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Temperature, Pathogens and Chemicals: Stressors in a Changing World

Periodic Reporting for period 2 - TePaChe (Temperature, Pathogens and Chemicals: Stressors in a Changing World)

Reporting period: 2017-09-01 to 2018-08-31

Understanding relationships among multiple stressors – and the mechanisms underlying stressor interactions – will be crucial for applying ecological knowledge to solve future environmental problems. This Global Fellowship project aimed to address this problem by studying multiple stressors in a model system, filling knowledge gaps on the effects of simultaneous temperature, pollution and disease stress on animals. The proposed work combined theory and state-of-the-art methods from ecophysiology, ecotoxicology, immunology, evolutionary ecology and molecular biology, and had direct applications in environmental management and protection. The project used insects as model organisms, since they drive important ecological processes and are under high pressure from anthropogenic influences. To conclude, the project achieved most of its overall objectives; the project successfully explored factors and mechanisms affecting the plastic temperature tolerance, microbiota variation and neonicotinoid pesticide tolerance in the Drosophila models. Moreover, the project tested effects of various stressor combinations and stressor orders on survival and fitness parameters by using controlled experimental set up.
During the first year of her outgoing phase, Dr. Kaunisto, established the Drosophila experimental system, trained herself for the new methodology, conducted pilot experiments, participated in conferences, participated in outreach activities, collected some publishable data and wrote and published the refereed theoretical research article. During the second year of her outgoing phase, she conducted several experiments, participated in conferences and participated in outreach activities. During the third year (the return phase), Dr. Kaunisto organised and analysed the data and wrote the manuscripts for scientific publications. In her review article the fellow highlighted the need for more multi-stressor studies and suggested new approaches to move beyond descriptions of the effects of multiple stressors to a mechanistic and predictive understanding. Especially, it would be relevant to identify which stressor interactions, and species’ responses to them, are sufficiently generalizable (i.e. most or all related species respond similarly to the same stressor combination), and also predictable (for new combinations of stressors, or stressors acting via known mechanisms). The fellow and her collaborators found that Critical Thermal maximum in Drosophila is affected by increasing heating rates. Variation in microbiome community composition in different Drosophila species seems to be incongruent with Drosophila phylogeny. Combinations of different stressors impose different responses on an invasive pest species Drosophila suzukii. Thiachloprid exposure seems to change CYP genes expression. The project has been disseminated in various international conferences and local outreach activities in Canada and Finland. These results will be published in refereed scientific journals by the end of 2019 and they will form an important basis for future research in this field.
The project combined theory and state-of-the-art methods from ecophysiology, ecotoxicology, immunology, evolutionary ecology and molecular biology. In the study of thermal stress exposure, the fellow and her co-authors modified a specific device to measure both Ctmin and Ctmax (minimum and maximum critical thermal limits). Factors affecting the plastic Ctmax and mechanisms underlying the variation of the Ctmax of insects is a very topical issue in a changing climate. Measuring CTmax is relevant method because it is relatively fast, it yields parametric numbers that can be compared reasonably easily and it is intuitively related to obvious heatwave effects of climate change and distribution limits. The fellow and her collaborators used molecular methods such as DNA and RNA extraction, and amplicon sequencing (16S rRNA genes) using the unique barcodes and amplification procedure to study among-species differences in microbiota. In recent years, particular interest has focused on the importance of microbiome for immunity and other body functions as well as on the patterns of among-species variation in the microbiota. The fellow and her co-authors conducted the first comparable, phylogenetic study on the effects of a neonicotinoid pesticide, thiacloprid. Thiacloprid is a less-studied, but commonly used pesticide in Europe. At the moment thiacloprid is a “candidate for substitution” in EU due to its endocrine disrupting properties and possible detrimental effects on pollinators. The fellow also combined methods from thermal biology, microbiology and ecotoxicology by studying the single and multiple effects of the three important stressors (temperature stress, bacterial exposure and thiacloprid exposure). Prior to this project these interactions had not been well-explored for two stressors. Moreover, the effects of the three-stressor combination on insects had never been comprehensively investigated, even though these kinds of three-way interactions are very realistic in nature conditions. The research has many novel prospects and provides new understanding of effects of the chosen stressors both when applied in isolation and simultaneously. The project has applications in environmental management and protection. For example, interactions between environmental chemical stress and other stressors may lead to much greater / smaller sub-lethal effects (mechanistic cross-tolerance) than are presently explored when assessing safety of chemical compounds. Finally, this project yielded new information on the stress tolerance of the spotted wing Drosophila which is a highly invasive and economically important pest of various soft fruit and berries in Europe and North America.