Disentangling the role of migration, human transport and Wolbachia infection in the global invasion of a disease vector, the Asian Tiger mosquito (Aedes albopictus), using a genomic approach.
Evolution, Anthropology
Final Report Abstract
During the course of this project I was able to obtain field-collected specimens from 37 countries worldwide, including some that have not previously been analyzed by means of next-generation sequencing markers, e.g. Cameroon. I used double digest restriction site-associated DNA sequencing. This method allows obtaining single nucleotide polymorphic sites in all sources of DNA found within a single mosquito. This includes nuclear as well as mitochondrial DNA of the study organism, but also that of organisms that live within the host, such as the symbiotic bacterium Wolbachia. One work package of the project focused on the native Asian distribution range of Aedes albopictus. Here I was able to obtain high resolution power for 15 sampled sites. I found pronounced population structure on the studied Island populations and subtle population structure in mainland Asia. Our findings suggest further that there have been two introduction events into Sri Lanka most likely at different points in time. This was previously unknown and showcases how the chosen approach successfully detects structure even at very fine temporal scales. The analysis of the global data set, work package 2, is currently underway. I was able to sample a total of 22 countries distributed throughout the range that has been invaded by this species in recent years. Unfortunately, data analysis could not be conducted at the time envisioned in the project proposal due to unforeseen difficulties that are explained in the following section. However, preliminary analysis show that we are able to successfully detect Wolbachia DNA in the sequencing reads and it is possible to determine which bacterial strain is responsible for the infection and whether this is a single or double infection. Further analysis will provide insights on the effect if the infection on Aedes albopictus dispersal. The sampling of mosquito specimen took longer than expected. Although building collaborations was straight forward more collections of fresh specimen needed to be undertaken than anticipated. In order to speed up the sequencing itself by filling an entire flow cell, I decided to finish the library preparation for all samples prior to sending the samples to the sequencing facility. Unfortunately, the sample labels got mixed up at the sequencing facility which seriously delayed the analysis. It took some months to figure out what the error was. Currently we are still in the process of finding the correct labels for each sample. This step is crucial in order to be able to sort the sequences belonging to each individual mosquito sample and thus correctly infer the population origin.
