Taxonomy and Phylogeny of Corticioid Fungi in Auriculariaceae (Auriculariales, Basidiomycota): A New Genus, Five New Species and Four New Combinations

The Auriculariaceae accounts for most of the species in the Auriculariales, and all species in the family are wood-decaying fungi with gelatinous, crustaceous, or woody basidiomes. Many new taxa were published recently, but the taxonomy and phylogeny of the corticioid species in the Auriculariaceae are far from resolved. We undertook a comprehensive taxonomic and phylogenetic study of the family with emphasis on corticioid specimens collected from East and Southeast Asia. Phylogenetic analyses on concatenated ITS and 28S rDNA sequences of representative taxa of the Auriculariaceae and the genera Eichleriella and Heteroradulum were carried out that resolved five new lineages. Heterocorticium gen. nov. is established for two species with resupinate coriaceous basidiomes with smooth, pigmented hymenophores. Five new species, H. bambusicola (generic type), H. latisporum, Eichleriella alpina, E. bambusicola, and Heteroradulum maolanense, are described and illustrated. In addition, Heterochaete delicata, H. discolor, and H. sinensis are transferred to Eichleriella, whereas H. roseola is regarded as a synonym of Kneiffia discolor (= H. discolor). Eichleriella aculeobasidiata is treated as a synonym of Heterochaete sinensis (= E. sinensis). Heterochaete mussooriensis is transferred to Heteroradulum with Heteroradulum semis as a heterotypic synonym. The present study contributes to the understanding of species diversity, taxonomy, and phylogeny of corticioid fungi in Asia.


Introduction
Auriculariaceae is the largest and best-supported clade in the Auriculariales (Basidiomycota) and consists of a large group of wood-decaying fungi with varied basidiome configurations [1][2][3][4] (Figure 1). Within the family are the well-known jelly fungi in Auricularia Bull. and Exidia Fr. that have been intensively studied by several authors in recent years, although the latter genus remains polyphyletic [5][6][7][8][9][10][11]. Species with poroid hymenophores in Aporpium Bondartsev & Singer, Elmerina Bres., and Protodaedalea Imazeki are also members of the Auriculariaceae [12][13][14]. Corticioid and stereoid taxa are numerous in Auriculariaceae and typically classified in three main genera, Eichleriella Bres., Exidiopsis (Bref.) A. Møller, and Heterochaete Pat. [15][16][17][18][19]. The genera were distinguished primarily by the morphology of the basidiome and hymenophore. Our understanding of these genera has changed dramatically since the phylogenic study of Malysheva and Spirin [15]. They showed that the generic types of Heterochaete and Exidiopsis, H. andina Pat. & Lagerh. and E. effusa (Bref. ex Sacc.) A. Møller, respectively, were placed together in a well-supported lineage, and other species of Heterochaete were nested within the Eichleriella s.s. and Heteroradulum Lloyd ex Spirin & Malysheva clades. They reintroduced Heteroradulum to accommodate Eichleriella kmetii Bres. and related species that are distantly related Microscopically, taxa in the Auriculariaceae and in the Auriculariales share many common morphological characters [3]. Except for Auricularia that has transversely septate basidia, all other species have typical tremellaceous basidia that are longitudinally septate. Dikaryophyses are usually present in enclosing the basidia, and basidiospores are mostly cylindrical to broadly ellipsoid and relatively large.
Many new genera and species have been described recently; nevertheless, the species diversity of the corticioid fungi in the Auriculariaceae in subtropical and tropical Asia has not been sufficiently explored. The taxonomy and phylogenetic relationships of previously described taxa from the region need to be studied and integrated with the newer taxa. In the present study, we performed (1) phylogenetic analyses of Auriculariaceae by adding corticioid taxa recently collected from East and Southeast Asia and (2) morphological examinations of recent collections as well as type specimens of some older species. We resolved five new lineages, including a new genus named Heterocorticium. Five new species in Heterocorticium, Eichleriella, and Heteroradulum were described and illustrated. Microscopically, taxa in the Auriculariaceae and in the Auriculariales share many common morphological characters [3]. Except for Auricularia that has transversely septate basidia, all other species have typical tremellaceous basidia that are longitudinally septate. Dikaryophyses are usually present in enclosing the basidia, and basidiospores are mostly cylindrical to broadly ellipsoid and relatively large.
Many new genera and species have been described recently; nevertheless, the species diversity of the corticioid fungi in the Auriculariaceae in subtropical and tropical Asia has not been sufficiently explored. The taxonomy and phylogenetic relationships of previously described taxa from the region need to be studied and integrated with the newer taxa. In the present study, we performed (1) phylogenetic analyses of Auriculariaceae by adding corticioid taxa recently collected from East and Southeast Asia and (2) morphological examinations of recent collections as well as type specimens of some older species. We resolved five new lineages, including a new genus named Heterocorticium. Five new species in Heterocorticium, Eichleriella, and Heteroradulum were described and illustrated. In addition, the taxonomic and phylogenetic positions of some species of Heterochaete and Eichleriella were determined, resulting in the proposal of several new combinations.

Materials and Methods
Specimen collection, morphological studies, DNA extraction and sequencing and phylogenetic analyses followed [24]. Three separate datasets of concatenated ITS-28S sequences of the Auriculariaceae, Eichleriella and Heteroradulum were analyzed (Table 1)

Phylogenetic Analyses
The Auriculariaceae dataset contained 58 ITS and 57 28S sequences from 61 samples representing 47 ingroup taxa and the outgroup (Table 1) jModelTest suggested SYM+I+G as the best-fit models of nucleotide evolution for the Auriculariaceae dataset, and GTR+I+G for the Eichleriella and Heteroradulum datasets. The average standard deviations of split frequencies of BI were 0.008874, 0.007964, and 0.003569 for the three datasets at the end of the runs. The MP, ML, and BI analyses of the three datasets resulted in almost identical tree topologies. The MP tree of the Auriculariaceae is shown in  jModelTest suggested SYM+I+G as the best-fit models of nucleotide evolution for the Auriculariaceae dataset, and GTR+I+G for the Eichleriella and Heteroradulum datasets. The average standard deviations of split frequencies of BI were 0.008874, 0.007964, and 0.003569 for the three datasets at the end of the runs. The MP, ML, and BI analyses of the three datasets resulted in almost identical tree topologies. The MP tree of the Auriculariaceae is shown in Figure 2, whilst ML trees of Eichleriella and Heteroradulum are shown in    In the Auriculariaceae tree ( Figure 2), 19 distinct lineages corresponding to 18 known genera and the new genus, Heterocorticium, were recognized. Two new species of Heterocorticium, H. bambusicola and H. latisporum, formed a distinct lineage with strong support values (93/94/1). The lineages representing Eichleriella and Heteroradulum were strongly supported as monophyletic genera. In the Eichleriella tree ( Figure 3), seventeen distinct lineages including two new species, E. alpina and E. bambusicola, and clades representing three Heterochaete species, H. delicata, H. discolor, H. sinensis, were recognized. Two samples of E. aculeobasidiata, including the holotype (CLZhao 6159) and one sample identified as Heterochaete delicata (TUFC33717), were nested within the E. sinensis lineage (61/73/1). In the Heteroradulum tree ( Figure 4)
Notes-Eichleriella alpina is characterized by having discoid-to-slightly effused-reflexed basidiomes, a distinct basal layer, relatively large basidiospores and a distribution in temperate areas of southwestern China. Eichleriella macrospora (Ellis and Everh.) G.W. Martin is similar but differs in having slightly shorter basidiospores (10-15 × 5-7 μm) and a distribution in the north central USA [33]. In the phylogenetic tree, E. alpina formed a distinct lineage in the Eichlerilla clade ( Figure 3). Etymology-refers to growing on bamboo.
Distribution-Australia, Cambodia, China, Nepal, New Zealand, Philippines, Sri Lanka, Thailand, Vietnam. Type specimens examined-Australia, New South Wales, Moruya, on bare wood, W.N. Cheesman, 1914 (K(M) Representative specimens examined-Australia, Victoria, Gippsland Highland, Tarra Valley, on fallen branches of orangewood, 12 Sept 1955, K. Healy, N.W.M. Walters, & E. DaCosta (MEL-2313649, as H. discolor); Cambodia, Reserv foretrie de Campong Chhnang, on (bark of) dead branches, July 1921, P.A. Pételot 360 (FH-HUH00940161; BPI-719711, as H. roseola); China, Gansu Province, Tianshui County, Maijishan Forest Park, on fallen basidiomes, small hyphal pegs arising from subiculum and composed of brownish yellow, sclerified hyphae and dikaryophyses, and 4-sterigmate basidia. The margin of specimens can be quite variable, and hyphal pegs are brittle, often breaking off to expose its dark brown interior. The size of the basidiospores is also variable and may reflect the number of sterigmata produced by the basidia. Its hyphal system was described as pseudodimitic [36], because the hyphae in the subiculum and hyphal peg are brownish yellow with slightly thickened walls. On close inspection, however, rare clamp connections were observed on these sclerified hyphae.
In the phylogenetic tree of Eichleriella (Figure 3), E. sinensis, E. tenuicula and E. delicata are closely related but formed distinct lineages. The recently described species, E. aculeobasidiata Hui Wang, Dong Qiong Wang & C.L. Zhao, has 2-sterigmate basidia but nested within the E. sinensis lineage [28]. Close inspection of basidia of the type specimens of E. aculeobasidiata needs to be carried out, but at present we accept E. aculeobasidiata as a synonym of E. sinensis based on phylogenetic analyses and overall morphology. A sample from Japan identified as Heterochaete delicata (TUFC33717) in GenBank also nested within the E. sinensis lineage instead of the E. delicata lineage in our phylogenetic tree ( Figure 3). Etymology-refers to the type locality in Maolan Nature Reserve, Guizhou Province, southwestern China.