Intercontinental divergence in the climate envelope of major plant biomes

Aim: Convergent evolution and environmental filtering are assumed to often result in deterministic patterns of vegetation structure and function in relation to prevailing environmental conditions regardless of differences in evolutionary history among regions. We systematically evaluate the degree to which biomes located in different biogeographic realms converge in environmental space; identifying globally uniform entities and those diverging systematically among realms. Location: Global. Methods: Two global biome distribution maps constructed using contrasting approaches are used to evaluate convergence in the environmental space occupied by biomes across biogeographic realms. Environmental conditions are summarized using nine climatic and two edaphic variables known to directly influence plant distributions. Biome maps are analysed accounting for differences in the availability of environments among realms. Results: The same biome located in two different realms often overlaps no more in environmental space than two altogether different biomes, with the average overlap on the two biome maps calculated using Schoener's D metric only 0.42 and 0.36. This suggests that the coarse structural and phenological characteristics used to define biomes conceal important differences in plant functioning and responses to environmental drivers. Nonetheless, some biomes, in particular savannas and boreal forests, show high overlap among realms. Others, like mediterranean-type ecosystems and treeless biomes, often occur in vastly different regions of environmental space. Within most biomes though overlap varies greatly depending on the specific realms being compared, with historical biogeography and evolutionary history helping to explain this variation. Main conclusions: Biomes often occur under different environmental conditions when comparing regions with distinct evolutionary and environmental histories. The biome concept and efforts to model current and future vegetation patterns needs to be adapted to account for the role of history in determining how vegetation responds to environmental drivers and disturbance.