Leucoagaricus nzumbae C. Heisecke, A.A. Carvalho & M.A. Neves, 2021

Heisecke, Celeste, Barbosa, Jaime Andrés Duque, Neves, Maria Alice & Jr, Anibal Alves De Carvalho, 2021, Taxonomic and nomenclatural novelties in Leucoagaricus (Agaricaceae) from Brazil, Phytotaxa 494 (1), pp. 42-58 : 52-54

Leucoagaricus nzumbae C. Heisecke, A.A. Carvalho & M.A. Neves sp. nov. ( Figs 3C , 6A–C )

MycoBank: ― MB 835923

Type:― BRAZIL. Rio de Janeiro: Teresópolis, Parque Nacional da Serra dos Órgãos, first part of the Pedra do Sino trail, 22°27’02.7”S, 43°00’06.3”W, 09 December 2016, Heisecke & Duque, C.H.C. 348 (holotype RB) .

Pileus 10–13 mm diameter, hemispherical, planeo-convex or applanate, sometimes umbonate; surface dry, smooth and brown at the center (6E8), then splitting radially and forming brownish orange fibrillose scales (6C5) on a white to yellowish-white background (1A1, 1A2); margin entire, straight, exceeding the lamellae; context less than 1 mm broad, white, not changing when damaged. Lamellae free, ventricose, 1–3 mm wide, white to yellowish; edge entire, concolorous with the sides. Stipe 20–30 × 2–3 mm, central, cylindrical, fistulose; surface fibrillose, white. Annulus superior to central, membranous, fragile, easily detachable, ascending, white. The entire basidiome turns lilac when dried (15B4, 15C4).

Basidiospores 5.2–6.9 × 3.3–4.8 µm (Q = 1.29–1.91), broadly ellipsoid to oblong, ovoid in side view, uniguttulate, yellowish in water, paler or hyaline in KOH, dextrinoid, metachromatic, thin-walled, without a germ pore. Basidia 17.5–30 × 6.6–9.3 µm, clavate, 4-spored. Cheilocystidia absent. Pleurocystidia absent. Pseudoparaphyses absent. Hymenophoral trama subregular, subhymenium cellular. Pileus covering made up of upright trichodermal elements, 19.8–67.9 × 4.7–9.8 µm, cylindrical to irregular, often tapering upwards with obtuse apex, thick-walled, with brown intracellular and parietal pigments, often encrusted, brown in water and paler in KOH. Scattered oleiferous hyphae present in the pileus context. Clamp connections absent.

Paratypes:— BRAZIL. Rio de Janeiro: Teresópolis, Parque Nacional da Serra dos Órgãos , first part of the Pedra do Sino trail, 22°27’02.7”S, 43°00’06.3”W, 09 December 2016, Heisecke & Duque, C.H.C. 349 (RB, FLOR) ; idem, 11 December 2016, Heisecke & Duque, C.H.C. 365 (RB) ; idem, 19 December 2017, Heisecke & Duque, C.H.C. 498 (RB) ; idem, 16 March 2019, Heisecke & Duque, C.H.C. 525 (RB) .

Etymology:— In honor of Nzumba, a deity from the Afro-Brazilian religion Candomblé Bantu, who dresses in purple and has mud as his representative element. This name was chosen because the type was collected alongside an imperial trail, probably built by slaves, the muddy habitat of the species and the purplish color of the basidiomes when dry.

Distribution and habitat:— Solitary in small groups, in the shade on moist ground among litter and clay, in tropical cloud forest in the Atlantic Forest in Rio de Janeiro State.

Taxonomy:— This species can be recognized by the small basidiomes that turn completely lilac when dried, the brownish color of the pileus surface, and the trichodermal elements with intracellular and parietal brown pigments in the pileus covering.The lack of cheilocystidia is unusual for Leucoagaricus species. However, after exhaustive analyses of all basidiomes collected, not a single cystidium was found, and the lamella edge is formed only by basidioles and basidia.

Due to the small size of the basidiomes ( Fig 3C , pileus 10–13 mm wide and stipe 20–30 mm long), La. nzumbae resembles specimens of Lepiota , but the basidiospores are metachromatic and clamp connections are absent in the entire basidiome ( Fig 6A–C ).

Based on molecular data, La. nzumbae was retrieved in a strongly supported clade along with other species that also change color on drying. The clade is formed by a Mexican specimen labeled as Leucoagaricus cf. coerulescens ( Peck 1899:63) J. F. Liang, Zhu L. Yang & Xu (2010: 1147) , an undescribed species from Hawaii (ecv3754 and ecv3757), and the Asian species Leucoagaricus viriditinctus ( Berkeley & Broome 1871: 503) J.F. Liang, Zhu L. Yang & J. Xu in Liang et al. (2010: 1146), characterized by their basidiomes that turn bluish green when dehydrated, which is quite different from La. nzumbae which turns lilac.

The color changes of the basidiomes in response to bruising or drying are important characteristics for the taxonomy of Lepiota s.l. ( Reid 1990, Liang et al. 2010, Vellinga 2006, 2010, Vellinga et al. 2010). The lilac tint of La. nzumbae when dry is like that found in other representatives of Leucoagaricus . Leucoagaricus lilaceus , originally reported for Argentina and then Brazil ( Sobestiansky 2005, De Meijer 2006, Rother & Silveira 2008, 2009, Ferreira & Cortez 2012), has a robust fleshy basidiome with whitish lamellae that turn pinkish with age and when dried, and the stipe base is abruptly bulbous with rhizomorphs ( Singer & Digilio 1952, Rother & Silveira 2009). Leucoagaricus variicolor , from Spain, has yellowish to ochraceus-cream, volvate, fleshy basidiomes that turn pinkish when dried and has spheropedunculate cheilocystia ( Muñoz et al. 2012). Lepiota roseolivida Murrill (1912: 234) from the U.S.A. also has delicate basidiomes that turn lilac when dried, but the pileus surface is livid to dull rose-lilac when fresh, which is different from the brownish color on a whitish background present in La. nzumbae . Lepiota roseolivida also has larger amygdaliform basidiospores (6.7–9.8 × 3.8–5.7 μm) and clavate cheilocystidia ( Murrill 1912, Vellinga 2006).

Some species of Leucoagaricus described from Brazil show morphological affinities to La.nzumbae : Leucoagaricus confusus ( Rick 1937: 341) Singer (1951: 422) , Leucoagaricus imperialis ( Spegazzini 1889: 382) Pegler (1997: 33) and Leucoagaricus tricolor Singer (1989: 98) . Both La. confusus and La. tricolor have small basidiomes as in La. nzumbae (pileus diameter <20 mm,) ( Rick 1937, Singer 1951, 1989). However, La. confusus could be differentiated by a yellowish pileus surface, absence of reaction when damaged or dried, and bigger basidiospores (10 × 5 μm) ( Rick 1937, Singer 1951); and La. tricolor , by the reddish-brown pileus surface, lamella color that changes from grey to brownish grey on drying and the fasciculate pileus covering ( Singer 1989). Meanwhile, Leucoagaricus imperialis ( Spegazzini 1889: 382) Pegler (1997: 33) has a brownish pileus surface as in La. nzumbae , but differs from it by the bigger basidiomes (pileus 40−50 mm diameter, stipe 100 × 4−5 mm) that are mostly whitish and change to brownish when dried, and the larger basidiospores (8−12 × 5.5−6.5 μm) ( Spegazzini 1889, Pegler 1997).

Another Leucoagaricus species reported from Brazil and morphologically related to La. nzumbae is Leucoagaricus sulphurellus ( Pegler 1983: 420) B.P. Akers in Akers, Angels & Kimbrough (2000: 48), described from the Caribbean islands ( Pegler 1983, 1997, Wartchow et al. 2008, Rosa & Capelari 2009). This species shares the small basidiome (pileus 8−21 mm diameter) and the brownish pileus surface with La. nzumbae , but it differs by its sulphur yellow basidiome, that changes color to pinkish brown and then blue-green when damaged, basidiospores with a germ pore, and the appressed pileus covering ( Pegler 1983, Akers et al. 2000).

Figures

FIGURE 3. Photographs of fresh basidiomes in situ. A–B. Leucoagaricus gongylophorus C.H.C. 463 (Epitype). B. Detail of the base of the stipe attached to the fungal garden of leaf-cutting ants. C. Leucoagaricus nzumbae C.H.C.349 (Holotype). Scale bars are 50 mm for A and B and 10 mm for C. Photos by C. Heisecke.

FIGURE 6. Leucoagaricus nzumbae C.H.C.349 (Holotype). A. Basidiospores. B. Basidia. C. Elements of the pileus covering. Scale bars are 10 µm. Illustration by C. Heisecke.