Green, apotheciate species of the genus Sticta are among the most misunderstood lichens in terms of their taxonomy. To date, most samples at a worldwide level have been identified as S. canariensis (Bory) Bory ex Delise and more commonly as S. damicornis (Sw.) Ach. (Durand & Pittier Reference Durand and Pittier1891; Hitchcock Reference Hitchcock1898; Schiffner Reference Schiffner1901; Riddle Reference Riddle1912; Merrill Reference Merrill1913; Howe Reference Howe1914; Plitt Reference Plitt1921; Malme Reference Malme1934; Welch Reference Welch1950; Herre Reference Herre1951; Imshaug Reference Imshaug1956; Zahlbruckner Reference Zahlbruckner1956; Dix Reference Dix1957; Thomasson Reference Thomasson1959; Choisy Reference Choisy1960; Follmann Reference Follmann1976; Tønsberg Reference Tønsberg1990; Wolf Reference Wolf1993; Brodo Reference Brodo1994; Marcano et al. Reference Marcano, Morales-Méndez, Sipman and Calderon1996; Nayaka & Upreti Reference Nayaka and Upreti2005; Holz Reference Holz2006; Sipman Reference Sipman2006; Cerón & Quintero Reference Cerón and Quintero2009; Joshi et al. Reference Joshi, Upreti and Das2011; Martins et al. Reference Martins, Käffer, Alves and Pereira2011; Rincón-Espitia et al. Reference Rincón-Espitia, Aguirre-C and Lücking2011; Benítez et al. Reference Benítez, Prieto, González and Aragón2012; Bungartz et al. Reference Bungartz, Ziemmeck, Ayabaca, Nugra and Aptroot2013; Mishra & Upreti Reference Mishra and Upreti2014; Aptroot Reference Aptroot2016; Nelson & Sandoval Reference Nelson Sutherland and Sandoval2018). To reflect the apparent morphological diversity in these lichens from all parts of the world, numerous infraspecific taxa have been established in a broadly defined S. damicornis, with some authors even including S. canariensis at the level of form or variety (Flörke Reference Flörke1809; Acharius Reference Acharius1814; Nylander 1859 Reference Nylandera , Reference Nylanderb ; Müller Reference Müller1881; Stizenberger Reference Stizenberger1895; Malme Reference Malme1934).
The name Sticta damicornis has frequently been used to identify green-algal Sticta species from the Atlantic Forest of Brazil (da Silva et al. Reference da Silva, Iacomini and Gorin1990; de Oliveira et al. Reference de Oliveira, F., Doná, Marcelli, Cardoso and da Silva2002; Käffer & Martins Reference Käffer and Martins2005; Spielmann Reference Spielmann2006; Käffer et al. Reference Käffer, Ganade and Marcelli2007, Reference Käffer, Ganade and Marcelli2009; Gumboski & Eliasaro Reference Gumboski and Eliasaro2011; Martins et al. Reference Martins, Käffer, Alves and Pereira2011). Molecular data have shown that green-algal species in the Neotropics represent multiple distinct taxa (Moncada et al. Reference Moncada, Coca and Lücking2013, Reference Moncada, Lücking and Suárez2014), particularly in the Brazilian Atlantic Forest where they are represented by several separate, and in most cases endemic, taxa unrelated to the European-Macaronesian S. canariensis and the Caribbean endemic S. damicornis (Moncada et al. Reference Moncada, Mercado-Díaz and Lücking2018). These taxa are restricted to well-conserved areas in the few remnants of the Atlantic Forest and threatened by habitat loss. Here, we recognize a characteristic species with linear, much branched lobes with parallel, straight margins which taper to rounded ends, and apothecia arranged uniquely in dense lines along the margins (Fig. 1A). This lichen was originally described as S. laciniata var. trichophora Müll. Arg., based on three collections from Minas Gerais and Rio de Janeiro (Müller Reference Müller1881). Unfortunately, the use of the epithet trichophora in the genus Sticta is blocked by S. trichophora Vain., an unrelated species described from the Philippines (Vainio Reference Vainio1913). We therefore introduce the replacement name, Sticta aongstroemii.
Sticta aongstroemii Dal Forno, Moncada & Lücking nom. nov.
Index Fungorum IF 554766
Sticta laciniata var. trichophora Müll. Arg., Flora 64: 85 (1881); Sticta laciniata f. trichophora (Müll. Arg.) Stizenb., Flora 81: 122 (1895); type: Brazil, Minas Gerais, Poços de Caldas, Johan Ångström s. n., comm. C. Müller (G-G00295522, lectotype!, selected here) [non S. trichophora Vain., Philipp. J. Sci., C, Bot. 8(2): 123 (1913)].
The epithet of the replacement name honours the collector of the type material, the Swedish bryologist Johan Ångström (1813–1879). Müller (Reference Müller1881) cited three collections in the protologue; one from Rio de Janeiro (Deventer 16) could not be located and another from there (Glaziou 2214) was later described as a different variety, Sticta laciniata var. subdamicornis Müll. Arg. (Müller Reference Müller1891). The specimen from Minas Gerais was therefore selected as lectotype for S. laciniata var. trichophora, now renamed S. aongstroemii.
As outlined above, Sticta aongstroemii is set apart from other green-algal Sticta species by the combination of laciniate lobes with parallel margins and rounded to tapering tips, and particularly the densely arranged, marginal apothecia in combination with a thin but distinct, dark brown lower tomentum contrasting with the conspicuous, whitish cyphellae; the branching pattern is distinctly anisotomous, with the lobes growing at an angle of c. 45–60° (Fig. 1A & B). Sticta damicornis s. str., known from Cuba, Jamaica and the Dominican Republic (Moncada et al. Reference Moncada, Mercado-Díaz and Lücking2018), has much narrower lobes (c. 2 mm wide compared to c. 5–8 mm in S. angstroemii) and scattered apothecia; it corresponds in the dark lower tomentum but its cyphellae are much smaller. Sticta canariensis s. str., which is known with certainty from only western Europe and Macaronesia, matches S. aongstroemii in size and lobe width but differs in the following characters: the lobes branch subdichotomously rather than anisotomously, with truncate tips and generally shorter internodes and the branches growing at an angle of 60–90°; the underside is light to medium (ochraceous) brown with rather small cyphellae not contrasting with the lower tomentum and the apothecia are usually scattered over the lobe surface, becoming more dense towards the margins but usually not in conspicuous, regular lines. The type material of Sticta laciniata var. subdamicornis (Rio de Janeiro, Glaziou 2214), is similar to S. canariensis in most characters, but our molecular data suggest that the latter is not present in the Neotropics or southern Brazil (B. Moncada, E. Sérusiaux, B. Goffinet et al., unpublished data) and that there is a considerable level of cryptic speciation, with high morphological congruence even in unrelated lineages, as is also the case for the names S. fuliginosa and S. weigelii (Moncada et al. Reference Moncada, Lücking and Suárez2014; Magain & Sérusiaux Reference Magain and Sérusiaux2015). We are currently preparing an updated phylogeny of the genus Sticta based on the ITS barcoding locus, which includes numerous green-algal species of Sticta from South America (B. Moncada, E. Sérusiaux, B. Goffinet et al., unpublished data). Our data suggest that none of these species, including the present taxon, is related to either S. canariensis or to the clade that underwent substantial radiation in Madagascar and the Mascarenes, including S. dichotoma Bory, another often misapplied name (Simon et al. Reference Simon, Goffinet, Magain and Sérusiaux2018).
Sticta aongstroemii is one of several potentially endemic green-algal Sticta species in the Atlantic Forest of Brazil, largely restricted to the southern part of this biome, ranging from Minas Gerais to Rio Grande do Sul. The Atlantic Forest ranges among the most diverse ecosystems on Earth, including high levels of endemism (Mittermeier et al. Reference Mittermeier, Myers, Thomsen, da Fonseca and Olivieri1998). It originally covered 13% of Brazil but has been diminished to c. 1%, with high levels of degradation and fragmentation (Brooks & Balmford Reference Brooks and Balmford1996; Ranta et al. Reference Ranta, Blom, Niemelä, Joensuu and Siitonen1998; Ribeiro et al. Reference Ribeiro, Metzger, Martensen, Ponzoni and Hirota2009; Fundação SOS Mata Atlântica & INPE 2009, 2016; Tabarelli et al. Reference Tabarelli, Aguiar, Ribeiro, Metzger and Peres2010). Lobariaceae lichens, particularly green-algal species, are threatened by this dramatic loss of habitat but can also be used as bioindicators to monitor remaining forest fragments for conservation purposes, which is the case for the specimen in Fig. 1A (M. Dal Forno 2812). This sample of S. aongstroemii was observed in a tropical montane cloud forest (also known as Mata or Matinha Nebular) in South-eastern Brazil, in a small forest close to the road, in the surroundings of the touristic city of Campos do Jordão, São Paulo. Despite being small, the area is rich in lichen species, including several undescribed taxa of asco- and basidiolichens. The presence of multiple species of Lobariaceae, including large individuals such as the one shown here, indicates that this forest is a remnant of the once dominant Atlantic Forest in this region. The correct identification of species, such as S. aongstroemii, is crucial in assessing the biodiversity and conservation status of such fragments and this contribution is a first step towards a thorough inventory of the Lobariaceae of this region.
Additional specimens examined. Brazil: São Paulo: Campos do Jordão, road to Pico do Itapeva, Serra da Mantiqueira, 22°45′58″S, 45°32′27″W, 1882 m, Mata Atlântica domaine, montane cloud forest (matinha nebular), along roadside, M. Dal Forno 2812 (with A. Gerlach, P. Clerc & R. Penati).
Funding for this study was provided by a grant from the National Science Foundation (NSF) to The Field Museum: DEB-1354884 ‘Collaborative Research: Evolution, Diversification, and Conservation of a Megadiverse Flagship Lichen Genus’ (PI H. T. Lumbsch, CoPI R. Lücking) and a Postdoctoral Research Fellowship in Biology (PRFB 1609022) to M. Dal Forno. Alice da Cruz Lima Gerlach, Philippe Clerc and Rodrigo Penati are thanked for their additional funding and field support during the Serra da Mantiqueira Usnea-Cora Expedition (Brazil) in November 2017. Philippe Clerc kindly allowed us to use a portion of the digitized type image of Sticta laciniata var. trichophora.