TY - JOUR A1 - Voulgari‐Kokota, Anna A1 - Ankenbrand, Markus J. A1 - Grimmer, Gudrun A1 - Steffan‐Dewenter, Ingolf A1 - Keller, Alexander T1 - Linking pollen foraging of megachilid bees to their nest bacterial microbiota JF - Ecology and Evolution N2 - Solitary bees build their nests by modifying the interior of natural cavities, and they provision them with food by importing collected pollen. As a result, the microbiota of the solitary bee nests may be highly dependent on introduced materials. In order to investigate how the collected pollen is associated with the nest microbiota, we used metabarcoding of the ITS2 rDNA and the 16S rDNA to simultaneously characterize the pollen composition and the bacterial communities of 100 solitary bee nest chambers belonging to seven megachilid species. We found a weak correlation between bacterial and pollen alpha diversity and significant associations between the composition of pollen and that of the nest microbiota, contributing to the understanding of the link between foraging and bacteria acquisition for solitary bees. Since solitary bees cannot establish bacterial transmission routes through eusociality, this link could be essential for obtaining bacterial symbionts for this group of valuable pollinators. KW - foraging patterns KW - nest microbiota KW - plant–microbe–pollinator triangle KW - pollination network KW - solitary bees KW - wild bees Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201749 SN - 00 VL - 2019 IS - 9 ER - TY - JOUR A1 - Requier, Fabrice A1 - Jowanowitsch, Kim K. A1 - Kallnik, Katharina A1 - Steffan‐Dewenter, Ingolf T1 - Limitation of complementary resources affects colony growth, foraging behavior, and reproduction in bumble bees JF - Ecology N2 - Resource availability in agricultural landscapes has been disturbed for many organisms, including pollinator species. Abundance and diversity in flower availability benefit bee populations; however, little is known about which of protein or carbohydrate resources may limit their growth and reproductive performance. Here, we test the hypothesis of complementary resource limitation using a supplemental feeding approach. We applied this assumption with bumble bees (Bombus terrestris), assuming that colony growth and reproductive performance should depend on the continuous supply of carbohydrates and proteins, through the foraging for nectar and pollen, respectively. We placed wild‐caught bumble bee colonies along a landscape gradient of seminatural habitats, and monitored the colonies’ weight, foraging activity, and reproductive performance during the whole colony cycle. We performed supplemental feeding as an indicator of landscape resource limitation, using a factorial design consisting of the addition of sugar water (carbohydrate, supplemented or not) crossed by pollen (protein, supplemented or not). Bumble bee colony dynamics showed a clear seasonal pattern with a period of growth followed by a period of stagnation. Higher abundance of seminatural habitats resulted in reducing the proportion of pollen foragers relative to all foragers in both periods, and in improving the reproductive performance of bumble bees. Interestingly, the supplemental feeding of sugar water positively affected the colony weight during the stagnation period, and the supplemental feeding of pollen mitigated the landscape effect on pollen collection investment. Single and combined supplementation of sugar water and pollen increased the positive effect of seminatural habitats on reproductive performance. This study reveals a potential colimitation in pollen and nectar resources affecting foraging behavior and reproductive performance in bumble bees, and indicates that even in mixed agricultural landscapes with higher proportions of seminatural habitats, bumble bee populations face resource limitations. We conclude that the seasonal management of floral resources must be considered in conservation to support bumble bee populations and pollination services in farmlands. KW - bombus terrestris KW - seasonal phenology KW - reproductive performance KW - pollen and nectar resources KW - landscape structure KW - feeding experiment Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-211891 VL - 101 IS - 3 ER - TY - JOUR A1 - Boetzl, Fabian A. A1 - Schuele, Maren A1 - Krauss, Jochen A1 - Steffan‐Dewenter, Ingolf T1 - Pest control potential of adjacent agri‐environment schemes varies with crop type and is shaped by landscape context and within‐field position JF - Journal of Applied Ecology N2 - Increasing natural pest control in agricultural fields is an important aim of ecological intensification. Combined effects of landscape context and local placement of agri‐environmental schemes (AES) on natural pest control and within‐field distance functions of natural pest control agents have rarely been addressed but might affect the distribution of biocontrol providers. Importantly, it is currently unknown whether ecosystem services provided by adjacent AES are consistent for different crop types during crop rotation. In this study, we assessed whether crop rotation from oilseed rape to cereals altered within‐field distance functions of ground‐dwelling predators from adjacent agri‐environmental fields along a gradient in landscape context. Additionally, we recorded crop pests, predation rates, parasitoids as well as crop yields on a total of 30 study sites. Distance functions varied between trophic levels: Carabid richness decreased while densities of carabid beetles, staphylinid beetles as well as crop yields increased towards the field centres. Distance functions of parasitoids and pests were modulated by the amount of semi‐natural habitat in the surrounding landscape, while the effects of adjacent AES were limited. Distance decay functions found for ground‐dwelling predators in oilseed rape in the previous year were not always present in cereals. Increasing distance to the field edge also increased effects of crop rotation on carabid beetle assemblages, indicating a source habitat function of field edges. Synthesis and applications. Distance functions of natural pest control are not universal and the effects of agri‐environmental schemes (AES) in different adjacent crops during crop rotation vary and depend on ecological contrasts. A network of semi‐natural habitats and spatially optimized AES habitats can benefit pest control in agricultural landscapes, but constraints as a result of crop type need to be addressed by annually targeted, spatially shifting agri‐environment schemes for different crops. KW - cereals KW - distance gradient KW - ecological intensification KW - ecosystem services KW - ground‐dwelling predators KW - parasitoids KW - pest control KW - semi‐natural habitats Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218265 VL - 57 IS - 8 SP - 1482 EP - 1493 ER - TY - JOUR A1 - Mayr, Antonia V. A1 - Keller, Alexander A1 - Peters, Marcell K. A1 - Grimmer, Gudrun A1 - Krischke, Beate A1 - Geyer, Mareen A1 - Schmitt, Thomas A1 - Steffan‐Dewenter, Ingolf T1 - Cryptic species and hidden ecological interactions of halictine bees along an elevational gradient JF - Ecology and Evolution N2 - Changes of abiotic and biotic conditions along elevational gradients represent serious challenges to organisms which may promote the turnover of species, traits and biotic interaction partners. Here, we used molecular methods to study cuticular hydrocarbon (CHC) profiles, biotic interactions and phylogenetic relationships of halictid bees of the genus Lasioglossum along a 2,900 m elevational gradient at Mt. Kilimanjaro, Tanzania. We detected a strong species turnover of morphologically indistinguishable taxa with phylogenetically clustered cryptic species at high elevations, changes in CHC profiles, pollen resource diversity, and a turnover in the gut and body surface microbiome of bees. At high elevations, increased proportions of saturated compounds in CHC profiles indicate physiological adaptations to prevent desiccation. More specialized diets with higher proportions of low‐quality Asteraceae pollen imply constraints in the availability of food resources. Interactive effects of climatic conditions on gut and surface microbiomes, CHC profiles, and pollen diet suggest complex feedbacks among abiotic conditions, ecological interactions, physiological adaptations, and phylogenetic constraints as drivers of halictid bee communities at Mt. Kilimanjaro. KW - COI KW - cuticular chemistry KW - elevational gradient KW - Halictidae KW - microbiome metabarcoding KW - pollen metabarcoding Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238853 VL - 11 IS - 12 SP - 7700 EP - 7712 ER - TY - JOUR A1 - Redlich, Sarah A1 - Martin, Emily A. A1 - Steffan‐Dewenter, Ingolf T1 - Sustainable landscape, soil and crop management practices enhance biodiversity and yield in conventional cereal systems JF - Journal of Applied Ecology N2 - Input‐driven, modern agriculture is commonly associated with large‐scale threats to biodiversity, the disruption of ecosystem services and long‐term risks to food security and human health. A switch to more sustainable yet highly productive farming practices seems unavoidable. However, an integrative evaluation of targeted management schemes at field and landscape scales is currently lacking. Furthermore, the often‐disproportionate influence of soil conditions and agrochemicals on yields may mask the benefits of biodiversity‐driven ecosystem services. Here, we used a real‐world ecosystem approach to identify sustainable management practices for enhanced functional biodiversity and yield on 28 temperate wheat fields. Using path analysis, we assessed direct and indirect links between soil, crop and landscape management with natural enemies and pests, as well as follow‐on effects on yield quantity and quality. A paired‐field design with a crossed insecticide‐fertilizer experiment allowed us to control for the relative influence of soil characteristics and agrochemical inputs. We demonstrate that biodiversity‐enhancing management options such as reduced tillage, crop rotation diversity and small field size can enhance natural enemies without relying on agrochemical inputs. Similarly, we show that in this system controlling pests and weeds by agrochemical means is less relevant than expected for final crop productivity. Synthesis and applications. Our study highlights soil, crop and landscape management practices that can enhance beneficial biodiversity while reducing agrochemical usage and negative environmental impacts of conventional agriculture. The diversification of cropping systems and conservation tillage are practical measures most farmers can implement without productivity losses. Combining local measures with improved landscape management may also strengthen the sustainability and resilience of cropping systems in light of future global change. KW - crop management KW - ecological intensification KW - landscape heterogeneity KW - natural enemies KW - pests KW - soil characteristics KW - sustainable intensification KW - wheat yield Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228345 VL - 58 IS - 3 SP - 507 EP - 517 ER - TY - JOUR A1 - Lasway, Julius V. A1 - Peters, Marcell K. A1 - Njovu, Henry K. A1 - Eardley, Connal A1 - Pauly, Alain A1 - Steffan‐Dewenter, Ingolf T1 - Agricultural intensification with seasonal fallow land promotes high bee diversity in Afrotropical drylands JF - Journal of Applied Ecology N2 - The exponential increase in the human population in tandem with increased food demand has caused agriculture to be the global‐dominant form of land use. Afrotropical drylands are currently facing the loss of natural savannah habitats and agricultural intensification with largely unknown consequences for bees. Here we investigate the effects of agricultural intensification on bee assemblages in the Afrotropical drylands of northern Tanzania. We disentangled the direct effects of agricultural intensification and temperature on bee richness from indirect effects mediated by changes in floral resources. We collected data from 24 study sites representing three levels of management intensity (natural savannah, moderate intensive and highly intensive agriculture) spanning an extensive gradient of mean annual temperature (MAT) in northern Tanzania. We used ordinary linear models and path analysis to test the effects of agricultural intensity and MAT on bee species richness, bee species composition and body‐size variation of bee communities. We found that bee species richness increased with agricultural intensity and with increasing temperature. The effects of agricultural intensity and temperature on bee species richness were mediated by the positive effects of agriculture and temperature on the richness of floral resources used by bees. During the off‐growing season, agricultural land was characterized by an extensive period of fallow land holding a very high density of flowering plants with unique bee species composition. The increase in bee diversity in agricultural habitats paralleled an increasing variation of bee body sizes with agricultural intensification that, however, diminished in environments with higher temperatures. Synthesis and applications. Our study reveals that bee assemblages in Afrotropical drylands benefit from agricultural intensification in the way it is currently practiced. However, further land‐use intensification, including year‐round irrigated crop monocultures and excessive use of agrochemicals, is likely to exert a negative impact on bee diversity and pollination services, as reported in temperate regions. Moreover, several bee species were restricted to natural savannah habitats. To conserve bee communities and guarantee pollination services in the region, a mixture of savannah and agriculture, with long periods of fallow land should be maintained. KW - bee abundance KW - bee body size KW - bee species richness KW - forage resources KW - inter‐tegular distance KW - mean annual temperature KW - northern Tanzania KW - species community composition Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-311877 VL - 59 IS - 12 SP - 3014 EP - 3026 ER - TY - JOUR A1 - Sponsler, Douglas B. A1 - Requier, Fabrice A1 - Kallnik, Katharina A1 - Classen, Alice A1 - Maihoff, Fabienne A1 - Sieger, Johanna A1 - Steffan‐Dewenter, Ingolf T1 - Contrasting patterns of richness, abundance, and turnover in mountain bumble bees and their floral hosts JF - Ecology N2 - Environmental gradients generate and maintain biodiversity on Earth. Mountain slopes are among the most pronounced terrestrial environmental gradients, and the elevational structure of species and their interactions can provide unique insight into the processes that govern community assembly and function in mountain ecosystems. We recorded bumble bee–flower interactions over 3 years along a 1400‐m elevational gradient in the German Alps. Using nonlinear modeling techniques, we analyzed elevational patterns at the levels of abundance, species richness, species β‐diversity, and interaction β‐diversity. Though floral richness exhibited a midelevation peak, bumble bee richness increased with elevation before leveling off at the highest sites, demonstrating the exceptional adaptation of these bees to cold temperatures and short growing seasons. In terms of abundance, though, bumble bees exhibited divergent species‐level responses to elevation, with a clear separation between species preferring low versus high elevations. Overall interaction β‐diversity was mainly caused by strong turnover in the floral community, which exhibited a well‐defined threshold of β‐diversity rate at the tree line ecotone. Interaction β‐diversity increased sharply at the upper extreme of the elevation gradient (1800–2000 m), an interval over which we also saw steep decline in floral richness and abundance. Turnover of bumble bees along the elevation gradient was modest, with the highest rate of β‐diversity occurring over the interval from low‐ to mid‐elevation sites. The contrast between the relative robustness bumble bee communities and sensitivity of plant communities to the elevational gradient in our study suggests that the strongest effects of climate change on mountain bumble bees may be indirect effects mediated by the responses of their floral hosts, though bumble bee species that specialize in high‐elevation habitats may also experience significant direct effects of warming. KW - alpine plants KW - climate KW - elevation gradient KW - mountain ecology KW - pollination network Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287199 VL - 103 IS - 7 ER - TY - JOUR A1 - Gebert, Friederike A1 - Steffan‐Dewenter, Ingolf A1 - Kronbach, Patrick A1 - Peters, Marcell K. T1 - The role of diversity, body size and climate in dung removal: A correlative and experimental approach JF - Journal of Animal Ecology N2 - The mechanisms by which climatic changes influence ecosystem functions, that is, by a direct climatic control of ecosystem processes or by modifying richness and trait compositions of species communities, remain unresolved. This study is a contribution to this discourse by elucidating the linkages between climate, land use, biodiversity, body size and ecosystem functions. We disentangled direct climatic from biodiversity‐mediated effects by using dung removal by dung beetles as a model system and by combining correlative field data and exclosure experiments along an extensive elevational gradient on Mt. Kilimanjaro, Tanzania. Dung removal declined with increasing elevation, being associated with a strong reduction in the richness and body size traits of dung beetle communities. Climate influenced dung removal rates by modifying biodiversity rather than by direct effects. The biodiversity–ecosystem effect was driven by a change in the mean body size of dung beetles. Dung removal rates were strongly reduced when large dung beetles were experimentally excluded. This study underscores that climate influences ecosystem functions mainly by modifying biodiversity and underpins the important role of body size for dung removal. KW - altitudinal gradients KW - biodiversity–ecosystem functioning relationship KW - body size KW - diversity gradients KW - ecosystem services KW - land use KW - Scarabaeidae KW - temperature Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293907 VL - 91 IS - 11 SP - 2181 EP - 2191 ER - TY - JOUR A1 - Kohl, Patrick L. A1 - Steffan‐Dewenter, Ingolf T1 - Nectar robbing rather than pollinator availability constrains reproduction of a bee‐flowered plant at high elevations JF - Ecosphere N2 - Abiotic factors are generally assumed to determine whether species can exist at the extreme ends of environmental gradients, for example, at high elevations, whereas the role of biotic interactions is less clear. On temperate mountains, insect‐pollinated plant species with bilaterally symmetrical flowers exhibit a parallel elevational decline in species richness and abundance with bees. This suggests that the lack of mutualistic interaction partners sets the elevational range limits of plants via a reduction in reproductive success. We used the bee‐pollinated mountain plant Clinopodium alpinum (Lamiaceae), which blooms along a continuous 1000‐m elevational gradient and has bilaterally symmetrical flowers, as a model to test the predicted parallel elevational decline in flower visitation and seed production. Although the community of flower visitors changed with elevation, the flower visitation rate by the most frequent visitors, bumble bees (33.8% of legitimate visits), and the overall rate of flower visitation by potential pollinators did not vary significantly with elevation. However, we discovered that nectar robbing by bumble bees and nectar theft by ants, two interactions with potentially negative effects on flowers, sharply increased with elevation. Seed set depended on pollinators across elevations and followed a weak hump‐shaped pattern, peaking at mid‐elevations and decreasing by about 20% toward both elevational range edges. Considering the mid‐ and high elevations, elevational variation in seed production could not be explained by legitimate bee visitation rates but was inversely correlated with the frequency of nectar robbing. Our observations challenge the hypothesis that a decrease in the availability of pollinators limits seed production of bee‐flowered plants at high elevations but suggest that an increase in negative interactions (nectar robbing and larceny) constrains reproductive success. KW - altitudinal gradients KW - bee pollination KW - chalcidoid wasps KW - climatic gradients KW - elevational diversity patterns KW - floral larceny KW - fly pollination KW - mountain ecosystems KW - plant–pollinator interactions KW - range limits KW - zygomorphy Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287141 VL - 13 IS - 6 ER - TY - JOUR A1 - Hornick, Thomas A1 - Richter, Anett A1 - Harpole, William Stanley A1 - Bastl, Maximilian A1 - Bohlmann, Stephanie A1 - Bonn, Aletta A1 - Bumberger, Jan A1 - Dietrich, Peter A1 - Gemeinholzer, Birgit A1 - Grote, Rüdiger A1 - Heinold, Bernd A1 - Keller, Alexander A1 - Luttkus, Marie L. A1 - Mäder, Patrick A1 - Motivans Švara, Elena A1 - Passonneau, Sarah A1 - Punyasena, Surangi W. A1 - Rakosy, Demetra A1 - Richter, Ronny A1 - Sickel, Wiebke A1 - Steffan‐Dewenter, Ingolf A1 - Theodorou, Panagiotis A1 - Treudler, Regina A1 - Werchan, Barbora A1 - Werchan, Matthias A1 - Wolke, Ralf A1 - Dunker, Susanne T1 - An integrative environmental pollen diversity assessment and its importance for the Sustainable Development Goals JF - Plants, People, Planet N2 - Societal Impact Statement Pollen relates to many aspects of human and environmental health, which protection and improvement are endorsed by the United Nations Sustainable Development Goals. By highlighting these connections in the frame of current challenges in monitoring and research, we discuss the need of more integrative and multidisciplinary pollen research related to societal needs, improving health of humans and our ecosystems for a sustainable future. Summary Pollen is at once intimately part of the reproductive cycle of seed plants and simultaneously highly relevant for the environment (pollinators, vector for nutrients, or organisms), people (food safety and health), and climate (cloud condensation nuclei and climate reconstruction). We provide an interdisciplinary perspective on the many and connected roles of pollen to foster a better integration of the currently disparate fields of pollen research, which would benefit from the sharing of general knowledge, technical advancements, or data processing solutions. We propose a more interdisciplinary and holistic research approach that encompasses total environmental pollen diversity (ePD) (wind and animal and occasionally water distributed pollen) at multiple levels of diversity (genotypic, phenotypic, physiological, chemical, and functional) across space and time. This interdisciplinary approach holds the potential to contribute to pressing human issues, including addressing United Nations Sustainable Development Goals, fostering social and political awareness of these tiny yet important and fascinating particles. KW - aerobiology KW - allergy KW - diversity KW - environmental monitoring KW - food safety KW - paleoecology KW - palynology KW - pollination Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-276487 VL - 4 IS - 2 SP - 110 EP - 121 ER -