No one-size-fits-all: Both general and particular processes shaped the mega-diverse flora of Eastern South American mountains

Aim: The astonishing diversity of ancient mountains was likely shaped by multiple parallel evolutionary processes. However, there is an ongoing debate on what were the main processes driving the assembly of campos rupestres, the mega-diverse flora of Eastern South American mountains. Although the ancient nature of these mountains suggests their flora should be composed by relatively older lineages, they harbour a number of recently diverged clades. Whilst this contradiction could be explained by a spatial compartmentalisation of community assembly processes across the heterogeneous montane landscapes, little is known about the distribution of old and recent lineages in this vegetation. To better understand plant evolution in ancient mountains, we tested if the campos rupestres are mainly composed by relatively old or recent lineages and if angiosperm diversity is geographically structured using analyses of diversity and endemism. Location: Eastern South America. Time period: Oligocene/Miocene to the present. Major taxa studied: Flowering plants. Methods: To answer our questions, we used analyses of diversity and endemism for 10% of the campos rupestres flora. We obtained distribution data from online databases, and well-sampled phylogenetic hypothesis from the literature. With these datasets, we estimated alpha and beta metrics of taxonomic and phylogenetic diversity, and conducted categorical analyses of neo- and paleo-endemism. Results: We found phylogenetic overdispersion predominates in the campos rupestres. However, this general pattern is permeated by both lineage- and site-specific phylogenetic clustering, suggesting that recent diversification events depend on particular regional conditions and on the overall maintenance of old lineages. Although endemism patterns vary among different campos rupestres sites, paleo-endemism is widespread and particularly prominent where phylogenetic overdispersion is evident. Moreover, phylogenetic composition indicates variable past spatial connections across different sites, taxonomic composition is highly geographically structured and seems to be influenced by the vegetation surrounding the campos rupestres and/or by abiotic conditions. Main conclusions: Our results reinforce the idiosyncratic nature of diversification patterns in ancient mountains and suggest that old, climatically buffered, infertile montane ecosystems not only include both relatively old and recent lineages, but that recent diversification is lineage and spatially dependent. ### Competing Interest Statement The authors have declared no competing interest.