Uganda's endemic flora: discovery, diversity, distribution and threat status.

Threats including habitat loss and overexploitation continue to endanger plant diversity in Uganda. Heightened effort is needed to more effectively protect threatened species to ensure ecosystem service provision and support of livelihoods. One important step in this direction is to identify areas locally rich in biodiversity in general, and endemism in particular, where conservation efforts may most effectively contribute to protecting global biodiversity. We analysed data on the distribution of 4,816 known species of native vascular plants of Uganda to identify the endemic and near-endemic plant taxa. Distribution data were obtained from herbarium records and online resources and more than 5,000 occurrence points of priority plant taxa in Uganda collated in a BRAHMS database. A total of 184 endemic and near-endemic taxa of vascular plants are identified and documented, of which 52 are strict-endemic and 82 are near-endemic species, with a further 15 strict-endemic and 35 near-endemic infraspecific taxa. These together represent 3.8% of the known vascular flora of Uganda, with families including Asparagaceae, Asphodelaceae and Asteraceae contributing significantly to the endemic flora. These endemics cover a wide range of growth forms, but the majority (60%) are herbaceous whilst tree taxa contribute less than 15% of the total endemic flora. Significant spatial variation in the richness of endemic species is observed. The regions with the highest endemism are the montane areas of the Albertine Rift and of Eastern Uganda. However, as botanical inventories extend to understudied areas, we might expect that species new to science continue to be described. More than 90% of the endemic flora of Uganda has been assessed for its extinction risk, of which 58% are currently assessed as threatened (VU, EN, or CR on the IUCN Red List). The results of this study highlight the significant risk faced by plants unique to Uganda and have helped to inform the identification of Important Plant Areas as a key step towards spatial conservation prioritisation for Uganda's critical plant diversity and the ecosystem services it supports.