Caloplaca nigrocarpa Pérez-Vargas & C. Hdez.

Pérez-Vargas, Israel, González-Montelongo, Cristina, Padrón, Consuelo Hernández & Paz, Pedro Luis Pérez De, 2015, A new species in the lichen genus Caloplaca from the Canary Islands, including a key to all brown-black Caloplaca sensu lato species in Macaronesia, Phytotaxa 205 (3), pp. 205-210 : 206-208

Caloplaca nigrocarpa Pérez-Vargas & C. Hdez. -Padr. sp. nov. ( Fig. 1 )

Thallus crustaceus, epiphloeodeus, continuus vel areolatus, griseus vel brunneo-olivaceus, K-. Apothecia numerosa, dispersa, sessilia, orbicularia, ad 0.2–0.4 mm in diametro. Disco subconcavo vel plano, badio-fusco vel nigro, epruinoso. Margo propius bene evolutus, nitidulus demum subflexuosus. Hymenium 50–70 μm altum, hyalinum; hypothecium incoloratum. Paraphyses simplices vel parce ramosae, simulac capitatae, apicibus usque ad 2–4 μm latis. Asci 8-spori, clavati, typi “ Teloschistes ” dicti. Ascosporae hyalinae, polariloculares, ellipsoideae vel ovoideae (9.8–) 13.4–14.3 (–16) × (5–) 6.8–8.2 (–10) μm, septo regul. (5–) 6.4–7.6 (–9) μm, ½ longitudinis lato. Conidiomata ignota.

MycoBank No.: 810384

Type: — SPAIN. Canary Islands: La Palma, Caldera de Taburiente National Park, “Playa de Taburiente”, 850 m alt., on Salix canariensis , March 2005, P. L. Pérez de Paz 5825 (holotype: TFC-Lich!).

Thallus corticolous, crustaceous, epiphloeodal, continuous to slightly areolate at margin, pale gray to olive greenishgrey, with a blackish prothallus, lacking isidia and soredia. Photobiont green, coccoid, cells up to 7–8 μm in diameter. Ascomata apothecia, 0.2–0.4 mm in diam., rounded, adnate; disc concave at first then flat, epruinose, dark brown to black; thalline margin absent; proper margin persistent, slightly flexuose when mature, epruinose, shiny. Exciple distinct, 20–40 μm, formed by radiating, prosoplectenchymatous hyphae; outer part of the exciple brownish, inner part not pigmented; epihymenium greenish-bluish, K –, N + reddish, becoming discolored with C; hymenium hyaline, 50–70 μm, clear; paraphyses simple to irregularly branched in upper part, middle hymenium cells 1.5–2.5 μm, not or slightly swollen in apical part, up to 3–4 μm thick; subhymenium hyaline; asci cylindrical, Teloschistes - type, 33–38 μm, 8-spored; ascospores polarilocular, ellipsoid and colorless (9.8–) 13.4–14.3 (–16) × (5–) 6.8–8.2 (–10) μm, septum (5–) 6.4–7.6 (–9) μm, about ½ of length of spore. Conidiomata not seen.

Chemistry: —Thallus and apothecia K –, C –, KC– Pd– and UV –; no lichen substances found by TLC.

Ascomatal pigments were analyzed in accordance with standardized procedure proposed by Meyer & Printzen (2000). However, none of the pigments described matched with the blue-green pigment found in Caloplaca nigrocarpa .

Etymology: —The specific epithet nigrocarpa refers to the dark color of the apothecia.

Distribution and ecology: —So far, the new taxon is only known from the type locality in La Palma. It occurs on bark of trunks of canary willow ( Salix canariensis C. Sm. ex Link , a Macaronesian endemic) in the ravine of La Caldera de Taburiente National Park. The canary willow stand is a heliophilous community (Rubo - Salicetum canariensis ) characterized by Salix canariensis , typical of the banks of streams flowing most of the year, and also near springs. Morella faya (Aiton) Wilbur is the only tree species accompanying the canary willow. The bramble Rubus ulmifolious Schott and the invasive Ageratina adenophora (Spreng.) R. M. King & H. Rob and A. riparia (Regel) R. M. King & H. Rob are common ( Del Arco et al. 2010). The new species is extremely localised, and has been found only in the willow grove in Taburiente ravine; searches in similar habitats in the general vicinity, as well as further afield such as on other islands in the Canaries and in other Macaronesian archipelagoes (Madeira and Azores) have failed to reveal any further localities (but we do not discard its occurrence). Thus, it represents an extremely uncommon taxon of high conservation value, especially as much of the site where it grows, a canary willow copse. The canary willow community has retreated greatly in the Canary Islands, and only persists in less than 22% of the potential distribution area in the archipelago, and in some places with little possibility of recovery ( Del Arco et al. 2010). Caloplaca nigrocarpa was found growing together with Caloplaca holocarpa (Hoffm.) A. E. Wade , Lecanora chlarotera Nyl. and Rinodina capensis Hampe.

Discussion: —The new species has a peculiar combination of characters not observed in other species of the same group. Morphologically, the most similar species are the Eurosiberian Parvoplaca suspiciosa (Nyl.) Arup, Søchting & Frödén and the tropical American Caloplaca floridana (Tuck.) Tucker (Wetmore com. pers.). The epihymenium of both species is grey (occasionally brown) and K+ purple. Also, C. floridana has an apothecial margin K+ violet, N+ violet and cN+violet ( Wetmore 2007) with thin end walls in the ascospores. Caloplaca suspiciosa in addition has smaller ascospores (10–11 × 5.5–7 μm, isthmus 3–4 μm) ( Wetmore 1994).

Other epiphytic species with similar morphology, dark apothecia and ascospores size include C. fuscoblastidiata van den Boom & Etayo and C. catillarioides Arup & van den Boom. The former is a maritime species from southwestern Europe ( Portugal and Spain) with coralloid to cylindrical blastidia and different chemistry ( van den Boom & Etayo 1995). The latter is a recently described endemic from the Cape Verde islands with blackish K+ purple-brown to violet epihymenium, slightly different ascospores (narrower septum and different ecology), growing on volcanic rocks in arid areas ( Arup & van den Boom 2011) ( Table 1).

Figures

FIGURE 1. Habitat and morphology of Caloplaca nigrocarpa. A. Canary willow in “Taburiente Ravine”; B. Habit; C. Apothecia; D, E Hymenium (in water); F. Hymenium (in HNO3); G. Ascus; H, J, K, L & M. Ascospores. I. Paraphyse. Scale bars: B: 1 cm; C: 0.5 cm; D, E, F: 50 μm; G: 20 μm; H: 25 μm; I, J, K, L, M: 10 μm.