required for successful crop yields. Here we studied 37 local farmers’ chilli fields (sites) to evaluate the effects of land use composition on bee communities and, within 11 of these sites, we undertook experimental pollination treatments to quantify the pollination of chilli. We further explored the relationships between land use, bee community composition and pollination of chilli.
The structure of flower-visitor networks in relation to pollination across an agricultural to urban gradient
November 22, 2016
Insect mediated pollination is a key ecosystem service crucial for human nutrition, food production and wild plant reproduction. In our latest study we investigated the relative effects of local habitat quality and anthropogenic land use across an agricultural to urban gradient for local plant and flying insect communities. We quantified local flower-visitor networks and related network architecture to these local and landscape factors using structural equation modelling. Flower-visitor network architecture is often assumed to act as a surrogate for the ecosystem service of pollination. To test this idea, we related network metrics to pollination of four experimental, insect pollinator-dependent plant species.
Bumblebees pollinate urban gardens better than agricultural land
November11, 2016
Our latest paper investigating the potential combined effects of differing land use (specifically looking at urban areas and agricultural land) and parasites on the ecosystem service of pollination is featured in Issue 476 of the European Commision's Science for Environment Policy.
Linear mixed-effects models to control for the variability of microsatellite loci when comparing genetic diversity
July 15, 2016
There is general interest in comparing genetic variation among different populations, often measured as the number of alleles, allelic richness or heterozygosity, using multiple microsatellite genetic loci. The genetic variability among populations of a species is important because it can be considered an indirect measure of the evolvability of those populations. Yet microsatellite loci within the same species differ considerably in variability. The problem: which is the best way to test for variation in genetic diversity at microsatellite loci among populations using loci that are inherently different in their variability within a population?
Here we suggest the use of linear mixed-effects models (LMMs) to control for the variability of microsatellite loci (random part of the mixed model) when comparing genetic diversity.
Two tales of a city: Pollination services enhanced with urbanisation despite increasing pollinator parasitism
June 22, 2016
Pollination is a major ecosystem service, in which insects and particularly bees, play an important role for most angiosperm reproduction, including crop production. Among the major threats to insect pollinators, and consequently pollination services, are anthropogenic land use change and spread of pathogens. However, little is known so far about their interactive effects.
In our recent study, we performed a landscape-scale experiment using self-incompatible plant communities and empirically examined the relative effects of local habitat, anthropogenic land use and bumblebee parasitism on pollination of self-incompatible experimental plant communities.
Widespread risk of infectious diseases to wild bees
March 5, 2015
Bees are essential pollinators of wild flowers and crops used by humans for food, fiber and fuel. In our recent study we expand previous findings to show that several RNA viruses previously linked to honeybees are not only widespread in bumblebee populations, but that for at least one virus, disease prevalence in wild bumblebee populations is significantly higher than in managed honeybees. We go on to show that individual bumblebee foragers may contain high disease loads, and that several viruses are likely being transmitted between managed and wild bee pollinators.
