Martinez-Cabrera, H. I. | Search bioRxiv

bioRxiv2022

Vessel wall reinforcement metrics as drought resistance indicators in angiosperm fossil wood assemblages

BackgroundPlant ecologists have developed methods to measure xylem drought resistance but these cannot be used in fossil woods. There is, however, one anatomical trait highly correlated with cavitation resistance: the squared vessel-wall thickness-to-span ratio ((t/b)2h). This metric though, could be in many cases impractical to measure in fossil samples because they often are small and sample sizes are seldom reached. Questionsare there alternative anatomical metrics that could be used instead of (t/b)2h to infer drought resistance of fossil wood assemblages? Study site and dates279 species belonging to 14 extant communities from North and South America. Three fossil wood floras from the Oligocene and Miocene of Mexico. MethodsWe calculated three alternative wall reinforcement metrics to determine their relationship with (t/b)2h and drought resistance. These are based on vessel diameter and vessel wall thickness. ResultsWe found that one of the alternative metrics ((t/b)2hydraulic mean) could potentially be used instead of (t/b)2h. The widely measured vessel wall-to-lumen ratio (VWLR), was the closest related to climate, and thus helpful in identifying broad precipitation differences among floras. VWLR and (t/b)2h might be describing slightly different ecological axes of ecological variation, with the latter associated with investment in support tissue, in addition to water availability alone. ConclusionsSome of the alternative metrics we explored can be used, in combination with other functional traits, to better describe fossil forest functional strategies.

paleontology↗

bioRxiv2019

Hydraulic diversity of El Cien Formation (Baja California Sur, Mexico) and the consequences of functional diversity in paleoclimate estimation using fossil wood

ABSTRACTCommunity assembly processes, environmental filtering and limiting similarity, determine functional traits values within communities. Because environment influences the number of viable functional strategies species might take, a strong effect of environmental filter often results in communities having species with similar trait values and narrow functional niches. On the other hand, limiting similarity lead to communities with broader functional spaces. The degree to community assembly processes influence wood trait variation has important implications for paleoclimate estimation using fossil wood since the main tenet of the approach is environmental driven trait convergence, and assumes a central role of environmental filtering. We used functional diversity (FD) to determine how three wood anatomical traits vary in 14 extant communities (272 species) growing under different climate regimes, and inferred the prevalence of environmental filtering/limiting similarity. We also calculated FD metrics for the El Cien Formation fossil woods and discussed the results in light of the current knowledge of the flora. We found lower anatomical diversity in communities growing in dry/cool places (smaller functional spaces and lower abundance of trait combinations), suggesting that strong wood anatomical trait convergence could be the result of stronger habitat filtering in these communities. A lower strength of environmental filter in warm/wet environments, likely results in an amplification of the role of other drivers that promote 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 filter along climate gradients, suggest that the imbalances in strength of the trait-climate convergence, should be incorporated in paleoclimate prediction models. FD approach can be used to recognize promising traits with narrow niches along climate gradients, and therefore a constant effect of environmental filter.View Full Text

paleontology↗