Arthrocatenales, a new order of extremophilic fungi in the Dothideomycetes

Abstract

The widely treated order Capnodiales is one of the most important orders in the class Dothideomycetes. Recently, the order Capnodiales s. lat. was reassessed and split into seven orders (Capnodiales s. str., Cladosporiales, Comminutisporales, Mycosphaerellales, Neophaeothecales, Phaeothecales and Racodiales) based on multi-locus phylogeny, morphology and life strategies. In this study, two Arthrocatena strains isolated from sooty mould communities on the leaves of Tiliacordata and needles of Pinusnigra in southern Poland were analyzed. Multi-locus phylogenetic analyses (ITS-LSU-SSU-rpb2-tef1) along with morphological examination showed that they belong to Capnobotryellaantalyensis, which represents a sister taxon to Arthrocatenatenebrosa. Capnobotryellaantalyensis is a rock-inhabiting fungus described from Turkey. The following new combination is proposed: Arthrocatenaantalyensis. Phylogenetic analyses also showed that Arthrocatena and related genus Hyphoconis, both known previously only from rocks, form a sister lineage to orders Cladosporiales and Comminutisporales. The new order Arthrocatenales and new family Arthrocatenaceae are proposed to this clade. Representatives of this order are extremophilic fungi that live on rocks and in sooty mould communities.

Keywords: Dothideomycetes; molecular phylogeny; new combination; new family; new order; taxonomy.

Figure 1.

Reduced phylogenetic tree of selected members of the Capnodiales s. lat., Dothideales and Myriangiales, including all described species of the genera Arthrocatena and Hyphoconis, obtained from a maximum likelihood analysis of the combined multi-locus alignment (ITS, LSU, SSU, rpb2, tef1). The positions of new strains, Arthrocatenaantalyensis comb. nov. and new order Arthrocatenales are indicated in bold. Ex-type cultures are indicated with superscript T. Numbers above branches indicate maximum likelihood bootstrap (MLB) support values > 60% and Bayesian posterior probabilities (BPP) > 0.95, respectively (MLB/BPP). Schismatommadecolorans was used as an outgroup. The scale bar represents the expected number of changes per site.

Figure 2.

Morphology of Arthrocatenaantalyensis (strain CBS 150720, e–h slide culture on PDA): a, b general view and detailed view of upper side of colony on MEA after 4 weeks of growth at 25 °C c, d general view and detailed view of upper side of colony on PDA after 4 weeks of growth at 25 °C e general view of hyphae f, g straight hyphae (note anastomosing hyphae visible on figure g) h terminal, flexuose and torulose hyphae. Scale bars: 50 µm (e); 10 µm (f–h).

Figure 3.

Morphology of Arthrocatenaantalyensis (strain CBS 150720, slide culture on PDA): a general view of hyphae, arthroconidia and chlamydospore b–d arthroconidia e chlamydospore-like cells f–g chlamydospore-like cells and muriformly septate chlamydospores (indicated by arrows). Scale bars: 50 µm (a); 10 µm (b–g).

Figure 4.

Morphology of Arthrocatenaantalyensis (strain CBS 150720, on MEA): a, b arthroconidia, arrows indicate disintegrating chains of arthroconidia c–e disintegrated arthroconidia. Scale bars: 10 µm (a–e).