Revisiting the secotioid and gasteroid Cortinarius species from Patagonia

Abstract

The diversity of secotioid taxa within Cortinarius in the Nothofagaceae forests of Patagonia has drawn attention of mycologists during the last century. In the Patagonian region of Argentina and Chile Cortinarius is among the most diverse and abundant genera of ectomycorrhizal fungi with at least 240 species from the Andean mountains. Secotioid and gasteroid forms were until recently considered primarily within Thaxterogaster, resulting in a confusing intrageneric classification system. Moser and Horak suggested that Thaxterogaster was nested within Cortinarius. The modern molecular analysis of Peintner et al. investigated the multiple origins of sequestrate taxa related to Cortinarius and consequently synonymized Thaxterogaster to Cortinarius. Subsequent molecular phylogenies have resolved the polyphyletic nature of Thaxterogaster and other "cortinarioid" taxa within Cortinarius but have also highlighted the fact that most sequestrate Patagonian taxa lack molecular data. Original descriptions of these fungi are available mostly in German and Spanish and the interpretations of morphological structures are outdated considering the current state of knowledge about sporemorphology and ontogeny. For example, verrucae on spores were illustrated as globose structures whereas SEM shows that they are complex conical structures that are sometimes interconnected by reticula or sub-reticula. External walls or episporia were sometimes pictured in original descriptions but our analyses suggest that these may have been optical illusions due to non-DIC microscopy. Recently, the incorrect interpretation of this episporium in the "cortinariod" fungi was found to be a misleading character. Despite recent advances in Cortinarius systematics, the current classification, diversity andecology of secotioid and hypogeous "cortinarioid" fungi in the Nothofagaceae forests of southern South America remains unclear. The objective of this study is to update descriptions with diagnostic characters, including color photos of basidiomata, SEM images of spores, and ITS sequence data to clarify the biodiversity of these fungi in Patagonia. Original descriptions of secotioid and gasteroid taxa were also revised and translated to English. Our analyses based on SEM and ITS rDNA resolves at least 15 species with names that need to be considered as synonyms. The use of these tools combined with an extensive database of described species also facilitated the recognition of several new and undescribed Patagonian species. Analysis of spore ultrastructure across many specimens clearly shows that sequestrate species of Cortinarius always lack a perisporium. It also indicates that there is a transition process in shape and ornamentation that occurs in taxa as they switch from ballistosporic tostatimosporic spore dispersal.