Introduction
The Atlantic rainforest, or Mata Atlântica, despite centuries of deforestation and destruction, still harbours the highest biodiversity per hectare of any tropical rainforests on the planet (Conti & Furlan Reference Conti, Furlan and Ross2003). The Serra da Jibóia is a mountain range with a maximum elevation of 800 m, in a transitional area between Atlantic forest and Caatinga vegetation, which is a drier and more open forest type.
This Mata Atlântica fragment is located in the Santa Terezinha municipality, Bahia, NE Brazil, near the Castro Alves municipality boundary. This area can be considered a rainforest enclave surrounded by Caatinga, and belongs to a disjunct set of mountains that extends from the southern coast of the state to the north-west and north until the Baia de Todos os Santos region (Queiroz et al. Reference Queiroz, Sena and Costa1996).
Within the framework of a recent survey of lichens in rainforest enclaves in areas of Caatinga throughout north-eastern Brazil, an undescribed species of Micarea was found and is described below as new to science.
The genus Micarea in the family Pilocarpaceae is still incompletely known, with c. 90 known species worldwide (Coppins Reference Coppins, Smith, Aptroot, Coppins, Fletcher, Gilbert, James and Wolseley2009). The new Micarea species differs from all species known so far in the genus by the irregularly-branched isidioid structure of the thallus and the aggregated ascomata with curved, mostly 1-septate ascospores.
Material and Methods
Identification and descriptive work was carried out in Itabaiana, Universidade Federal de Sergipe, using a Leica EZ4 stereomicroscope and a Leica DM500 compound microscope, and also in Soest using an Olympus SZX7 stereomicroscope and an Olympus BX50 compound microscope with interference contrast, connected to a Nikon Coolpix digital camera. Sections were mounted in tap water, on which all measurements were taken. The specimen from this study is preserved in ISE. The chemistry of the type specimen was investigated by thin-layer chromatography (TLC) using solvent A (Orange et al. Reference Orange, James and White2001).
The Species
Micarea corallothallina M. Cáceres, D. A. Mota & Aptroot sp. nov.
MycoBank No.: MB 801124
Micarea with an irregularly-branched isidioid structure of the thallus and aggregated botryose ascomata with curved, mostly 1-septate ascospores. Thallus and apothecia are devoid of pigment, and no lichen substances are present.
Type: Brazil, Bahia, Santa Teresinha, Serra da Jobóia, on bark of tree, c. 700 m alt., September 2010, M. E. S. Cáceres 7886 (ISE—holotype).
(Fig. 1)
Fig. 1. Micarea corallothallina (holotype). A & B, habitus; C, isidioid thallus granules; D, section through ascoma; E, ascus; F & G, ascospores. Scales: A & B=1 mm; C=50 µm; D=10 µm; E–G=5 µm. In colour online.
Thallus 0·2–0·4 mm thick, dull, consisting of isolated, irregularly densely branched isidioid green granules of c. 50 µm thick (proliferating goniocysts somewhat like blastidia), with a hyaline cortex. Algae myrmecioid, c. 3–5 µm diam.
Apothecia appressed, initially between the thallus granules, later often emergent, up to 0·2 mm diam., usually aggregated in botryose groups of 2–25, forming clusters of up to 1·2 mm diam.; disc globose, pale yellowish. Hymenium hyaline, 25–35 µm high, paraphyses glued and sparse; hypothecium hyaline; excipulum inconspicuous. Ascus with 8 ascospores, arranged in 2 loose bundles. Ascospores hyaline, curved, (0–)1-septate, 15–17×3·0–3·5 µm, with rounded ends.
Pycnidia not observed.
Chemistry
Thallus and apothecia UV−, C−, K−, KC−, P−. No pigments visible and no lichen substances detected with TLC.
Ecology and distribution
On smooth bark of trees in primary forest. Known only from Brazil.
Discussion
The thallus of this species is very unusual, both in and outside the genus because of its irregularly branched, nodular isidioid structure and the aggregated (botryose) ascomata. Species of the genus Micarea occur in all biospheres including wet lowland tropics, but most species described so far are from temperate or arctic/alpine environments. The new species probably belongs in the Micarea prasina group, members of which can have an isidioid thallus (Coppins Reference Coppins1983, p. 175; Czarnota Reference Czarnota2007, p. 100), as well as botryose (tuberculate) apothecia, and 0–1-septate ascospores. However, most members of the group have the green-grey, K+ violet pigment, Sedifolia-grey, as well as lichen substances in the thallus and/or apothecia. Somewhat similar to the new species is Micarea levicula (Nyl.) Coppins from Cuba, but that species has a C+ red thallus (containing gyrophoric acid) and smaller ascospores, 8–12×2·5–3·5 µm (van den Boom & Coppins Reference van den Boom and Coppins2001). In addition, some morphs of Micarea micrococca can become isidiose, but that species also has smaller ascospores, and contains methoxymicareic acid (Czarnota & Guzow-Krzemińska Reference Czarnota and Guzow-Krzemińska2010).
The CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) is thanked for a research grant to MESC (Processo 501633/2009-0) and to LSJ (Processo 505312/2010-7). The collecting expedition was financed by the PPBIO/Semiarid project (CNPq processo 558317/2009-0). Leo Spier is thanked for performing thin-layer chromatography. AA is grateful to the Stichting Hugo de Vries-Fonds for a travel grant. An anonymous referee is warmly thanked for providing detailed elements of the discussion.
