Master Thesis

Wind speed predicts the non-occurrences of the Asian Tiger mosquito Aedes albopictus in Europe and limits the contribution of relevant temperature and precipitation parameters.

Emmanuel Adeleke (10/2020-04/2021)

Support: Stephanie Thomas, Carl Beierkuhnlein

Objectives: Recent ecological niche models (ENMs) have identified regions within the climatic niche of the Asian tiger mosquito (Aedes albopictus) where there are non-occurrences of the vector mosquito. The potential of wind speed to predict these non-occurrences in an ecological niche model (ENM) implemented to model the distribution of this highly effective invasive mosquito vector has been largely unknown. Therefore, the current study aims to evaluate the potential of wind speed as a predictor of these non-occurrences of Ae. albopictus in Europe. The study examines the relationship between high wind speeds and the non-occurrences of the vector mosquito within its climatic niche in Europe. Methods: We implemented an ENM for Ae. albopictus using the maximum entropy (MaxEnt) modelling approach. The model is trained with the occurrence records of Ae. albopictus and relevant environmental parameters consisting of temperature-related and moisture-related bioclimatic variables. A student two sample t-test was performed to test for significant differences in average wind speeds between areas of occurrences and non-occurrences of Ae. albopictus in Europe. Other statistical tests such as a multiple linear regression analysis and a test of average marginal effects were also performed. Several GIS methods for analysing geospatial datasets including buffer analysis, raster extraction, and spatial overlay methods were also performed. Results: Wind speed showed insignificant model training gains and therefore was not included as an explanatory parameter of the MaxEnt model. Annual temperature and mean temperature of the warmest quarter were the most important variables contributing to the performance of the MaxEnt model. Results showed that the relative contributions of these parameters to predictions of Ae. albopictus occurrences is limited by interactions with wind speed. Furthermore, a significant difference exists in average wind speeds between areas of occurrences and non-occurrences of Ae. albopictus in Europe. We observed that areas of Ae. albopictus occurrences tend to have lower average wind speeds than their areas of non-occurrences. Conclusions: We have identified the potential of wind speed to predict the non-occurrences of Ae. albopictus in Europe. This study provides an explanation for the recently reported phenomenon of the non-occurrences of the mosquito species in areas climatically suitable for its distribution. Our results provide strong evidence that high wind speeds are a major factor contributing to these non-occurrences. This study also identifies the importance of temperature and moisture-related parameters in predicting the occurrences of Ae. albopictus. We recommend that future attempts to determine explanatory parameters for Ae. albopictus distribution in Europe should place more emphasis on temperature and moisture-related parameters and should consider wind speed parameters only as limiting environmental factors.