Pygeum

Abstract: Conservation priorities for Prunus africana, a tree species found across Afromontane regions, which is of great commercial interest internationally and of local value for rural communities, were defined with the aid of spatial analyses applied to a set of georeferenced molecular marker data (chloroplast and nuclear microsatellites) from 32 populations in 9 African countries. Two approaches for the selection of priority populations for conservation were used, differing in the way they optimize representation of intra-specific diversity of P. africana across a minimum number of populations. The first method (S1) was aimed at maximizing genetic diversity of the conservation units and their distinctiveness with regard to climatic conditions, the second method (S2) at optimizing representativeness of the genetic diversity found throughout the species’ range. Populations in East African countries (especially Kenya and Tanzania) were found to be of great conservation value, as suggested by previous findings. These populations are complemented by those in Madagascar and Cameroon. The combination of the two methods for prioritization led to the identification of a set of 6 priority populations. The potential distribution of P. africana was then modeled based on a dataset of 1,500 georeferenced observations. This enabled an assessment of whether the priority populations identified are exposed to threats from agricultural expansion and climate change, and whether they are located within the boundaries of protected areas. The range of the species has been affected by past climate change and the modeled distribution of P. africana indicates that the species is likely to be negatively affected in future, with an expected decrease in distribution by 2050. Based on these insights, further research at the regional and national scale is recommended, in order to strengthen P. africana conservation efforts.

Abstract: The present study was originally intended to be a taxonomic revision of the genus Pygeum (Rosaceae). This genus was always considered to be closely related to, but different from Prunus. However, the delimitation of Pygeum against Prunus subg. Laurocerasus appeared to be extremely difficult, and after careful consideration I was compelled to reduce Pygeum to Prunus. This reduction is the most radical taxonomic novelty in the present paper (Chapter 3). A new subdivision of subg. Laurocerasus, now enriched with Pygeum, was inevitable. Three sections are distinguished here, viz.: a. sect. Laurocerasus, containing the Eurasian and tropical Asiatic species which were already considered by older authors to belong to the (sub)genus Laurocerasus, and moreover the two African species of the former genus Pygeum; b. a still unnamed section containing the tropical and subtropical American species of the subgenus; c. sect. Mesopygeum, containing the large majority of the species of the former genus Pygeum.