Abstract

Although, the probability of an alien plant species to become invasive in natural or semi-natural habitats is relatively low, the introduction of new taxa should always be regarded as a sensitive issue because the effects of an insertion of an invasive species are likely to be prohibitive as well as external. Ideally, plant species with an invasive potential should not be allowed to enter a country and, if they do, the next best scenario is early detection and eradication. Unfortunately, in Rwanda, despite its location in the Albertine Rift, a biodiversity hotspot with many endemic and endangered species, little is known about the status of introduced taxa. In this article, we combine the insight from library resources, herbarium records and vegetation surveys to document the status of an introduced species, Mimosa pigra L. The results comprise evidence that this species has reached the invasive status in Rwanda and support the plea that it be officially listed as such. We suggest that Egypt through Uganda may have been the primary source of M. pigra L. propagules that first infested Rwanda through the Akagera-Nyabarongo river system, earlier than Mid-19^th century. We presume that under the shadow of its non-specific Kinyarwanda name ‘u-mu-gey-o’, it was able to spread undisturbed and invade Rwanda’s central and eastern floodplains before scientists could take notice of its true identity.

Key words: Mimosa, invasive, Nyabarongo, floodplain, Umugeyo, infestation, range.