Sara Diana Leonhardt

Technische Universität München | TUM · Department of Ecology and Ecosystem Management

Hybrid intelligence - arising from the sensible, targeted fusion of human minds and cutting-edge computational systems-holds great potential for enhancing the sustainability of agriculture. Leveraging the combined strengths of both collective human and artificial intelligence helps identify and stress-test pathways towards the reconciliation of bio...

Bees are the most important group of insect pollinators, but their populations are declining. To gain a better understanding of wild bee responses to different stressors (e.g. land-use change) and conservation measures, regional and national monitoring schemes are currently being established in Germany, which is used here as a model region, and in...

Stingless bees are important pollinators in tropical forests. Yet, we know little about their foraging behavior (e.g., their nutritional requirements or their floral sources visited for resource collection). Many stingless bees not only depend vitally on pollen and nectar for food but also on resin for nest building and/or defense. However, it is u...

Pollination is an important ecosystem service for both crop and wild plants. In recent decades, many pollinators have been experiencing population declines due to land-use changes and intensified agriculture. However, effects of anthropogenic landscapes on bee pollinators in the tropics are still little investigated. We analyzed the effects of land...

In agricultural landscapes, bees face a variety of stressors, including insecticides and poor-quality food. Although both stressors individually have been shown to affect bumblebee health negatively, few studies have focused on stressor interactions, a scenario expected in intensively used agricultural landscapes. Using the bumblebee Bombus terrest...

Tick-borne diseases raise serious health concerns for both humans and animals. Tick control and disease prevention largely depend on synthetic acaricides and repellents, often incriminated for high toxicity. To find alternative, safe, and efficient agents against ticks, research on plant-based volatile terpenes constitutes a promising direction. Th...

Background Pollinating insects provide economically and ecologically valuable services, but are threatened by a variety of anthropogenic changes. The availability and quality of floral resources may be affected by anthropogenic land use. For example, flower-visiting insects in agroecosystems rely on weeds on field edges for foraging resources, but...

Insects are equipped with neurological, physiological, and behavioral tools to locate potential food sources and assess their nutritional quality based on volatile and chemotactile cues. We summarize current knowledge on insect taste perception and the different modalities of reception and perception. We suggest that the neurophysiological mechanis...

Introduction Pollen is an important tissue in plants that plays a vital role in plant reproduction as it carries male gametes and occasionally also serves as a pollinator reward. There has been an increasing interest in pollen chemistry due to the impact of chemical variation on pollinator choices and well-being, especially in bees. The pollen fat...

Premise: Many flowering plants depend on insects for pollination and thus attract pollinators by offering rewards, mostly nectar and pollen. Bee pollinators rely on pollen as their main nutrient source. Pollen provides all essential micro- and macronutrients including substances that cannot be synthesized by bees themselves, such as sterols, which...

An intriguing yet little studied aspect of social insect foraging is the use of resources other than food. We are interested in the collection of plant resins for nest construction and defense by tropical stingless bees. However, direct observations of stingless bee foraging and potential predation activities by natural enemies at resin sources are...

Traits have become a crucial part of ecological and evolutionary sciences, helping researchers understand the function of an organism's morphology, physiology, growth and life history, with effects on fitness, behaviour, interactions with the environment and ecosystem processes. However, measuring, compiling and analysing trait data comes with data...

During the main COVID-19 global pandemic lockdown period of 2020 an impromptu set of pollination ecologists came together via social media and personal contacts to carry out standardised surveys of the flower visits and plants in gardens. The surveys involved 67 rural, suburban and urban gardens, of various sizes, ranging from 61.18° North in Norwa...

Context Pollination is an important ecosystem service for both crop and wild plants. In recent decades, many pollinators have been experiencing population declines due to land-use changes and intensified agriculture. However, effects of anthropogenic landscapes on bee pollinators in the tropics are still little investigated. Objectives We analyzed...

Context Pollination is an important ecosystem service for both crop and wild plants. In recent decades, many pollinators have been experiencing population declines due to land-use changes and intensified agriculture. However, effects of anthropogenic landscapes on bee pollinators in the tropics are still little investigated. Objectives We analyzed...

Flower-visiting insects in agroecosystems forage on field-edge weeds often exposed to agrochemicals that may compromise the quality of their floral resources. We conducted complementary field and greenhouse experiments to evaluate the: 1) effect of low concentrations of agrochemical exposure on nectar and pollen quality and 2) relationship between...

Biodiversity loss, as often found in intensively managed agricultural landscapes, correlates with reduced ecosystem functioning, for example, pollination by insects, and with altered plant composition, diversity, and abundance. But how does this change in floral resource diversity and composition relate to occurrence and resource use patterns of tr...

Bee performance and well-being strongly depend on access to sufficient and appropriate resources, in particular pollen and nectar of flowers, which constitute the major basis of bee nutrition. Pollen-derived microbes appear to play an important but still little explored role in the plant pollen–bee interaction dynamics, e.g. through affecting quant...

Wild bee populations are declining due to human activities, such as land use, which strongly affect the composition and diversity of available plants and food sources. The chemical composition of food (i.e. nutrition), in turn, determines health, resilience and fitness of bees. However, for pollinators, the term health is recent and subject to deba...

Bee homing capacity determines the maximum distance/area from/around the nest that workers can travel to exploit resources. However, homing ranges have been hardly examined in tropical Asian stingless bee species or in relation to anthropogenic land‐use changes. Here, we used translocation experiments, where we released marked bees at different dis...

1. Overall, more than 30% of bee species depend on non-floral resources, such as resin. However, the importance of resin in bee ecology, particularly for solitary bees, has received very little attention thus far. 2. A plethora of loose natural history observations, inferences, and author opinions hint towards a striking range of uses of resin for...

• Floral nectar is considered the most important floral reward for attracting pollinators. It contains large amounts of carbohydrates besides variable concentrations of amino acids and thus represents an important food source for many pollinators. Its nutrient content and composition can, however, strongly vary within and between plant species. The...

The nutritional composition of food is often complex as resources contain a plethora of different chemical compounds, some of them more, some less meaningful to consumers. Plant pollen, a major food source for bees, is of particular importance as it comprises nearly all macro- and micronutrients required by bees for successful development and repro...

Bees provide essential ecosystem services such as crop pollination, but perennial colonies of social species require year-round access to floral resources, especially in resource-poor agricultural landscapes. We investigated pollen resources used by a social bee (Tetragonula carbonaria, Meliponini) in forests and orchards of subtropical Australia....

The majority of flowering plants relies on animal pollinators for sexual reproduction and many animal pollinators rely on floral resources. However, interests of plants and pollinators are often not the same, resulting in an asymmetric relationship that ranges from mutualistic to parasitic interactions. Our understanding of the processes that under...

The decline of both managed and wild bee populations has been extensively reported for over a decade now, with growing concerns amongst the scientific community. Also, evidence is growing that both managed and feral honey bees may exacerbate threats to wild bees. In Australia, there are over 1600 native bee species and introduced European honey bee...

(1) Background: Landscape simplification is a major threat to bee and wasp conservation in the tropics, but reliable, long-term population data are lacking. We investigated how community composition, diversity, and abundance of tropical solitary bees and wasps change with landscape simplification (plant diversity, plant richness, distance from fore...

Bees rely on floral pollen and nectar for food. Therefore, pollinator friendly plantings are often used to enrich habitats in bee conservation efforts. As part of these plantings, non‐native plants may provide valuable floral resources, but their effects on native bee communities have not been assessed in direct comparison with native pollinator fr...

Growing evidence reveals strong overlap between microbiomes of flowers and bees, suggesting that flowers are hubs of microbial transmission. Whether floral transmission is the main driver of bee microbiome assembly, and whether functional importance of florally sourced microbes shapes bee foraging decisions are intriguing questions that remain unan...

An adequate supply of macro- and micronutrients determines health and reproductive success in most animals. Many bee species, for example, collect nectar and pollen to satisfy their demands for carbohydrates, protein and fat, respectively. Bees can assess the quality of pollen by feeding on it, but also pre-digestively by means of chemotactile asse...

Insects have evolved an extraordinary range of nutritional adaptations to exploit other animals, plants, bacteria, fungi and soils as resources in terrestrial and aquatic environments. This special issue provides some new insights into the mechanisms underlying these adaptations. Contributions comprise lab and field studies investigating the chemic...

Dietary macro-nutrients (i.e., carbohydrates, protein, and fat) are important for bee larval development and, thus, colony health and fitness. To which extent different diets (varying in macro-nutrient composition) affect adult bees and whether they can thrive on nectar as the sole amino acid source has, however, been little investigated. We invest...

EKLIPSE received a request by Pollinis on the 30th of June 2018, to produce an overview of the current knowledge and research gaps related to the impacts of pesticide and fertilizer use in farmland on the effectiveness of adjacent pollinator conservation measures. The call was answered through a Joint Fact Finding approach, including a workshop on...

Bees need food of appropriate nutritional quality to maintain their metabolic functions. They largely obtain all required nutrients from floral resources, i.e., pollen and nectar. However, the diversity, composition and nutritional quality of floral resources varies with the surrounding environment and can be strongly altered in human-impacted habi...

Land-use change and habitat loss have profoundly disturbed the resource availability for many organisms in farmlands, including bees. To counteract the resulting decline of bees and to maintain their pollination service to crops, bee pollinator-friendly schemes have been developed. We assessed the most established bee pollinator-friendly schemes wh...

Nectar is crucial to maintain plant-pollinator mutualism. Nectar quality (nutritional composition) can vary strongly between individuals of the same plant species. The factors driving such inter-individual variation have however not been investigated closer. We investigated nectar quality of field scabious, Knautia arvensis in different grassland p...

Preventing malnutrition through consuming nutritionally appropriate resources represents a challenge for foraging animals. This is due to often high variation in the nutritional quality of available resources. Foragers consequently need to evaluate different food sources. However, even the same food source can provide a plethora of nutritional and...

Several studies have highlighted the importance of natural habitat to support bees in disturbed landscapes such as agroecosystems. However, little is known about the specific habitat requirements of solitary bees in such landscapes. We aimed to identify the plant sources of nest materials and brood provisions for cavity-nesting solitary bees in nat...

A prime example of plant–animal interactions is the interaction between plants and pollinators, which typically receive nectar and/or pollen as reward for their pollination service. While nectar provides mostly carbohydrates, pollen represents the main source of protein and lipids for many pollinators. However, the main function of pollen is to car...

Like all animals, bees need to consume essential amino acids to maintain their body’s protein synthesis. Perception and discrimination of amino acids are, however, still poorly understood in bees (and insects in general). We used chemotactile conditioning of the proboscis extension response (PER) to examine (1) whether Bombus terrestris workers are...

Stingless bees are highly social pollinators in tropical ecosystems. Besides floral pollen and nectar, they collect substantial amounts of plant resins, which are used for nest construction/maintenance and defence against antagonists. Moreover, some stingless bees extract chemical compounds from resins and incorporate them in their cuticular chemic...

Sand mines represent anthropogenically impacted habitats found worldwide, which bear potential for bee conservation. Although floral resources can be limited at these habitats, vegetation free patches of open sandy soils and embankments may offer good nesting possibilities for sand restricted and other bees. We compared bee communities as found in...

Honeybees (Apis mellifera) are threatened by numerous pathogens and parasites. To prevent infections they apply cooperative behavioral defenses, such as allo-grooming and hygiene, or they use antimicrobial plant resin. Resin is a chemically complex and highly variable mixture of many bioactive compounds. Bees collect the sticky material from differ...

Exemplary chromatograms. (DOCX)

List of all substances identified from resin samples of trees, bees and propolis and their relative amounts. (XLSX)

List of substance classes and number components identified from resin samples. (DOCX)

Location of the study apiaries. (DOCX)

Bees receive nectar and pollen as reward for pollinating plants. Pollen of different plant species varies widely in nutritional composition. In order to select pollen of appropriate nutritional quality, bees would benefit if they could distinguish different pollen types. Whether they rely on visual, olfactory and/or chemotactile cues to distinguish...

Percentage of proboscis extension responses (%PER) shown by Apis mellifera individuals (N = 39) in differential olfactory conditioning to the odor of apple versus almond pollen over 10 trials with separate lines for rewarded (S+, filled symbols) and unrewarded (S-, clear symbols) stimuli. Both, apple (grey) and almond (black) pollen were used as S+...

Number of individuals showing a proboscis extension response (PER) (dark grey) and not showing a PER (light grey) in the first trial of all experiments performed. There were no significant differences (n.s.) between different seasons or light conditions (Chi22 = 0.82, P = 0.663). (TIF)

Number of proboscis extension responses (PER) shown by Apis mellifera individuals (N = 132) in differential chemotactile conditioning of summer (N = 64, left) and winter (N = 64, right) bees to the taste of apple versus almond pollen. Boxplots display responses to S+ and S-. S+ represents the rewarded stimulus, S- the unrewarded stimulus. Both, app...

Amino acid content (in μmol/g dry weight) of apple and almond pollen used in the PER experiments: determined via ion exchange chromatography (see [27]). In addition to concentrations of 20 protein-coding amino acids, concentrations for gamma-Aminobutyric acid (GABA) and hydroxyproline are provided. (DOCX)

Percentage of proboscis extension responses (%PER) shown by Apis mellifera individuals (N = 64) in differential chemotactile conditioning in the dark to the taste of apple versus almond pollen over 10 trials with all stimuli separated. S+ (filled) represents the rewarded conditioned stimulus, S- (clear) the unrewarded conditioned stimulus. Both, ap...

Dataset for the paper "Friends or relatives: which factors determine floral pollen nutritional quality?"

Bee population declines are often linked to human impacts, especially habitat and biodiversity loss, but empirical evidence is lacking. To clarify the link between biodiversity loss and bee decline, we examined how floral diversity affects (reproductive) fitness and population growth of a social stingless bee. For the first time, we related availab...

Alpine Bombus International Meeting 29th-31st July, 2018 Book of Abstracts

Data on chemotactile and olfactory PER conditioning to test which stimuli honeybees use to differentiate between different pollen types

Trap nests or “bee hotels” have been used to manage solitary bees since the 1950s in agriculture, research and, more recently, for urban conservation. Various designs are available for different purposes and target species, however, site characteristics such as land use also need to be considered. In this study, we test the performance of a hybrid...

Plant performance is correlated with element concentrations in plant tissue, which may be impacted by adverse chemical soil conditions. Antibiotics of veterinary origin can adversely affect plant performance. They are released to agricultural fields via grazing animals or manure, taken up by plants and may be stored, transformed or sequestered by p...

data set used to test for effect of habitat and surrounding plant species richness on various fitness parameters in the Australian stingless bee Tetragonula carbonaria

Stingless bees (Hymenoptera, Apidae: Meliponini) represent a highly diverse group of social bees confined to the world's tropics and subtropics. They show a striking diversity of structural and behavioral adaptations and are important pollinators of tropical plants. Despite their diversity and functional importance, their ecology, and especially ch...

Numerous studies revealed a positive relationship between biodiversity and ecosystem functioning, suggesting that biodiverse environments may not only enhance ecosystem processes, but also benefit individual ecosystem members by, for example, providing a higher diversity of resources. Whether and how the number of available resources affects resour...

Antibiotics of veterinary origin are released to agricultural fields via grazing animals or manure. Possible effects on human health through the consumption of antibiotic exposed crop plants have been intensively investigated. However, information is still lacking on the effects of antibiotics on plants themselves, particularly on non-crop species,...

Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking. We assessed the phenotypic integration of CCDs in a meta‐analysis to characterize patterns of covariation in CCDs and ide...

When tasting food, animals rely on chemical and tactile cues, which determine the animal’s decision on whether or not to eat food. As food nutritional composition has enormous consequences for the survival of animals, food items should generally be tasted before they are eaten or collected for later consumption. Even though recent studies confirmed...

Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in...

Tree invasions have substantial impacts on biodiversity and ecosystem functioning, and trees that are dispersed by animals are more likely to become invasive. In addition, hybridisation between plants is well documented as a source of new weeds, as hybrids gain new characteristics that allow them to become invasive. Corymbia torelliana is an invasi...

Context Abundance and diversity of bumblebees have been declining over the past decades. To successfully conserve bumblebee populations, we need to understand how landscape characteristics affect the quantity and quality of floral resources collected by colonies and subsequently colony performance. Objectives We therefore investigated how amount an...

To date, no study has investigated how landscape structural (visual) alterations affect navigation and thus homing success in stingless bees. We addressed this question in the Australian stingless bee Tetragonula carbonaria by performing marking, release and re-capture experiments in landscapes differing in habitat homogeneity (i.e., the proportion...

Nutritional deficits may be one factor contributing to the ongoing decline of wild and managed bees. As a consequence, interest in understanding the effect of floral resource availability on nutritional intake - and subsequently bee health and performance - has increased. However, the proximate mechanisms underlying bee foraging choices are still p...

Access to abundant and diverse floral plant sources is essential for generalist bees as they obtain all energy and nutrients required from pollen and nectar. Despite their importance, we still know little about the precise nutritional requirements of most bee species. Here, we investigated differences in floral and amino acid profiles of pollen col...

Insect life strategies comprise all levels of sociality from solitary to eusocial, in which individuals form persistent groups and divide labor. With increasing social complexity, the need to communicate a greater diversity of messages arose to coordinate division of labor, group cohesion, and concerted actions. Here we summarize the knowledge on p...

Increasing human land use for agriculture and housing leads to the loss of natural habitat and to widespread declines in wild bees. Bee foraging dynamics and fitness depend on the availability of resources in the surrounding landscape, but how precisely landscape related resource differences affect bee foraging patterns remains unclear. To investig...

Table S1. Location of study sites and geographic information. Data S1. Influence of daytime. Table S2. Spearman correlation matrix with correlation coefficients (rS) for forager numbers and weather variables. Table S3. Results of generalized linear mixed effect models (GLMMs) for each response variable, for the second year with all weather facto...

Tree invasions have substantial impacts on biodiversity and ecosystem functioning, and trees that are dispersed by animals are more likely to become invasive. In addition, hybridisation between plants is well documented as a source of new weeds, as hybrids gain new characteristics that allow them to become invasive. Corymbia torelliana is an invasi...

Body surfaces of organisms must prevent desiccation and inhibit the intrusion of harmful compounds and organisms. In insects, these functions are fulfilled by their cuticle, of which the external one represents a lipid layer that comprises different compound groups with various functions. In the highly social stingless bees, cuticular compounds are...

Increasing human land use for farming and housing led to the loss of natural habitat and to widespread declines in wild bees, which in turn puts pollination services at risk. The quantity and quality of plant resources available in a landscape drive bee foraging dynamics and hence fitness of bee colonies. Yet how bee foraging patterns and colony pe...

In view of the ongoing pollinator decline, the role of nutrition in bee health has received increasing attention. Bees obtain fat, carbohydrates and protein from pollen and nectar. As both excessive and deficient amounts of these macronutrients are detrimental, bees would benefit from assessing food quality to guarantee an optimal nutrient supply....

Bumble bees play an important role as pollinators of many crop plants and wild flowers. As in many wild bees, their abundance and diversity have declined in recent years, which may threaten the stability of pollination services. The observed decline is often linked with the loss or alteration of natural habitat, e.g., through urbanization, the conv...

Many insect groups are important mutualistic partners of plants. Bees in particular provide an essential mutualistic service to plants: pollination of their flowers. They can also act as seed dispersers for plants, a rare seed dispersal mutualism termed melittochory. One group of known bee seed dispersers are stingless bees (Apidae: Meliponini). Au...