Approximate Bayesian Computation on Ficus craterostoma genetic variation to understand the history of forests in South Africa

Abstract

Over the past 2.58 million years, recurring glaciation cycles have influenced the distribution and demography of forest in South Africa. These cycles may have led to fluctuations in forest population number and size due to climatic factors. This is because one hypothesis for forest distribution in South Africa is that forests can only grow under specific climatic conditions that limit their distribution. In addition, it has been proposed that forests can only persist in areas protected from natural fires. Ficus craterostoma is a fig tree species confined to forests that should have experienced climatic and fire driven range limitations and potentially recent anthropogenic changes to its distribution. Anthropogenic events like the Bantu-speaking migration (approximately 800-500 YA) and the arrival of European settlers (around 400-300 YA) could have caused forests to contract due to exploitation. The recent history of this species and forests in general remains largely unexplored. Approximate Bayesian Computation analysis revealed that 1) severe bottlenecks occurred towards the end of last glacial maximum (LGM), 2) significant forest expansion was unlikely following the LGM and that 3) there was no human-induced effect on forests. Rather, after the historical bottleneck, forest populations recovered slightly but were unable to return to their once large populations. Therefore, I infer that fire and climate have limited forests in South Africa.