Diversity of foliicolous lichens in isolated montane rainforests (Brejos) of northeastern Brazil and their biogeography in a neotropical context

Foliicolous lichenized fungi (FLF) are widely distributed in tropical forests. The Brazilian Atlantic rainforest, one of the most diverse rainforest biomes, has multiple phyto-physiognomies. Montane forest fragments or forest refuges, so-called "Brejos," are located within the semiarid Caatinga in Northeast Brazil. Our objective was to determine the FLF diversity within five Brejos and to analyze their biogeographic affinities within the Neotropics. The FLF biota of the Brejos was compared with that of 21 sites belonging to seven other rainforest biomes, ranging from the Atlantic rainforest in Argentina, to montane rainforests in Ecuador, to the Amazonia basin, and rainforests in Central America. One hundred and fifty-six species were identified in the Brejos. This biota is most similar to that of the Atlantic rainforest and eastern Amazonia, while that of western Amazonia is more similar to that of the Andes and rainforests in Central America (Choco). Multiple species identified in the Brejos have a wide distribution in tropical America, and only 11 are potentially endemic. Few other species have also a restricted distribution. The FLF biota of the Choco and western Amazon is substantially richer than that of eastern Amazon, the Atlantic rainforest and the Brejos. This suggests that the biota of the latter areas is largely a depauperate subset of the Choco and the western Amazon region. We argue that the major differences between the two large regions are related to the Pleistocene and Pliocene, when paleoclimatic and geological changes caused the isolation of the Brejos and the temporary fragmentation particularly of eastern Amazonia.