Networks of epiphytic orchids and host trees in Brazilian gallery forests

Species interactions have been recently depicted its networks. in which each species is connected to one, or more other species in binary interaction matrices. Forty networks of epiphytic orchid and host tree species were assessed in Brazilian gallery forests. The nestedness of the networks was estimated with the NODF index and the significance was tested with null models. The phylogenetic structure of the network was also assessed. by searching for phylogenetic signals in the number of interactions and in the similarity of interacting species. In total 105 orchid species and 132 host tree species were sampled. A nested pattern in all orchid-host tree networks was found. However, phylogenetic signals were not observed. The results support, that the host specificity of orchids is small and most of the interactions occur among generalist orchids and generalist host trees. while the concept of species-specificity can thus be rejected. the extreme alternative - that interacting orchids and host trees arc not a random subset of the regional species pool - cart be dismissed as well. However. factors other than phylogenetic history may structure interaction networks of epiphytic orchids and host trees.