Incorporating phylogeny into comparisons between lianas and trees

Background/Question/Methods

Lianas are a unique, species rich growth form that reach peak abundance and diversity in tropical forests and recent evidence indicates that they are increasing in abundance for reasons that are not yet clear.  Increases in lianas relative to trees may have importation implications for carbon storage of tropical forests.  Multiple studies have shown that lianas have greater physiological rates and more efficient resource capturing tissues compared to trees, but these comparisons have neglected to consider the relatedness of the species being compared.  This is especially important when making comparisons between trees and lianas because the liana habit evolved independently in numerous plant families.  Thus it is not known whether differences in physiology and leaf traits between trees and lianas are due to characteristics inherent to the climbing growth form or due to relatedness.  We test the hypothesis that differences in physiology and leaf traits between trees and lianas are caused by growth form differences rather than relatedness.  To test this hypothesis, we compared leaf and photosynthetic traits for over 400 species of trees and lianas using standard statistical methods as well as phylogenetic comparative methods. 

Results/Conclusions

Our preliminary results show that lianas had higher photosynthetic rates, leaf nitrogen and lower leaf mass area compared to trees.  Phylogenetic analyses showed that none of these traits showed a significant phylogenetic signal.  These results suggest that lianas have greater rates of photosynthetic physiology compared to trees that is independent of phylogenetic relatedness and this may explain their successful competition with trees and among contrasting habitats.