The phylogenetic position of Postias.l. (Polyporales, Basidiomycota) from Patagonia, Argentina

We investigated the phylogenetic relationships of Postiaspecies from Patagonia with rDNA ITS and LSU sequences, together with morphological, cultural and biological features. All species in the genus were included in a “Postia clade” irrespective of whether their spores were thin- or thick-walled. This clade is characterized by tetrapolar mating, a normal nuclear behavior, metachromatic generative hyphae and absence of fiber hyphae in culture. One subclade merged the austral taxa P. pelliculosaand P. punctata, but otherwise no distinct relationships were found regarding spore shape, spore wall thickness and geographical distribution of taxa. The austral P. venataand the endemic P. carbophila, with thin-walled basidiospores, occupied variable positions in both analyses. Postia caesiafrom Patagonia grouped within the P. caesiaspecies complex but on a separate branch. In contrast, P. rennyiand P. balsameafrom Patagonia corresponded well with strains from other geographic areas. The two austral species in Ryvardenia, R. cretaceaand R. campyla, characterized by non-metachromatic hyphae, bipolar mating and an astatocoenocytic nuclear behavior, formed an independent subclade among the dimitic genera of the “Antrodia clade”, far from other Postiataxa within which they had been placed previously, supporting their inclusion in a genus of their own. Postia carbophilagrouped with other Postiaspecies and not with Postia(Rhodonia) placentaas suggested previously on the basis of morphological comparisons. Instead, the latter species grouped with taxa in the dimitic genus Amyloporiawith which it shares heterocytic nuclear behavior. A separation between specimens of Postia pelliculosaand Ryvardenia cretaceafrom either side of the Pacific (i.e. SE Australia/New Zealand and S Argentina/S Chile) suggests they could be considered different at the species level from a phylogenetic point of view.