Applied statistics in field and semi-field studies with bees

Field and semi-field studies are important tools in the ecotoxicological risk assessment of plant protection products for bees (honey bees, bumblebees and solitary bees). While these studies represent far more realistic conditions than laboratory tests, they also present a challenge for the analysis and interpretation due to the large and complex datasets. Therefore, in order to correctly answer the underlying ecotoxicological questions, it is crucial that these studies are not only thoroughly planned and conducted, it is also important that they are subjected to adequate statistical analysis. Our aim is to provide a better understanding on how to conduct and interpret statistical analyses in field and semi-field studies with bees made for regulatory purposes. An overview of how study design and statistics should be aligned with each other is given including the specific challenges of (semi-) field trials, as for instance how to address the problem of pseudoreplication if hives are regarded as experimental units. Different statistical tools are compared and their suitability for different data types and questions are discussed. Generalized Linear (Mixed) Models (GLMMs) are evaluated in more detail as they provide a flexible and robust tool for the analysis of honey bee (semi-) field data. Furthermore, some more light is shed on what p-values really tell us, how they can help to interpret data and how they should not be misinterpreted.Field and semi-field studies are important tools in the ecotoxicological risk assessment of plant protection products for bees (honey bees, bumblebees and solitary bees). While these studies represent far more realistic conditions than laboratory tests, they also present a challenge for the analysis and interpretation due to the large and complex datasets. Therefore, in order to correctly answer the underlying ecotoxicological questions, it is crucial that these studies are not only thoroughly planned and conducted, it is also important that they are subjected to adequate statistical analysis. Our aim is to provide a better understanding on how to conduct and interpret statistical analyses in field and semi-field studies with bees made for regulatory purposes. An overview of how study design and statistics should be aligned with each other is given including the specific challenges of (semi-) field trials, as for instance how to address the problem of pseudoreplication if hives are regarded as experimental units. Different statistical tools are compared and their suitability for different data types and questions are discussed. Generalized Linear (Mixed) Models (GLMMs) are evaluated in more detail as they provide a flexible and robust tool for the analysis of honey bee (semi-) field data. Furthermore, some more light is shed on what p-values really tell us, how they can help to interpret data and how they should not be misinterpreted

ICPPR WG Semi-field and field Report and Discussion

The ICPPR Semi-Field/Field Testing (SF/FT) workgroup consists of several ‘writing groups’ that are focused developing technical guidance that is focused on 4 separate but related topics: 1) designing and conducting pollen and nectar residue studies, 2) conducting large scale colony feeding studies, 3) updating guidance for conducting semi-field tunnel studies, and 4) design and interpretation of full field studies with bees. What follows is the current status of each of these activities.The ICPPR Semi-Field/Field Testing (SF/FT) workgroup consists of several ‘writing groups’ that are focused developing technical guidance that is focused on 4 separate but related topics: 1) designing and conducting pollen and nectar residue studies, 2) conducting large scale colony feeding studies, 3) updating guidance for conducting semi-field tunnel studies, and 4) design and interpretation of full field studies with bees. What follows is the current status of each of these activities

Impacts of the invasive alien Heracleum mantegazzianum on native plant-pollinator interactions

Zumkier U. Impacts of the invasive alien Heracleum mantegazzianum on native plant-pollinator interactions. Bielefeld: Universität; 2012.Pollination is one of the most essential ecosystems services, it is crucial to the reproduction of most flowering plants, and plays an important role in crop production. This fundamental ecosystem service is threatened by the ongoing global change, which includes climatic change, changes in land use, and the introduction and spread of alien species. Alien plants may have a negative impact on native plants when they compete for pollination services. Effects of competi- tion for pollinators may have an impact on the quantity as well as the quality of pollination. The quantity of pollination adresses the number of visits a plant receives, while the quality of pollina- tion describes the number of transferred pollen grains. The complex interactions of these factors determines the outcome of seed set for a plant. Ultimately, a negtive affection of these compo- nents may lead to a reduction of plant fitness. The fact that alien plants often have large showy inflorescences as they were commonly introduced as ornamentals makes them potentially supe- rior competitors. Alien plants have been shown to affect the quantity as well as the quality of co- flowering native species. Furthermore, it has to be taken into consideration that species do not interact in a vacuum, plants and pollinators form a mutualistic interaction network. While there is evidence that alien plants are well-integrated into interaction networks, there is still a demand to know if this integration translates into effects on the quality of pollination and reproductive success of a community of co-flowering plants. Aim of this thesis was to scrutinize the impacts of the alien invasive plant Heracleum mantegaz- zianum on native plant-pollinator systems. Due to its tall growth and large compound inflores- cences H. mantegazzianum definitively has the potential to affect the pollination of native plants. In order to find out about the pollinators of the invader a field study was conducted, which included observation of flowers and measurements of pollinator efficiency. The same measure- ments were made for the native closely related Heracleum sphondylium in order to detect an overlap of pollinator faunas. An experimental garden setup was used in order to determine the effect of the invader on insect visitation and set seed of an array of co-flowering plants. Addi- tionally, I used a network approach to explore the impact of H. mantegazzianum on two- and one-mode network parameters. Furthermore, the transport of alien pollen was quantified and network parameters of networks based on visitation, interaction and pollen transfer were com- pared. Results show that the large inflorescences of the invader were highly attractive to a broad range of insects, yet there were just a few insects truly important pollinators, most of all the honeybee Apis mellifera. There was low potential for competition between the two Heracleum-species, yet the invader might have a potential to influence native plant-pollinator interactions due to its association with the super-generalist A. mellifera. However, results of the experimental garden revealed that visitation rates of co-flowering plants were (although statistically non-significant) generally enhanced, and the effect on seed set was neutral. H. mantegazzianum was found not only to be well integrated, but dominant in invaded visitation networks. Nevertheless, in com- bination with the results for seed set it was concluded that the impact of the invader was not detrimental to the invaded plant-pollinator system. Additionally, I could show that, while flower visitors of H. mantegazzianum were less constant than on other plants and there were plant-to- plant interactions for all co-flowering plants, still little alien pollen was transferred. Neverthe- less, there was a potentially competitive effect of conspecific pollen loss depending on the plant species. Network analysis showed that the alien plant was only dominant in terms of visitation but not in terms of interspecific pollen potentially transferred. This highlights that both, the quantity and the quality component, need to be assessed to create an adequate estimate on the impact of an invader on plant-pollinator systems

Auswirkungen der invasiven Art Heracleum mantegazzianum (Riesenbärenklau) auf einheimische Pflanze-Bestäuber-Systeme

Zumkier U, Kraemer M. Auswirkungen der invasiven Art Heracleum mantegazzianum (Riesenbärenklau) auf einheimische Pflanze-Bestäuber-Systeme. In: Feit U, Korn H, eds. Treffpunkt Biologische Vielfalt IX: Aktuelle Forschung im Rahmen des Übereinkommens über die biologische Vielfalt. BfN-Skripten. Vol 265. Bonn: Bundesamt für Naturschutz; 2010: 109-113

High competitiveness of a resource demanding invasive acacia under low resource supply

Werner C, Zumkier U, Beyschlag W, Maguas C. High competitiveness of a resource demanding invasive acacia under low resource supply. PLANT ECOLOGY. 2010;206(1):83-96.Mechanisms controlling the successful invasion of resource demanding species into low-resource environments are still poorly understood. Well-adapted native species are often considered superior competitors under stressful conditions. Here we investigate the competitive ability of the resource demanding alien Acacia longifolia, which invades nutrient-poor Mediterranean sand dunes such as in coastal areas of Portugal. We explore the hypothesis that drought may limit invasion in a factorial competition experiment of the alien invasive versus two native species of different functional groups (Halimium halimifolium, Pinus pinea), under well-watered and drought conditions. Changes in biomass, allocation pattern, and N-uptake-efficiency (via N-15-labeling) indicated a marked drought sensitivity of the invader. However, highly efficient drought adaptations of the native species did not provide a competitive advantage under water limiting conditions. The competitive strength of H. halimifolium towards the alien invader under well-watered conditions turned into a positive interaction between both species under drought. Further, low resource utilization by native species benefited A. longifolia by permitting continued high nitrogen uptake under drought. Hence, the N-fixing invader expresses low plasticity by continuous high resource utilization, even under low resource conditions. The introduction of novel traits into a community like N-fixation and high resource use may promote A. longifolia invasiveness through changes in the physical environment, i.e., the water and nutrient cycle of the invaded sand dune system, thereby potentially disrupting the co-evolved interactions within the native plant community