MYCOBANK. — MB 82430.

FACESOFFUNGI NUMBER. — FoF 03949.

ETYMOLOGY. — Referring to the common name of the host ecosystem.

C ULTURE CHARACTERISTICS. — Colonies on PDA reaching 5 cm diam., after two weeks at 20-25°C, medium dense, irregular, flat, surface smooth with undulate edge, colony from above yellow at the margin, greenish yellow at the centre; from below yellowish white at the margin, greenish yellow at the centre; mycelium greenish yellow, not produced pigmentation.

MATERIAL EXAMINED. — Thailand, Ranong Province, Amphoe Muang, Mu 4 Tambol Ngao, Ranong Mangrove Research Center (9°43’- 9°57’N, 98°29’- 98°39’E), on fallen decaying twig of Bruguiera cylindrica, 6.XII.2016, Monika C. Dayarathne, MCD 067 (holo-, MFLU 17-0412), ex-type living culture, MFLUCC 17-0412, ICMP 21769; on fallen decaying twig of B. cylindrica, 6.XII.2016, Monika C. Dayarathne, MCD 030 (iso-, MFLU 18-0147), ex-type living culture, MFLUCC 17-0391; on fallen decaying twig of B. cylindrica, 6.XII.2016, Monika C. Dayarathne, MCD 034 (MFLU 18-0148), ex-type living culture, MFLUCC 17-0394.

DISTRIBUTION. — Thailand

Saprobic on submerged decaying wood of Bruguiera cylindrica.

Ascostromata. 1-2 × 0.8-1 cm, scattered or aggregated on host, erumpent, arising through cracks on the bark, edges of ascostromata remaining as pointed, angular parts, carbonaceous, with numerous perithecia immersed in one stroma.

Ostiole. Opening through host bark and appearing as black spots, composed of an outer layer of dark brown, small, tightly packed, thin parenchymatous cells and an inner layer of yellowish white, large, loosely packed, parenchymatous cells.

Ascomata. 480-500 × 300-340 µm (ẍ = 490 × 320 µm, n = 0), perithecia immersed in stromatic tissue, aggregated, brown, globose to sub-globose, narrowing towards the apex and very narrow at the base of ostiolar canal, thin-walled, ostiolate; ostiolar canal, periphysate, ostiolar opening covered with carbonaceous, black cells; periphyses hyaline, filamentous.

Peridium. 40-45 µm wide, comprising an outer layer of yellow-brown, thick-walled cells of textura angularis and a thin, inner stratum of yellow, thick-walled cells of textura angularis.

Asci. 90-120 × 6-8 µm (ẍ = 105 × 7 µm, n = 30), unitunicate, 8-spored, with long, narrow, thin-walled stalk, with cylindrical, thick-walled, swollen upper portion, apex flat, with J-, cylindrical, conspicuous apical ring.

Ascospores. 5-10.5 × 1.5-2.5 µm (ẍ = 7.5 × 2 µm, n =30), seriate, hyaline becoming yellowish at maturity, allantoid, unicellular, thin-walled, with small fat globules at each end, smooth-walled.

Undetermined.

Diatrype mangrovei Dayarathne & K.D.Hyde, sp. nov., was recorded from intertidal attached wood of Bruguiera cylindrica from Ranong, Thailand. In the phylogenetic analyses of both ITS and concatenated ITS+Btub data (Figs 1; 2) it grouped in a clade with Diatrype and Diatrypella species. Diatrype mangrovei Dayarathne & K.D.Hyde, sp. nov., shares similar morphological features with the genus Diatrype and is distinguished from Diatrypella species by being octosporous. Diatrype enteroxantha (HUEFS155114, HUEFS155116) showed close phylogenetic affinity to this new species (subclade A 4 in clade A, Fig. 1) but D. enteroxantha has smaller asci (18-28.5 × 5-9 µm vs 90-120 × 6-8 µm) (de Almeida et al. 2016). There are 14 bp differences out of 520 bp (2.69%) between D. enteroxantha and D. mangrovei Dayarathne & K.D.Hyde, sp. nov., According to ITS phylogeny, D. mangrovei Dayarathne & K.D.Hyde, sp. nov., formed an intermediate clade (sub-clade L 4 in clade L) to D. enteroxantha and D. oregonensis (DPL200) (Fig. 2). Diatrype mangrovei Dayarathne & K.D.Hyde, sp. nov., is easily distinguishable from D. oregonensis by having globose to sub-globose ascomata while the latter species has ovoid or ellipsoid ascomata with a white entostroma that becomes yellow to brown (Trouillas et al. 2010a). However, there are 16 bp are differences out of 526 bp (3.04%) in ITS region between D. oregonensis and D. mangrovei Dayarathne & K.D.Hyde, sp. nov., Morphological differences of D. mangrovei Dayarathne & K.D.Hyde, sp. nov., and related taxa are summarized in the Table 5. This is the first record of Diatrype species from a mangrove habitat.