CONSEQUENCES OF COMMUNITY ASSEMBLY PROCESSES IN PALEOCLIMATE ESTIMATION USING ANGIOSPERM FOSSIL WOODS

Abstract

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.