Alejandro has analysed the importance of genetic variation at the Major Histocompatibility Complex (genes of immune responses) for successful invasion by exotic organisms: are individuals already selected to be more resistant to diseases before they are introduced to novel ranges? We studied this in two species of weaverbird from Africa. He also developed a novel technique for molecular sexing in the field within two hours (!), resulting in a patent application and two major papers (one in Molecular Ecology Resources here). Alejandro´s lab skills were a great asset to the group. (One-year contract funded by University Pablo de Olavide).