Biogeografia histórica de Dracula luer (Pleurothallidinae-Orchidaceae)

Abstract

The uplift of the Andes Mountains altered the geological formation of South America, contributing to the emergence of specific habitats and the isolation of species. Currently, the Andes Mountains are considered one of the largest biodiversity hotspots in the world. Despite being considered a biogeographic barrier, for angiosperms in general, due to their size, studies indicate that the Andes Mountains act as a semi-permeable barrier for organisms with epiphytic habits and shrubs with anemochory-type seed dispersion (dispersion through wind). Dracula Luer is a group of epiphytic orchids from cloud forests that occur mainly in the Andean region (ca. 90% of the 100 accepted species) with greater abundance in the countries of Colombia, Peru and Ecuador. With this study, we seek to develop a comprehensive historical biogeography study for Dracula and thus be able to investigate the area of origin of the genre, as well as its age. Furthermore, we aim to understand the patterns of trans-Andean dispersal events and the colonization of Central America and Mexico. We developed a phylogenetic reconstruction using the plastid markers matK and ycf1 and the nuclear ITS. We combine divergence time estimates and reconstruction of ancestral areas. Dracula was recovered as monophyletic with its emergence in the western Andes Mountains in the late Miocene 7.98 Mya, but with diversification beginning at 4.24 Mya. Dracula's biogeography is marked by several independent events of peripheral isolations and short- and long-distance dispersals. At least 12 dispersals occurred from the region west to the east of the Andes, and none in the opposite direction. The colonization of Central and North America occurred through at least four independent dispersal events. We conclude that Dracula's biogeographic history is complex, and that the Andes Mountains were permeable for the genre only in the West/East direction.