On the trail of the African cherry tree

Prunus africana, better known as the African cherry, grows on the mountain slopes of sub-saharan Africa. It has a high genetic diversity that is especially prevalent in Kenya, Madagascar and Cameroon and has provided a good source of income for local farming communities due to the medicinal properties of its bark - used to treat benign prostatic hyperplasia (enlarged prostate).

Part of a project to develop sustainable ways to use Prunus africana to improve livelihoods of small-scale farmers  [1] was to undertake analyses of its genetic diversity - to develop conservation strategies and help farmers identify high quality planting stock.

The analyses showed that the highest genetic diversity both in genetic markers and bark chemistry were Kenya, Madagascar and Cameroon - showing that these areas need to be targeted as a high priority for conservation.

The analyses of leaf samples reveal a probable migration route from when the species first colonised Africa. Based on genetic markers found in the chloroplast (the part of the plant cell where photosynthesis occurs), it appears that all populations in continental Africa flowed from Ethiopia before splitting in Kenya along the Rift Valley. The western branch migrated to Cameroon and Nigeria and an eastern branch moved south to the tip of South Africa. 

The populations on Madagascar have completely different markers and may have originated from a prior Asian source, independently of African colonization. Interestingly, the populations in western Kenya are more similar to those in Cameroon than to eastern Kenyan sources implying that the split along the Great Rift was long standing and constituted a complete barrier to gene flow for many thousands of years.  This valuable information helps us to understand the path of genetic diversity to prioritise conservation action.