Does phylogeny have a role in the liana-phorophyte interaction in tropical forests?

Abstract

We assessed the influence of species phylogenetic relatedness on the interaction between woody climbing plants (lianas) and their host trees (phorophytes). Considering that closely related species tend to have similar niches, we expected (1) closely related lianas to co-occur in similar phorophyte sets and (2) original lianas (phylogenetically distinct lianas with unique set of features) to occur on distinct phorophyte sets. We sampled three highly diverse forest sites in SE Brazil (a tropical rainforest, a savanna woodland and a tropical semideciduous forest), and sought for (1) a phylogenetic signal in liana climbing traits; (2) a phylogenetic signal in the liana-phorophyte interaction by testing the correlation between (a) phylogenetic distances and similarity of interacting species sets and (b) the species phylogenetic originality and the number of their interactions; and (3) a positive relationship between phylogenetic originality and the specificity of liana-phorophyte interactions. We found a phylogenetic signal in climbing systems of liana species. In the semideciduous forest, we observed that closely related lianas share similar phorophyte sets, and original lianas occur on a small number of phorophyte species. However, when we evaluated the interactions of species with high originality, we found an opposing pattern in forests and savanna. In forests, the phylogenetically original liana species co-occurred more frequently with very distinct phorophyte sets; whereas in the savanna woodland, the phylogenetically original liana species co-occurred conversely with common phorophyte sets. We argued that environmental differences in forests and savannas could have mediated different tree morphological traits, such as bark characteristics, which might structure different liana-phorophyte interactions.