Consequences of Community Assembly Processes in Paleoclimate Estimation Using Angiosperm Fossil Woods

Community assembly processes (environmental filtering and limiting similarity) determine the values of quantitative functional traits within communities*The environment influences the number of viable functional strategies species might take*A strong effect of environmental filtering often results in communities having species with similar trait values and narrow functional niches*On the other hand, resource competition (i.e., limiting similarity) leads to communities with broader functional spaces and smaller niche overlap among competing species*The degree to which community assembly processes influence wood trait variation has important implications for paleoclimate estimation using fossil woods since the central tenet of the approach is environmental-driven trait convergence, which assumes a central role of environmental filtering*To infer the strength of these two community assembly forces, we used a functional diversity approach to determine how three wood anatomical traits vary in 14 extant communities (272 species) growing under different climates*We found smaller functional spaces in communities growing in dry/cool places, suggesting that trait convergence could be the result of more robust habitat filtering in these communities*A weaker environmental filtering in warm/wet environments, likely results in an amplification of other drivers that promote a higher number of hydraulic strategies through niche partition in highly structured communities*More complex ecological structures in mild, tropical places likely lead to a higher spread of wood trait values*This asymmetry in the strength of environmental filtering along climate gradients suggests that this differential strength of the trait-climate convergence should be incorporated in paleoclimate prediction models.