Inferring the diversification of the epiphytic fern genus Serpocaulon (Polypodiaceae) in South America using chloroplast sequences and amplified fragment length polymorphisms

In this study, we infer the phylogeny of the recently described epiphytic fern genus Serpocaulon. Four regions of the plastid genome were sequenced for 68 samples, representing 31 of ca. 40 currently accepted species of this genus. The reconstructed phylogeny supports most of the previously proposed clades, but more exhaustive studies are needed to improve species delimitation in several terminal clades. A further objective of this study was to determine the utility of amplified fragment length polymorphism (AFLP) data to study the diversification of species complexes. Independent analyses of data sets based on chloroplast DNA sequences or AFLPs resulted in phylogenetic trees with similar topologies, but showed also some notable differences. We present an explicit hypothesis of the biogeographic history of Serpocaulon. All reconstructed phylogenies suggest an origin of this genus in the Bolivian–Brazilian region and indicate a major role of the Bolivian Andes as a stepping-stone in the colonization of northern regions of the Andes. The majority of the extant species diversity of this almost exclusively epiphytic fern clade is likely the result of an adaptive radiation that was triggered by the colonization of Andean mountain forest habitats (above 2,000 m). This is the first report of a Bolivian origin of fern diversification in Andean mountain habitats using phylogenetic evidence.