Cyperus esculentus (yellow nutsedge or tiger nut) is widespread in tropical and temperate zones and is also present in cooler regions. It is used as a crop, but also grows wild as a weed and is very invasive. De Castro et al. investigate the phylogenetic position and biogeography of C. esculentus and detect two types of ribotypes in nrDNA with an evident geographical segregation into an Old World group and a polymorphic New World group. On the basis of the results, a hypothesis on the origin and phylogeography of this species is proposed, which suggests that C. esculentus probably originated in the late Cenozoic in Africa and reached the Americas repeatedly, independently of Columbian exchanges.