Placement of Triblidiaceae in Rhytismatales and comments on unique ascospore morphologies in Leotiomycetes (Fungi, Ascomycota)

Ramomarthamyces octomerus sp. nov. and Insights into the Evolution and Diversification of Ramomarthamyces (Ascomycota, Leotiomycetes, Marthamycetales)

The apothecial fungus Ramomarthamyces octomerus sp. nov. is described from specimens collected in Mediterranean climate regions in southern Portugal, Spain (Canary Islands), and the Dalmatian region of Croatia. Presumably saprobic, R. octomerus occurs on intact, decorticated wood of Laurus novocanariensis and Olea europaea. Ascospores are cylindric-ellipsoid and seven-septate. Surprisingly, in our four-locus phylogenetic analysis (nuSSU, ITS1-5.8S-ITS2, LSU, mtSSU), this fungus clusters among species of Cyclaneusma, Marthamyces, Naemacyclus, and Ramomarthamyces in a core Marthamycetaceae clade that circumscribes primarily leaf-inhabiting, filiform-spored species. In addition, the asci of R. octomerus possess an amyloid pore, but the reaction varies between specimens collected in the Canary Islands and those collected in Portugal and Croatia. The occurrence of an amyloid reaction in the asci of R. octomerus challenges the characterization of Marthamycetales taxa as possessing inamyloid asci. In our discussion we provide background and analysis of these notable observations.

Apothecial Ancestry, Evolution, and Re-Evolution in Thelebolales (Leotiomycetes, Fungi)

Simple Summary

Leotiomycetes is one of the most speciose classes of the phylum Ascomycota (Fungi). Its species are mainly apothecioid, paraphysate, and possess active ascospore discharge. Thelebolales are a distinctive order of the Leotiomycetes class whose members have mostly closed ascomata, evanescent asci, and thus passively dispersed ascospores. Within the order, a great diversity of peridia have evolved as adaptations to different dispersal strategies. The genus Thelebolus is an exceptional case of ascomatal evolution within the order. Its species are the most diverse in functional traits, encompassing species with closed ascomata and evanescent asci, and species with open ascomata, active ascospore discharge, and paraphyses. Open ascomata were previously suggested as the ancestral state in the genus, these ascomata depend on mammals and birds as dispersal agents. In our work, we used morphological and phylogenetic methods, as well as the reconstruction of ancestral traits for ascomatal type, asci dehiscence, the presence or absence of paraphyses, and ascospore features to explore evolution within Thelebolales. We demonstrate the apothecial ancestry in Thelebolales and propose a new hypothesis about the evolution of the open ascomata in Thelebolus involving a process of re-evolution where the active dispersal of ascospores appears independently twice within the order. A new family, Holwayaceae, is proposed within Thelebolales, comprising three genera: Holwaya, Patinella, and Ramgea.

Abstract

Closed cleistothecia-like ascomata have repeatedly evolved in non-related perithecioid and apothecioid lineages of lichenized and non-lichenized Ascomycota. The evolution of a closed, darkly pigmented ascoma that protects asci and ascospores is conceived as either an adaptation to harsh environmental conditions or a specialized dispersal strategy. Species with closed ascomata have mostly lost sterile hymenial elements (paraphyses) and the capacity to actively discharge ascospores. The class Leotiomycetes, one of the most speciose classes of Ascomycota, is mainly apothecioid, paraphysate, and possesses active ascospore discharge. Lineages with closed ascomata, and their morphological variants, have evolved independently in several families, such as Erysiphaceae, Myxotrichaceae, Rutstroemiaceae, etc. Thelebolales is a distinctive order in the Leotiomycetes class. It has two widespread families (Thelebolaceae, Pseudeurotiaceae) with mostly closed ascomata, evanescent asci, and thus passively dispersed ascospores. Within the order, closed ascomata dominate and a great diversity of peridia have evolved as adaptations to different dispersal strategies. The type genus, Thelebolus, is an exceptional case of ascomatal evolution within the order. Its species are the most diverse in functional traits, encompassing species with closed ascomata and evanescent asci, and species with open ascomata, active ascospore discharge, and paraphyses. Open ascomata were previously suggested as the ancestral state in the genus, these ascomata depend on mammals and birds as dispersal agents. In this scheme, species with closed ascomata, a lack of paraphyses, and passive ascospore discharge exhibit derived traits that evolved in adaptation to cold ecosystems. Here, we used morphological and phylogenetic methods, as well as the reconstruction of ancestral traits for ascomatal type, asci dehiscence, the presence or absence of paraphyses, and ascospore features to explore evolution within Thelebolales. We demonstrate the apothecial ancestry in Thelebolales and propose a new hypothesis about the evolution of the open ascomata in Thelebolus, involving a process of re-evolution where the active dispersal of ascospores appears independently twice within the order. We propose a new family, Holwayaceae, within Thelebolales, that retains the phenotypic features exhibited by species of Thelebolus, i.e., pigmented capitate paraphyses and active asci discharge with an opening limitation ring.

Phylogenetic placement and lectotypification of Pseudotryblidium neesii (Helotiales, Leotiomycetes)

A phylogenetic analysis of combined rDNA LSU and ITS sequence data was carried out to determine the phylogenetic placement of specimens identified as Pseudotryblidium neesii. The species forms a distinct clade within Dermateaceae (Helotiales, Leotiomycetes) with Rhizodermea veluwiensis and two Dermea species. The geographical distribution of this species, previously known only from Europe on Abies alba, is extended to north-western North America where it grows exclusively on A. grandis. The name P. neesii is lectotypified in order to disentangle the complicated nomenclature of the species. A new, detailed description of P. neesii with illustrations is provided after comparison of sequenced specimens with the type material. Furthermore, the new combination Pseudographis rufonigra (basionym Peziza rufonigra) is made for a fungus previously known as Pseudographis pinicola.

Three new species and a new combination of Triblidium

Triblidiaceae (Rhytismatales) currently consists of two genera: Triblidium and Huangshania. Triblidium is the type genus and is characterised by melanized apothecia that occur scattered or in small clusters on the substratum, cleistohymenial (opening in the mesohymenial phase), inamyloid thin-walled asci and hyaline muriform ascospores. Before this study, only the type species, Triblidium caliciiforme, had DNA sequences in the NCBI GenBank. In this study, six specimens of Triblidium were collected from China and France and new ITS, mtSSU, LSU and RPB2 sequences were generated. Our molecular phylogenetic analysis and morphological study demonstrated three new species of Triblidium, which are formally described here: T. hubeiense, T. rostriforme and T. yunnanense. Additionally, our results indicated that Huangshania that was considered to be distinct from Triblidium because of its elongated, transversely-septate ascospores, is congeneric with Triblidium. Therefore, we have placed Huangshania in synonymy under Triblidium, rendering Triblidiaceae a monotypic family.