Alternative hypotheses of African rain forest origins. (A) Distribution of lowland rain forest in Africa (black) overlaid by altitudinal range (increasing altitude with darker grey). Red lines highlight the Guineo-Congolian region; the blue line highlights the East African region. (B) Phylogenetic tree expected from a single break-up scenario. (C) Phylogenetic tree expected from multiple break-ups at significantly different times scenario. Open circles indicate West-Central/East splits.