Lineage diversification and long-term persistence in the Greater Cape Floristic Region: Insights from molecular data

• The drivers of diversification operational in the GCFR are reviewed in depth. • New insights gained from Next Generation Sequence data enabled interpretation the mechanisms of evolutionary change at much shallower timescales. • Sea level fluctuations are highlighted as additional driver of diversification in unique coastal habitats. The Greater Cape Floristic Region (GCFR) is renowned for its exceptional species richness and remarkable beta diversity at fine spatial scales. This unique flora has captivated naturalists since the early 17th century colonial exploration of the region. Understanding the patterns and processes underlying this diversity has been the focus of over a century of evolutionary research, and recent advances in next-generation DNA sequencing have further enhanced our understanding of lineage diversification at very shallow timescales. Our review of these processes confirms that multiple interacting drivers of speciation have produced the extraordinary biodiversity of the GCFR. Key drivers of speciation include high environmental heterogeneity, periodic fire regimes, range-limited dispersal, pollinator-driven divergence, and phenological shifts. Another potentially significant yet underexplored driver is the role of Pleistocene sea-level fluctuations, which we propose have played a critical role in promoting recent divergence among coastal endemic floras. In addition to these drivers of speciation, the maintenance of biodiversity in the GCFR has been facilitated by long-term climatic buffering, and niche partitioning supported by a suite of plant ecophysiological trait specialisations.