Project Summary/Abstract We have recently shown that the ancestors of all Aedes aegypti populations in both sub-Saharan Africa as well as around the world presently reside on islands in the Southwest Indian Ocean (SWIO) including Madagascar. These islands gave rise to continental African Ae. aegypti formosus no earlier than about 100,000 years ago. We propose multidisciplinary studies on SWIO populations of Ae. aegypti along with its close relatives, Ae. mascarensis and Ae. pia. This will include population genetics, phylogenetics/phylogeography, vector competence, blood meal analyses, and characterization of the virome of field-caught females. We address question such as: Are the ancestors that gave rise to Ae. aegypti s.s. capable of transmitting the same viruses that cause human diseases? Are these mosquitoes carrying the same viruses in the field and/or do they harbor novel undescribed arboviruses? What are the sources of their blood meals? Where do they breed? Population genetics and phylogenetic preliminary work have already identified candidates for new undescribed species and we suspect more cryptic taxa will be found. We propose to assemble complete genomes for the most informative populations/taxa that will allow comparative studies as well as inference of the ancestral genome of Ae. aegypti s.s., a fundamental resource for analysis of a plethora of genomics studies ongoing in laboratories around the world.