My research concerns systematics, phylogeny and biogeography of flowering plants, with a special focus on plants in the Horn of Africa region. One of the ongoing projects concerns the mapping of distributions of all tree species in this region. Otherwise we have a taxonomic focus particularly on legumes (Fabaceae) and on the order Caryophyllales. We pay special attention to patterns of endemism and to groups with large disjunctions in their distributions, such as the trans-Atlantic disjunctions that are being found in a growing number of plant groups.