Molecular Phylogeny, Evolution, and Biogeography of South American Epiphytic Cacti

Abstract

Epiphytes represent an important element of the tropical flora and are widely distributed across vascular plants. Despite this diversity, however, little is yet known of the evolutionary history, habitat preference, morphological diversity, and biogeographical patterns of epiphytes as a whole. Approximately 10% of cacti are epiphytes inhabiting humid regions, and Rhipsalis represents the largest genus of these. Here we reconstruct relationships among species of the genus Rhipsalis on the basis of plastid and nuclear DNA markers (trnQ-rps16, rpl32-trnL, psbA-trnH, internal transcribed spacers, and malate synthase) and use them as a basis to study the evolution of habit, key morphological features, and the biogeographical history of the genus. Rhipsalis is highly supported as monophyletic, presenting three main lineages. Two lineages are marked by unique floral morphologies and one presents an exclusive stem-shape morphology. In spite of this, neither of these features seems to have been associated with small-scale habit transitions or large-scale transitions through different biogeographical regions. Several lineages of the genus seem to have originated in coastal Brazil and subsequently occupied other tropical forests in South America, North America, Africa, and Asia. These events occurred in relatively recent times, with most of them taking place on terminal branches, thus suggesting recent associations between South American epiphytic flora.