Résumé
The world’s second largest expanse of tropical rain forest is in Central
Africa and it harbours enormous species diversity. Population genetic
studies have consistently revealed significant structure across central
African rain forest plants, in particular a North-South genetic
discontinuity around the equatorial line, in a continuous expanse of rain
forest but where a climatic inversion is documented. Here, we took a
phylogeographic approach by sequencing 351 nuclear markers in 112
individuals across the distribution of the African rain forest tree
species Annickia affinis (Annonaceae). We showed for the first time that
the North-South divide is the result of a single, major colonisation event
across the climatic inversion from an ancestral population located in
Gabon. We suggested that differences in ecological niche of populations
located on either side of this inversion may have contributed to this
phylogenetic discontinuity. We found evidence for inland dispersal,
predominantly in northern areas, and variable demographic histories among
genetic clusters, indicating that populations responded differently to
past climate change. We show how newly-developed genomic tools can provide
invaluable insights into our understanding of tropical rain forest
evolutionary dynamics.