Lactocollybia polyhabitata I. Bera, 2025

Bera, Ishika, Wisitrassameewong, Komsit & Thongklang, Naritsada, 2025, New insights into Lactocollybia (Agaricales, Basidiomycota): Morpho-phylogenetic analyses revealing two interesting species and one new record from Thailand and evidence of intercontinental conspecificity, MycoKeys 118, pp. 313-344 : 313-344

Lactocollybia polyhabitata I. Bera sp. nov.

Figs 5 , 6

Diagnosis.

The ellipsoid to oblong, uni- to multi-guttulate basidiospores and absence of hymenial gloeocystidia distinguish this Lactocollybia species.

Type.

Thailand • Narathiwat Province: Princess Sirindhorn Wildlife Sanctuary , N 6°4.4388'N, 101°58.14594'E, Alt. 30 m, gregarious on a dead log submerged in the water in a peat swamp forest, 4 th August 2023, I. Bera, IB 23 - N 15 ( MFLU 24-0390 , holotype!)

Etymology.

The epithet ‘ polyhabitata ’ refers to the occurrence of the species across diverse habitat types, ranging from peat swamp forests to tropical forests.

Description.

Basidiomata small-sized, collybioid. Pileus 6–16 mm diam., planoconvex when young, gradually becoming applanate on maturity; surface dry, minutely pruinose, hygrophanous; yellowish white (1 A 2), sometimes with greyish yellow (4 B 3) patches near the center; margin entire to undulate, decurved. Lamellae adnate, yellowish white (1 A 2), crowded (37 L + l / cm at pileus margin); lamellulae present in 4–5 series; edge entire to eroded. Stipe 10.4–15.7 × 1.3–2.2 mm, eccentric, cylindrical but tapering towards base; surface dry, smooth, hygrophanous; yellowish white (1 A 2) at apex gradually becoming pale yellow to light yellow (4 A 3–5) at base; basal mycelium white. Context in pileus up to 1.8 mm thick, white (1 A 1), unchanged on bruising, exposure, and in 3 % KOH; hollow in stipe, yellowish white (1 A 2), unchanging on bruising, exposure, and in 3 % KOH.

Basidiospores 6.3–8.2 – 10.6 × 3.4–4.1 – 4.9 μm [n = 30, Q = 1.48–2.01 – 2.62], ellipsoid to oblong; thin-walled, smooth, apiculate, uni- to multi-guttulate, hyaline in 5 % KOH, inamyloid, non-dextrinoid. Basidia 22.1–29.2 × 4.6–6.6 μm, subclavate, thin-walled, hyaline in 5 % KOH, non-dextrinoid, 4 - spored; sterigmata up to 3.8 μm long. Basidioles 14.5–27.5 × 4.6–5.8 μm, subclavate, thin-walled, hyaline in 5 % KOH, non-dextrinoid; sometimes have crystalline content. Lamellae edge fertile, heteromorphous with basidia, basidioles, and cystidia. Pleurocystidia absent. Hymenial gloeocystidia absent. Cheilocystidia abundant, 15.6–36.6 × 2.5–6.2 μm, variable in shape from subcylindrical, subclavate to lageniform with obtuse to sub-capitate apices, sometimes with swollen bases abruptly tapering towards apices forming undulating long necks, thin-walled, hyaline in 5 % KOH; content rare, crystalline; emergent up to 20 μm. Subhymenium thin, up to 10 μm thick, subcellular with ramifying hyphae. Hymenophoral trama composed of compactly arranged, subparallel to parallel, thin-walled, septate hyphae; hyphae up to 3.5 μm wide. Pileipellis a cutis; composed of loosely interwoven, septate hyphae with numerous scattered long, fusoid gloeohyphal elements; hyphae 1.7–3.2 μm wide, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; gloeohyphal elements 22–95 × 8–19.2 μm, attenuated at both ends, refractive, yellowish in H 2 O and 5 % KOH. Pileus trama composed of compactly arranged, interwoven hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Stipitipellis a cutis; composed of loosely interwoven, uprising hyphae with numerous scattered gloeocystidia and caulocystidia; hyphae 1.5–2.3 μm wide, thin-walled, septate, hyaline in 5 % KOH, non-dextrinoid; gloeocystidia lageniform, 13.5–45.7 × 4–9.2 μm, attenuated at both ends, refractive, yellowish in H 2 O and 5 % KOH; caulocystidia 19.2–21.6 × 3.2–6 μm, similar to cheilocystidia but shorter. Stipe trama similar to pileus trama, composed of compactly arranged, parallel hyphae and gloeohyphal elements; hyphae hyaline in 5 % KOH, non-dextrinoid. Clamp connections common.

Additional material examined.

Thailand • Phrae Province: roadside , 18°10.75188'N, 100°10.82418'E, Alt. 171 m, gregarious on a dead tree log in semi-deciduous Dipterocarpus dominated forest, 3 rd August 2024, I. Bera, IB 24-47 ( MFLU 24-0391 , paratype) .

Notes.

Lactocollybia polyhabitata belongs to the sect. Albae due to its subcellular structure with ramifying hyphae in the subhymenium, presence of gloeohyphal elements, and clamp connections ( Singer 1986). The species can be confused with other species by typical field characters such as small-sized and yellowish-white basidiomata, hygrophanous and pruinose surfaces, and crowded lamellae. However, it can be distinguished by microscopic characters such as the presence of small cheilocystidia (with crystalline content) and caulocystidia and the absence of pleurocystidia and hymenial gloeocystidia. The species is found in various habitats at low elevations (30–171 m above sea level), including peat swamp forests and Dipterocarpus dominated forests.

Nearly all Lactocollybia species possess prominent hymenial gloeocystidia, readily distinguishing L. polyhabitata ( Singer and Digilio 1952; Pegler 1977, 1986; Singer 1989; Reid and Eicker 1998). However, this character makes it similar to a few species, the African L. gracillima ( Pegler 1977) and Chinese L. subvariicystis ( Hosen et al. 2016) . Lactocollybia gracillima differs by its transparent striations almost reaching the pileus center, decurrent lamellae, smaller basidiospores (5.3–7.3 × 2.7–3.7 μm), clavate-cylindric cheilocystidia with subcapitate to rounded apices, and caulocystidia with refractive contents ( Pegler 1977). Lactocollybia subvariicystis is differentiated by adnexed to sinuate lamellae attachment, amygdaliform to fusoid, pale yellowish basidiospores, the presence of pleurocystidia, and fusoid to subfusoid or lageniform with long-necked cheilocystidia, easily separating from L. polyhabitata .

The oblong basidiospore of L. polyhabitata also makes it unique. This character easily distinguishes it from other species with white basidiomata, such as L. subvariicystis (amygdaliform to broadly fusoid), L. globosa (ovoid to subglobose to tear-shaped), L. piliicystis (amygdaliform), L. variicystis (broadly amygdaliform), L. microspora (ellipsoid), and L. gracillima (ellipsoid to lacrymoid) ( Singer 1962; Pegler 1977; Reid and Eicker 1998; Hosen et al. 2016). Though a similarly shaped basidiospore is reported in L. epia (as elongate-ellipsoid or fusoid), the presence of hymenial gloeocystidia and fine granular surface incrustations of pileus hyphae separates this species from L. polyhabitata ( Pegler 1977, 1986).

Phylogenetically, nrITS sequences of our samples (PQ 530288 – PQ 530289) clustered with three sequences designated as L. angiospermarum and three unidentified sequences (KP 012742, OR 785928, and MH 166807 ) with strong support (MLB 100 and BPP 1, Fig. 1 ). Lactocollybia angiospermarum was originally found in the USA by Singer (1948) and subsequently reported in East Africa by Pegler (1977). The species has been considered as a synonym of L. epia by various authors ( Pegler 1986; Reid and Eicker 1998; Yang 2000). According to the protologue of L. angiospermarum and L. epia and the description of L. angiospermarum written by Pegler (1977), the morphology of both species is similar (Table 4 ). We could not assess the conspecificity of both species molecularly in this study. The public sequences designated for both species in this study lack morphological data. The sequences of L. angiospermarum ( MH 166807 , PP 850289, and PP 850674) did not cluster with public L. epia sequences [labeled as L. cf. epia 1 and L. cf. epia 2 clades in this study (Fig. 1 )]. At this stage, based on the available morphological data of both species, we agree that L. angiospermarum could be considered as the synonym of L. epia . The additional samples from the type locality coupled with morphological data would be helpful in taxonomic reassessment of both species.

Lactocollybia polyhabitata differs from both L. epia and L. angiospermarum by having ellipsoid to oblong basidiospores (Q = 1.48–2.62), the absence of gloeocystidia in the hymenium, and yellowish gloeohyphal content (Table 4 ). Thus, this species is quite different based on the morphological distinction.

Figures

Figure 1. Phylogram inferred from maximum likelihood (ML) analysis by raxmlGUI 2.0 and Bayesian inference by Mr. Bayes v. 3.2. 6 based on nrITS sequence data. Generated sequences in this study are presented in red bold for the novel species and blue bold for the new record. Sequences of L. cf. epia are presented in green bold. The clade representing L. variicystis, L. polyhabitata sp. nov., and L. cf. epia are demarcated by the yellow, blue, and purple boxes, respectively. Maximum likelihood bootstrap support values (MLB) ≥ 70 % are shown on the left of “ /, ” and Bayesian posterior probabilities (BPP) ≥ 0.95 are shown on the right or below “ / ” at nodes.

Figure 5. Morphological features of Lactocollybia polyhabitata (MFLU 24-0390, holotype) a, b fresh basidiomata in the field c pileipellis in 5 % KOH d transverse section of pileipellis e – h basidioles with crystalline content i, j cheilocystidia k transverse section through stipitipellis l basidiospore. Scale bars: 20 μm (c, d, i); 10 μm (e – h, j – l).

Figure 6. Micromorphological features of Lactocollybia polyhabitata (MFLU 24-0390, holotype) a basidiospore b basidia c basidiole with crystalline content d cheilocystidia e transverse section through pileipellis f transverse section through stipitipellis showing gloeocystidia and caulocystidia in stipe. Scale bars: 10 μm (a – f).