Dr. Tiago Vieira
HUH Research Fellow
Harvard University
Title: Systematics of Prosthechea (Laeliinae, Orchidaceae): reassessing the lumper-splitter debate and shedding light on the evolution of this Neotropical lineage through a molecular phylogeny
Abstract:
Prosthechea (Laeliinae, Orchidaceae) is a Neotropical genus of Orchidaceae comprising ca. 120 spp. Its current – and broader – circumscription represents a reconsideration of an old name to accommodate species previously placed in Encyclia subgen. Osmophytum. However, after the reconsideration, other classifications have been proposed splitting the group into smaller genera, such as Anacheilium, Euchile, Hormidium, Panarica, Pollardia, Prosthechea s.s., and Pseudencyclia. This scenario brings taxonomic confusion, with botanists and orchid cultivators swinging between different classifications, and there is still some debate concerning what would be the more appropriate way to circumscribe that group of species at the generic level. In this work, a phylogeny based on nrITS and plastid DNA sequences is presented, including 80 spp. of the genus and 12 spp. of related genera, using Bayesian inference and Maximum Parsimony. The results corroborate the monophyly of the lineage corresponding to a broad circumscription of Prosthechea. Splitting Prosthechea into smaller genera is not supported by our phylogeny, and non-monophyly also hinders the proposal of a comprehensive infrageneric classification. Ancestral state reconstructions point to independent evolution of non-resupination and other morphological traits previously considered of taxonomic value in different lineages within Prosthechea. The phylogenetic relationships recovered reflect better biogeographic patterns rather than previously proposed morphological affinities, due to homoplasy in floral traits. Conflicts between nuclear and plastid data were detected, although the results were not conclusive between incomplete lineage sorting or reticulate evolution as the reason. A preliminary biogeographic analysis suggests that Prosthechea had originated in Mexico during the Late Miocene (~7.64 Mya), dispersing towards South America afterward. Join via Zoom livestream: https://harvard.zoom.us/meeting/register/tJcuf-uqpj4oE9YbvUjBJj-c0AyiB6-C5Poe (registration required)
