The story behind Africa’s rainforests
The tropical rainforests of West and Central Africa are one of the most biodiverse ecosystems on Earth but are under serious threat from population growth, agriculture and unsustainable forestry. The race is on therefore to understand the evolutionary history and ecological processes behind this vast diversity of life before it is lost forever. Botanical collections kept in Europe’s museums and scientific institutes are a valuable research tool, covering areas of tropical Africa that are currently difficult to access. However, these samples that were collected during colonial times cannot be studied using conventional molecular techniques, which are only suitable for modern samples with well-preserved DNA. The EU-funded AGORA (Ancient genomics of rainforests) project was established to investigate novel methods for investigating these collections. The initiative focused in particular on eight rainforest trees from Central Africa, using a combination of state-of-the-art genomics and techniques for ancient DNA to reconstruct the natural history of the rainforest ecosystem. Results indicated barriers in the past to gene flow and a history of fragmentation of the rainforest. This corresponded with the climatic history of tropical Africa during the penultimate and last Ice Ages. At this time dry conditions led to the contraction of rainforests in favour of savannah grasslands, and the survival of rain forest species in a few refugia. AGORA provided new techniques and fresh insights into the evolutionary history of the rainforests of West and Central Africa. The locations of several refuge areas in Africa, previously proposed using the rate of endemic species as a basis, have been confirmed using novel population genomic analyses.
Keywords
Tropical rainforest, West Africa, Central Africa, botanical collections, AGORA, genomics, Ice Age, refugia
