Lianas (woody vines) comprise 10-40% of the individuals and species of tropical forests. They proliferate in response to global change and differentially reduce the survival growth and reproduction of tree species. Indeed it has been proposed that lianas alter the competitive balance among tree species and even that there are trees with adaptations to avoid and shed lianas. However many evidences suggest that lianas also have neutral and positive effects on trees and thus a multiple linear regression model is formulated on the role of lianas on tree communities. Such a model is an expansion of the differential hypothesis on the effect of lianas on trees. Liana’s role in structuring tree communities can be reduced and diffused among tree species due to the diffuse non-predictable associations among species of lianas and trees and to the rapid switch of such associations in time and space. That is consistent with evolutionary studies showing that lianas are not a major selective pressure favoring adaptations of trees to avoid and shed them; such characteristics have other functions. Further studies combining both Ecology and Evolution may better explain the relationships between the two main components of the woody flora of tropical forests: lianas and trees.