Beyond the Highlands: Climate Drives Evolutionary Connections Between Ancient Neotropical Mountains and Lowland Biomes

The assembly of montane plant communities through time is underlain by historical and abiotic factors. However, theextent of evolutionary connectivity between ancient highland ecosystems and surrounding lowlands remains unclear. Here,we investigate the evolutionary connections between the campos rupestres, a hyperdiverse and fragmented montane vegetationcomplex in eastern South America, and lowland biomes surrounding it: savannas, rainforests and seasonally dry tropical forests. Using phylogenetic beta diversity analyses for 13 angiosperm clades, we assess the degree of lineage dissimilaritybetween campos rupestres subregions and adjacent biomes. We also apply generalised dissimilarity modelling to determine therole of climate, soil and geographic distance in shaping spatial patterns of phylogenetic composition. Our results reveal high lineage permeability between campos rupestres and surrounding biomes, with lineage sharinglargely reflecting biome adjacency. This pattern is mainly driven by shared climatic conditions, which are the strongest predic-tors of phylogenetic dissimilarity. We highlight the importance of lineage exchange between lowland and montane environments for the as-sembly of highland floras. By showing that lineage movements across biome boundaries have been common over time and acrossspatial scales, our study challenges the idea that ancient Neotropical mountains are isolated sky-islands. Instead, we emphasisethe dynamic nature of montane plant diversity and the pivotal role of climate in shaping evolutionary connections betweenhighlands and lowlands.