Saxiloba firmula (Nyl. ex Müll. Arg.) Lücking, Moncada & Sipman, comb. nov. (Fig. 2)
MycoBank number: MB 835481; Index Fungorum number: IF 835481; Facesoffungi number: FoF 13232;
≡ Porina firmula Nyl. ex Müll. Arg., Bot. Jb. 6: 401. 1885; Verrucaria firmula Nyl., Flora 59: 365. 1876.
Type: Cuba. Unknown locality and date, C. Wright s.n. (G-G00293637, lectotype!, here designated; Lich. Cub. 7b; isolectotypes: G-G00293636, G-G00293638; Lich. Cub. 7).
= Endopyrenium incrassatum Müll. Arg., Bot. Jb. 6: 377 (1885); Dermatocarpon incrassatum (Müll. Arg.) Zahlbr., Cat. Lich. Univers. 1: 218. 1921 .
Type: Cuba. Unknown locality and date, C. Wright s.n. (G-G00291774, lectotype!, here designated; Lich. Cub., Ser. II: 535; isolectotype: G-G00291775; Lich. Cub., Ser. II: 535).
Description. Thallus saxicolous on calcareous rocks, up to 5–10(–20) mm diam. with regularly radiating lobes with closely contiguous tips; lobes 0.5–0.1 mm wide; surface silvery grey-green with a network of reticulate lines around isodiametric to elongate chambers (best seen when hydrated). Thallus in section 200–300 μm thick with large, up to 100 μm high and broad, triangular to rhomboid crystal clusters embedded into the photobiont layer, the latter developed horizontally beneath and vertically between the crystal clusters; above with a 20–30 μm thick, prosoplectenchymatous cortex and below with a 30–50 μm thick medulla and a 40–70 μm thick, dark brown hypothallus layer. Perithecia erumpent from the thallus and almost up to the ostiolar area covered with a thick thallus layer, up to 0.5 mm diam.; excipulum 25–35 μm thick, outer parts paraplectenchymatous, pale yellowish, K+ deep orange-red, inner parts prosoplectenchymatous, colourless; involucrellum only developed around the ostiolar area, 30–60 μm thick, paraplectenchymatous, reddish brown with a distinct reddish tinge when seen from the outside. Ascospores 8 per ascus, oblong-fusiform, transversely 3–5(–7)-septate, 15–20(–25) × 3–4(–6) μm, hyaline. Pycnidia rare, up to 0.1 mm diam., appearing as brownish red warts. Conidia oblong-bacillar, non-septate, 3–4 × 1 μm, hyaline
Distribution and ecology. Thus far known from Cuba, including Isla de la Juventud (also known as Isle of Pines or Isla de Pinos) and further reported from the Baha- mas and Puerto Rico (Müller 1885; Riddle 1923; Gannutz 1970; Mercado-Díaz 2009). Possibly a Caribbean endemic, in Cuba quite common on calcareous rocks in mostly shaded microhabitats in the dry forests of western and central Cuba. In Puerto Rico, it would be expected in similar habitats, but has not been found in recent surveys. According to Gannutz (1970), the Puerto Rican material was collected at El Yunque National Forest, a rather wet forest with a geology dominated by volcanic rock. This would broaden the ecological range for Saxiloba firmula, but since we have not been able to obtain the material corresponding to this record, we are considering these data with care.
Notes. Saxiloba firmula was first introduced as nomen nudum by Nylander (1876) in the genus Verrucaria and shortly after validated by Müller (1885) in the genus Porina. Müller (1885: 401) did not properly describe the unique thallus morphology of the species, likely because the type material had originally been scraped off the substrate and is fragmented into numerous, small pieces in the lectotype and isolectotypes. Müller (1885: 377) described the same species also as Endopyrenium incrassatum, possibly because of the few, young ascomata (‘apothecia pauca valde juvenilia offerunt’) with small (18–20 × 4–6 μm), 1-septate ascospores, not realizing the identity of the mate- rial. McCarthy (1993) did not mention the name in his treatment of saxicolous Porina species; he annotated the type material in 1992 as ‘probably not Porina’. Riddle (1923) reported the species from Isla de la Juventud (Isle of Pines). One of the two cited collections was reported as ‘… Cerro San Juan del Mar, Columbia…’ (Riddle 1923: 71), which may cause confusion, as there is indeed such a location in Colombia. However, the material refers to Cerros de San Juán in the Columbia community on Isla de la Juventud (Kallunki 1980; Boom 1996; Sastre de Jesús & Santiago-Valentín 1996). In the same paper, Riddle (1923) described P. subfirmula Riddle, also from Isla de la Juventud. That species has, however, a very different, crustose thallus morphology (isotype in NY, NY01219352, Britton & Wilson 15741 checked).
Müller (1885) described (and illustrated the ascospores on the type material as predominantly 5-septate and 20–30 μm long. In our recently collected material, we found only few thalli with perithecia with the ascospores mostly 3-septate and 15–20 μm long. Annotations on NY specimens by R.C. Harris also indicate 3-septate ascospores and a discrepancy with Müller’s description (J. Lendemer, pers. comm. 2020). Revision of the lectotype showed the ascospores to be mostly 3-septate, more rarely 4–5-septate, and 15–20(–25) μm long. It is therefore unclear how Müller (1885) derived his observations, although based on annotations by R. C. Harris, the material from the Bahamas apparently also features ascospores with more numerous septa (J. Lendemer, pers. comm. 2020).
Specimens examined. BAHAMAS. Andros, Mastic Point and Vicinity; 25°03’N, 77°57’W; 19–28 March 1907, L. J. K. Brace 7048a (FH). Cockburn Town, Watling’s Island; 12–13 March 1907, N. L. Britton & C. F. Millspaugh 6126 (FH). CUBA. The type material of P. firmula and E. incrassatum. Artemisa: Candelaria, Jardín Botánico Orquideario Soroa; 22°47’N, 83°01’W, 210 m; on shaded calcareous rock face; 24 March 2017, R. Lücking & B. Moncada 43034 (B, HAJB). Cienfuegos: Cumanayagua, Las Vegas del Matagua, trail from Lucia’s house to Las Lagunas; 21°59’14″N, 80°11’54″W, 665 m; evergreen lower montane (mesophyllous) rain forest, on calcareous rock; 21 March 2018; R. Lücking & B. Moncada 45155 (B, HAJB), 45157 (B). Caletón de Don Bruno, trail from town towards coastal mangrove; 22°04’16″N, 80°27’44″W, 0–25 m; matorral costero, on calcareous rock; 22 March 2018, R. Lücking & B. Moncada 45298 (B). Pinar del Río: Rio Guao; 27 February 1911; N. L. Britton et al. 9668 (FH). Viñales, Pinar del Río National Park, Sierra de Quemado, Moncada, 20 km WSW of Viñales, ‘mogote’ behind Malagones monument; 22°33’N, 83°51’W, 180 m; mesophyllous semideciduous forest on karst, on calcareous rock face; 9 April 2016, R. Lücking et al. 41865, 41891 (B, HAJB). Sancti Spiritus: Trinidad, Parque Natural Protejido Topes de Collantes, trail to Pico de Potrerillo; 21°53’17″N to 21°54’19″N, 80°00’11″W to 80°00’31″W; 650–860 m; on calcareous rock; 19 March 2018, R. Lücking & B. Moncada 44918 (B). Isla de la Juventud: SW of Nueva Gerona, Sierra de Casas, Mogote El Abra; 21°85’N, 82°82’W; April–May 1975, R. Schubert (B, HAL). Cerro San Juán del Mar; 20 February 1916, N.L. Britton & P. Wilson 14683 (FH, NY). Cerros de Bibijagua; 28 February 1916, N.L. Britton & P. Wilson 15047 (FH, NY).
Figure 2. Habit of Saxiloba firmula. A – thallus on calcareous rock; B – young thallus with immature perithecia; C–D – thallus lobes hydrated (in D enlarged) to show crystal clusters embedded in a network of hyphae with the photobiont layer beneath; the crystals reflect the greenish color of the photobiont, whereas the pale color of the reticulate lines is caused by the upper cortex; E – thallus section showing disposition of crystal clusters, photobiont layer, upper cortex, medulla and hypothallus; F – perithecia; G – section through perithecium showing laterally covering thallus layer with details of crystal clusters H, ascus with ascospores. (A – Lücking et al. 41865; B–D – Lücking et al. 41891; E–G – Lücking & Moncada 45298; H – lectotype). Scales: A = 5 mm; B–C, F = 1 mm; D = 0.5 mm; E, G = 100 μm; H = 10 μm.