Usnea kriegeriana A. Gerlach & P. Clerc, sp. nov.

Index Fungorum number: IF 900342; Mycobank number: MB 900342; Facesoffungi number: FoF 14476; Fig. 1

Etymology – In honor of the Brazilian Priest Leopoldo Krieger, retired botany teacher of the Federal University of Juiz de Fora (Brazil), who collected many Usnea specimens chiefly in the south of Minas Gerais and in the Paraná State. The oldest specimen of this new species was collected by him in 1975.

Holotype – 2016/P19 (ICN).

Diagnosis – Thallus shrubby, basal part with annular cracks, lateral branches not constricted at ramification point, main branches covered with eroded tubercles and convex soralia, cortex mat, thin to±thick (6.5–)7.5–9%–10.5(–11.5) and medulla with fumarprotocetraric acids as main medullar secondary metabolite.

Lichenized Ascomycota fungi corticolous on bark of Araucaria angustifolia, on exotical Pinus spp, or lignicolous on fences. Thallus shrubby, up to 10 cm long; ramifications mainly isotomic-dichotomous; basal part up to 0.5 cm long, concolorous to the main branches, sometimes paler or with a faint orange tinge, regularly with annular cracks; main branches up to 1.8 mm diameter (n=16), cylindrical to slightly irregular; branches segments cylindrical, sometimes slightly swollen; lateral branches not (main branches) to sometimes slightly constricted (secondary branches) at ramification point; annular cracks present, thin, often with medullar extrusions, sparse to frequent on the whole thallus, 1–2 annular cracks/0.5 cm; foveolae, depressions, maculae and pseudocyphellae absent; papillae absent or sparse; tubercles present, often numerous, verrucous, eroded at top; fibrils slender, unevenly distributed; fibercles sparse; soralia punctiform to large, convex, often circular or building elliptical to irregular masses of soralia, usually numerous on main branches, well delimited to confluent towards the apices of the branches, arising from the top of tubercles, with granular soredia; isidiomorphs usually numerous; isidiofibrils rare; apothecia and pycnidia not seen; cortex moderately thin to ± thick [(6.5–)7.5–9%–10.5(–11.5)], mat (n=16); medulla±thin to thick [19–25.5%–32(–48)], dense; axis sometimes with an orange tinge, thin to±thin [(19–)24–31.5%–38.5(–40)]; A/M =0.6–1–2. Photobiont trebouxioid. Medulla K +yellow turning red. Secondary chemistry detected by thin layer chromatography: fumarprotocetraric acid,±protocetraric acid,±an unknown substance orange after charring Rf classes A/B/C: 1–2/2–3/1–2 (US2) (n=20).

Material examined – Brazil, Santa Catarina: Alfredo Wagner, Reserva Particular do Patrimônio Natural Rio das Furnas, ca. 27° 40′ 28.3″ S, 49° 10′ 37.9″ W, ca. 900 m, on twigs, 13 May 2016, Gerlach et al., 2016/P19 (ICN, holotype), Bosque das Araucarias, sobre Araucaria angustifolia, ca. 900 m, 2016, Gerlach et al. P37 (G); Joinville, estrada das Laranjeiras, sobre mourão, 5 October 2013, Gerlach & Beilke 1133a (ICN); Urubici, Parque Nacional de São Joaquim, arredores do alojamento, ca. 1300 m, 03 February 2014, Gerlach & Alves 1327 (ICN); São Bento do Sul, APA Rio Vermelho, on Araucaria angustifolia, 12 March 2013, Gumboski 4269 (ICN). Espírito Santo, Domingos Martins, in Weide am Morro do Cruzeiro, 1200 m, 20° 26′ S, 41° 00′ W, 11 October 1988, Schäfer-Verwimp & Verwimp (G). Minas Gerais, Serra de Ibitipoca, 19 May 1975, Krieger 13474 (JPB). Paraná: Curitiba, en allant vers Vila Velha, 25°21’S, 49°34’W, 4 March 1989, Grundlehner (G). Rio Grande do Sul: Cambará do Sul, Parque Nacional dos Aparados da Serra, Cânion do Itaimbezinho, 30 April 1989, Fleig 3577 (ICN); ibid., mata nebular próximo ao centro de visitantes, 14 March 2014, Gerlach & Akkerman 1403 (ICN). São Paulo, Zwischen Guapira und Apiaí, in einem Kleinen Pinus-Forest, an Pinus spec., 800 m, 23 August 1980, Kalb (G); Serra da Mantiqueira, Campos do Jordão, etwa 150 km nordöstlich von São Paulo, an freistehenden Pinus spec. 1700 m, 26 May 1978, Kalb & Plöbst (G).

GenBank number – ITS=MF669873.

Notes – Usnea is a ultradiverse genus with more than 450 species worldwide (Lücking et al. 2020) mainly corticolous species in Africa (e.g. Swinscow and Krog 1979; Temu et al. 2019), Europe (e.g. Clerc 1987, 2011; Halonen et al. 1998; Clerc and Otte 2018), Asia (e.g. Ohmura 2001, 2012; Stevens 2004; Ohmura and Clerc 2019), South America (e.g. Rodriguez et al. 2011; Truong et al. 2011, 2013; Truong and Clerc 2012, 2013, 2016; Gerlach et al. 2017, 2019a, b, 2020) and North America (e.g. Clerc 2007; Herrera-Campos 2016). The genus is characterized by the fruticose thallus, branches holding a central axis and the presence of usnic acid in the cortex (Clerc 1998). Usnea kriegeriana is characterized by the annulate and cracked basal part, the lateral branches that are not constricted at attachment point, the numerous tubercles eroded at the top, the large soralia, the mat cortex, the thin to thick medulla (22.5–25%–35) and the presence of fumarprotocetraric acid as main secondary substance in the medulla. The density of the annular cracks with medullar extrusion and isidiomorphs is variable in this species. The lateral branches are most of the time not constricted; only rarely slightly constricted at attachment point. The shape of the segments varies from slightly swollen to cylindrical. Soralia are convex and often well delimited on main branches. Well-developed specimens have confluent soralia that become larger up to the half of the branches diameter towards the apices. Usnea kriegeriana produces fumarprotocetraric often accompanied by protocetraric acid and an unknown substance (refereed as US2; only one specimen without protocetraric and another one without US2 were found) in the medulla.
Usnea kriegeriana is morphologically similar with U. flammea, which, however, differs mainly by the shape of the soralia, that are even with the cortex surface, and by the absence of tubercles (Clerc 2006). Usnea subflammea is similar by the presence of numerous tubercles, but it differs by the thicker cortex [12–16%; instead 7.5–9%–10.5(–11.5) in U. kriegeriana] and the soralia that do not enlarge (Clerc 2006). Moreover, U. flammea and U. subflammea have stictic acid in the medulla whereas U. kriegeriana has fumarprotocetraric acid. Moreover, Usnea kriegeriana builds a strongly supported clade, unrelated to Usnea flammea and U. subflammea (Fig. 2 as Usnea sp. 5 in Gerlach et al. 2019a).

Figure 1 – Usnea kriegeriana. a basal part with annular cracks (white arrows) ((2016/P19, holotype). b lateral branches slightly constricted at ramification point, with annular cracks (arrows) (Krieger 13474). c section through thallus with matt cortex (holotype). d large and confluent soralia (Krieger 13474). Scales bars: a, b=2 mm, c=500 μm, d=2 mm

Figure 2 – Maximum likelihood (ML) tree reconstruction, on RAxML Black Box on the CIPRES server. Outlined on yellow gradient is the outgroup. The new species are in blue. Specimens of Usnea used in the study including voucher information, chemotype and GenBank
accession numbers for the nuclear ribosomal internal transcribed spacer region (ITS) are available on supplementary information