Hypoxylon Bull.

Rathnayaka, Achala R., Chethana, K. W. Thilini, Manowong, Areerat, Bhagya, Amuhenage T., Win, Hsan, Tun, Zaw L., Mapook, Ausana & Hyde, Kevin D., 2025, Taxonomy, phylogeny, and bioactive potential of Xylariales (Sordariomycetes, Ascomycota) from Thailand: novel species discovery, new host and geographical records, and antibacterial properties, MycoKeys 120, pp. 35-117 : 35-117

Hypoxylon Bull. , Hist. Champ. Fr. (Paris) 1: 168 (1791)

Notes.

Bulliard (1791) introduced Hypoxylon to accommodate H. fragiforme (basionym: H. coccineum ) as the type species. The sexual morph of this genus is characterized by ascomata embedded in a colorful, effused, or pulvinate stroma containing secondary metabolites ( Ju and Rogers 1996). The ascomata are perithecioid, monostichous, and open separately through umbilicate, rarely slightly papillate ostioles. The asci are 8 - spored, unitunicate, cylindrical, stipitate, and provided with a typically amyloid apical apparatus. The ascospores are unicellular, ellipsoid, and brown and have a germ slit on the most convex side of the inequilateral ascospores ( Ju and Rogers 1996). The asexual morph is characterized by a nodulisporium-like morph, but other types of conidial states have also been observed, such as sporothrix-like, virgariella-like, and periconiella-like ( Ju and Rogers 1996). The evolutionary relationships of hypoxylaceous fungi have been studied using phylogenetic, chemotaxonomic, and morphological data ( Kuhnert et al. 2021). Most of the Hypoxylon species have been able to produce highly bioactive secondary metabolites, which are released from the stromata ( Ju and Rogers 1996; Kuhnert et al. 2014 b; Fournier et al. 2016). Hypoxylon species have a cosmopolitan distribution and are recorded as saprotrophs that grow on dead wood, endophytes in seed plants, and facultative parasites on diseased hosts ( Ju and Rogers 1996; Stadler 2011; Kuhnert et al. 2014 a; Daranagama et al. 2018; Helaly et al. 2018; Rogers 2018). Hyde et al. (2024) listed 200 species under this genus, while 466 are included in the Index Fungorum (2025).

Phylogenetic analyses for Hypoxylaceae

For Hypoxylon , 150 taxa were included in the combined data set (ITS, LSU, rpb 2, and β-tub). Graphostroma platystomum ( CBS 270.87 ), Natonodosa speciosa ( CLM RV 86 ), Xylaria arbuscula ( CBS 126415 ), and X. hypoxylon ( CBS 122620 ) were used as the outgroup taxa. After alignment, the dataset comprised 3003 characters, including gaps (ITS = 614 bp, LSU = 822 bp, rpb 2 = 1017 bp, β-tub = 550 bp). Both the ML and BI analyses exhibit a similar tree topology. The best-scoring RAxML tree was obtained (Fig. 13 ), with a final likelihood value of - 75469.623433. The matrix included 1852 distinct alignment patterns, with 29.09 % undetermined characters or gaps. The estimated base frequencies were as follows: A = 0.247189, C = 0.251478, G = 0.262907, and T = 0.238426; substitution rates were AC = 1.284950, AG = 4.479967, AT = 1.344479, CG = 1.074839, CT = 6.471802, and GT = 1.0; and the gamma distribution shape parameter α = 0.313445. In the BI analysis, the average standard deviation of the split frequencies was 0.01 after 5,000,000 generations of runs. The phylogenetic tree topology is similar to the study by Karimi et al. (2023). According to the phylogenetic analyses, our strains ( MFLU 24-0530 , MFLUCC 25-0024 , MFLUCC 24-0613 , MFLU 24-0532 , and MFLUCC 24-0612 ) cluster within Hypoxylon and Hypomontagnella .

Figures

Figure 13. Phylogram generated from ML analysis based on the combined dataset of ITS, LSU, rpb 2, and β-tub. The tree is rooted to Graphostroma platystomum (CBS 270.87), Natonodosa speciosa (CLM RV 86), Xylaria arbuscula (CBS 126415), and X. hypoxylon (CBS 122620). Bootstrap support values for ML ≥ 70 % and Bayesian posterior probabilities (PP) ≥ 0.90 are noted at the nodes. Strain numbers are noted after the species names. Strains isolated in this study are represented in blue, and type strains are in bold.