Maianne, M. | Search bioRxiv

bioRxiv2026

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

AimThe assembly of montane plant communities through time is underlain by historical and abiotic factors. However, the extent 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 vegetation complex in eastern South America, and lowland biomes surrounding it: savannas, rainforests, and seasonally dry tropical forests. LocationEastern South America. Time periodCenozoic. Major taxa studiedFlowering plants. MethodsUsing phylogenetic beta diversity analyses for 13 angiosperm clades, we assess the degree of lineage dissimilarity between campos rupestres subregions and adjacent biomes. We also apply generalized dissimilarity modeling to determine the role of climate, soil, and geographic distance in shaping spatial patterns of phylogenetic composition. ResultsOur results reveal high lineage permeability between campos rupestres and surrounding biomes, with lineage sharing largely reflecting biome adjacency. This pattern is mainly driven by shared climatic conditions, which are the strongest predictors of phylogenetic dissimilarity. Main conclusionsWe highlight the importance of lineage exchange between lowland and montane environments for the assembly of highland floras. By showing that lineage movements across biome boundaries have been common over time and spatial scales, our study challenges the idea that ancient Neotropical mountains are isolated sky-islands. Instead, we emphasize the dynamic nature of montane plant diversity and the pivotal role of climate in shaping evolutionary connections between highlands and lowlands.

plant biology↗

bioRxiv2025

When morphology stands still: constrained floral evolution in a mega diverse legume genus

O_LIChanges in floral morphology are key for the evolutionary success of flowering plants. However, many species-rich and ecologically diverse groups show low variation in floral traits. Low morphological variation may be associated with selective pressures and constraints to changes. Nonetheless, because our understanding of floral morphological evolution is focused on plant groups with diverse and specialized floral morphology, there has been little progress in identifying factors underlying floral morphological uniformity. C_LIO_LIHerein we addressed this issue by asking whether the morphology of flowers in the mega-diverse legume genus Mimosa is shaped by constraints. By investigating patterns and processes underlying trait variation along floral whorls, we evaluated the role of development and/or function in limiting morphological change. C_LIO_LIOur results showed that floral morphology is remarkably homogeneous and likely shaped by convergent evolution. Morphological variation is unevenly distributed across floral whorls, reflecting differences in the levels of constraints. C_LIO_LIFloral morphology in Mimosa is unlikely to have been primarily driven by pollinator-mediated selection. Instead, we suggest that the development and function of flowers in the mimosoid inflorescence constrained morphological evolution in this megadiverse yet morphologically uniform group. C_LI

evolutionary biology↗