Modelling Climatic Suitability and Dispersal of European Sandfly

Climate change has been linked to an increase in the spreading of vector-borne diseases. Fischer et al. (2011) used ecological niche modelling to predict sandfly dispersal in Central Europe, in the face of climate change. The model combined climate suitability and specific dispersal pathways for the Phlebotomus perniciosus species. A cost surface analysis was used to show potential dispersal areas based upon geographically suitable habitats. It was found that climate change significantly increased vector dispersal. River valleys would be dispersal pathways, while mountains would inhibit species dispersal.—Simone Berkovitz
Fischer, D., Thomas, S., Beierkuhnlein, C. 2011. Modelling climatic suitability and dispersal for disease vectors: the example of a phlebotomine sandfly in Europe. Procedia Enviro Sciences. 7, 164–169.

            Previous research has indicated that because most disease vectors are ectothermal arthropods, which cannot regulate their body temperatures, climate change influences disease prevalence. The majority of research focuses on mosquito-borne diseases such as Malaria and Dengue-fever, while sandfly-borne diseases are less studied. However, Leishmaniasis the disease associated with sandflies, constitutes a serious animal and health concern in most areas of the world. Recently, phlebotomine sandflies, which were thought to be restricted to the Mediterranen, have been found in typically colder Northern areas of central Europe, which may indicate expansion due to increasing temperatures. Therefore Fischer et al. found it necessary to investigate the relationship between climate suitability and species dispersal ability. The authors proposed an ecological niche model that combined specific dispersal pathways of the P. perniciosus species with changing climatic niches.
            Using bioclimatic variables, maximum entropy algorithms were used in order to model the distribution due to climate suitability of P. perniciosus  in Bavaria (Southeast Germany). In order to predict the future climate suitability, a regional climate model of Europe was applied. Then, a least-cost analysis was used to identify potential dispersal pathways. Least costs refer to the least amount of effort for a species moving through a geographic area, which helps to predict species’ pathways. The analysis consisted of identifying the cost surface, the climatic suitability of the current and future time periods, and cost distance, which quantifies the dispersal pathways based upon accessibility.
            From the first model, Fischer et al. found that currently only a very small region in the outermost Northwest of Bavaria is climatically suitable for P.perniciosus. However, when the future climate model was applied, significantly more regions were found to be suitable.  The cost analysis showed river valleys to be the preferred dispersal pathways, while high mountainous regions were found to be barriers that exclude dispersal. From the model, the authors were able to predict that P. perniciosus may disperse from Western Europe towards Bavaria, but a direct northward spread from Italy may be blocked by the Alps.
            Climate change alters dispersal and movement patterns of insects. Through ecological niche modelling in combination with a least-cost analysis, the authors were able to model the potential dispersal of sandflies in a small region of Europe. However, it is acknowledged that dispersal may not always correlate with model predictions, and dispersal behavior often varies between populations. In addition, human and wind influence are not taken into account into the models. Neverless, this type of modelling provides a powerful tool for detecting vector and disease prevalence. 

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