The role of Quaternary glaciations in shaping biogeographic patterns in a recently evolved clade of South American epiphytic orchids

Abstract

To contribute to what is known about involvement of vegetation dynamics in Neotropical speciation, we used the Epidendrum latilabre complex, a taxonomically well-defined species group, to investigate past connections between Amazonian (AM) and Atlantic (AF) forests and address the following topics: (1) divergence times between sister species currently distributed in AM and AF; (2) distribution patterns of ancestral species of the E. latilabre complex and (3) potential routes connecting ancestral ranges between AM and AF. We developed a robust phylogenetic estimate for species of the E. latilabre complex by sequencing two nuclear and six plastid loci. Then, we combined divergence time estimation, ancestral range reconstruction and ecological niche modelling. Our biogeographic reconstruction exhibits a complex pattern of connections among tropical forests east of the Andes in South America. The AM and AF species of the E. latilabre complex are intermixed in the results, and climatic shifts during the Pleistocene (Chibanian) are suggested here as a major force promoting speciation. Sister species tend to be ecologically distinct in their climate niche spaces, and vicariance and peripheral isolation are reconstructed as the main drivers of speciation. There is evidence to suggest that the south-east/north-west bridge and the northern/north-eastern coastal route have been occupied by the ancestors of the E. latilabre complex, and alternative routes across the South American dry diagonal were unlikely. Further studies on Neotropical epiphytic taxa are still necessary for understanding the dynamics of historical connections between AM and AF.