Phylogeny of the Gyalectales and Ostropales (Ascomycota, Fungi): among and within order relationships based on nuclear ribosomal RNA small and large subunits.

Despite various morphological and anatomical similarities, the two orders Gyalectales (lichenized ascomycetes) and Ostropales (lichenized and non-lichenized ascomycetes) have been considered to be distantly related to each other and their position within the Ascomycota was unsettled. To estimate relationships within these groups and their respective phylogenenetic placement within the Ascomycota, we analyzed DNA sequences from the nuclear small and large subunit ribosomal RNA genes using Maximum Parsimony, Maximum Likelihood, and Bayesian statistics with Markov chain Monte Carlo algorithms. Support for internal branches estimated with bootstrap was compared to Bayesian posterior probabilities. We report here that the Ostropales, in their current circumscription, are paraphyletic, and that the Ostropales s.l. include the Gyalectales and Trapeliaceae. The Unitunicate Ascohymenials are redelineated to include the Ostropales s.l., as defined here, and the Baeomycetaceae. Dimerella and Coenogonium are congeneric, and Petractis thelotremella and P. hypoleuca are reunited with members of the genus Gyalecta. In addition to requiring less computational time, Bayesian inference of phylogeny recovered the same topology as a conventional heuristic search using Maximum Likelihood as the optimization criterion and seems superior to bootstrapping in estimating support for short internal branches.