Diagnosis. Differs from other species by its elongated, light bluish grey to olivaceous, occasionally necrotic beige squamules, which can grow into very large thalli.
Type. ECUADOR. GALAPAGOS ISLANDS: Isla Santa Cruz, along trail from Bellavista to El Puntudo, upper Cinchona forest, 0°39′002″S, 90°20′42″W, alt. 684 m. Dense forest of Cinchonapubescens, some life trees but mostly dead trees due to management control of the invasive trees, on bryophyte, growing over Frullania sp., 23 Jun 2010, Dal-Forno, M. 1205 (CDS 44756, holotype; GMUF, F, isotypes).
Description. Thallus microsquamulose; squamules elongated, attached basally to the substrate and proliferating from the tips, and moderately swollen, 0.1–0.2 (–0.3) mm broad, up to 2 (–3) mm long, abundantly branched and typically intricately tiled, many growing together, occasionally thus shading one another, light blue grey to olivaceous when fresh, darker olivaceous grey when dry, the shaded parts becoming necrotic and pale beige to orange. Overall uniform pruinose appearance. Soredia absent. Thallus in cross section 130–160 μm thick, dominated by a thick photobiont layer, and with a thin cortex and medulla. Photobiont Rhizonema, clusters of densely coiled cyanobacterial filaments wrapped within a hyphal sheath formed by jigsaw puzzle-shaped cells (Cora-type). Acanthohyphidia typically small, rarely of moderate size, 12–16 (–20) × 6–10μm, subglobose to pyriform.
Distribution and ecology. All material of Acantholichen collected in Galápagos belongs to the same species and it is considered here to be endemic to this archipelago. In general,specimens do not grow directly on trees or shrubs, but typically establish on epiphytic liverworts and mosses, which in turn are common on a variety of substrates: introduced trees (Cinchona pubescens, Psidium guava), native shrub (Zanthoxylonfagara) and endemic trees (Scalesiapedunculata, Psychotria spp.); one specimen was even collected on a soil inhabiting bryophyte (Campylopus sp.). The populations overgrowing Frullania (Jubulaceae, Marchantiophyta) on the introduced tree Cinchona in Santa Cruz represent the best developed material. The type specimen was collected in this particular habitat, where the endemic Acantholichengalapagoensis is surprisingly abundant. At the type locality, individual thalli are among the largest and best developed specimens known, covering dead tree trunks and forming up to 1 mlength, indicating that the species thrives particularly well in these humid highlands around El Puntudo and Cerro Crocker. In contrast, collections from all other islands are mostly minute and not well developed, with the notable exception of collections from Cerro Azúl (one of the highest and the southernmost volcano of Isabela), where specimens grow exuberant and abundantly on the dead basal sheaths of fronds of the endemic Galápagos tree fern (Cyatheaweatherbyana). Because Cinchona is a tree introduced to the archipelago, one can assume that the endemic, now threatened tree ferns represent the original, natural habitat of this endemic Acantholichen.
Etymology. The epithet refers to the type locality.
Comments. Our phylogenetic studies demonstrate that this species, as many other basidiolichens in the Galápagos, are endemic to the archipelago. The phylogeny places the species as a sister of the clade containing A. campestris and A. variabilis. Its most diagnostic characteristics are the olivaceous thalli of elongated and intricate, often overlapping or “tiled” squamules; this structural arrangement of the squamules immediately differentiates A. galapagoenis from other Acantholichen species. Another characteristic of this taxon is that, when well developed, the thallus can get unusually large, occasionally covering bryophytes on tree trunks up to 1 m length. Additionally, in large specimens, the thallus center squamules often become necrotic. Because of the tiled, overlapping growth of the squamules,squamules in the thallus center regularly become shaded and are then unable to photosynthesize; these areas then lose the characteristic pigmentation of the photobiont and become beige. Squamules of other Acantholichen species are mostly broader and rarely grow overlapping each other, thus typically do not become necrotic. The species was first reported from the archipelago as Acantholichenpannarioides (Jørgensen 1998; Yánez et al. 2012), but the molecular data presented here and a thorough morphological and anatomical analysis of all material clearly indicates that all reports are based on one and the same species, which is endemic to the Galapagos. Throughout the archipelago no other lichen closely resembles A. galapagoensis (Bungartz et al. 2013).
This basidiolichen species is endemic to Galapagos. A recent species inventory found only five populations across four different islands. Natural habitats of Acantholichengalapagoensis are known from threatened tree ferns and shrub (Cyathea - endangered, Psychotria - vulnerable) and a vegetation type that is in many parts of Galapagos has deteriorated (Frullania-Zanthoxylon forests). Only on Santa Cruz thalli of the lichen have established on introduced Cinchona pubescens as an alternative habitat. Here, the practice of population reduction of Cinchona by chemical control needs to be carefully balanced against survival of refugium populations of Acantholichen.
Assessor/s: F. Bungartz; Reviewer/s: Scheidegger, C.; Contributor/s: Weerakoon, G.
Jørgensen, P.M. (1998) Acantholichen pannarioides, a new basidiolichen from South America. The Bryologist101(3): 444-447.
Dal-Forno, M., Lücking, R., Bungartz, F., Yánez-Ayabaca, A., Marcelli, M.P., Spielmann, A.A., Coca, L.F., Chaves, J.L., Aptroot, A., Sipman, H.J.M., Sikaroodi, M., Gillevet, P. & Lawrey, J.D. (2016) From one to six: Unrecognized species diversity in the genus Acantholichen (lichenized Basidiomycota: Hygrophoraceae). Mycologia108(1): 38-55.
Lawrey, J.D., Lücking, R., Sipman, H.J.M., Chaves, J.L., Redhead, S.A., Bungartz, F., Sikaroodi, M. & Gillevet, P.M. (2009) High concentration of basidiolichens in a single family of agaricoid mushrooms (Basidiomycota: Agaricales: Hygrophoraceae). Mycological Research113: 114-1171.
Lücking, R., Lawrey, J.D., Sikaroodi, M., Gillevet, P.M., Chaves, J.L., Sipman, H.J.M. & Bungartz, F. (2009) Do lichens domesticate photobionts like farmers domesticate crops? Evidence from a previously unrecognized lineage of filamentous cyanobacteria. American Journal of Botany96(8): 1409-1418.
Yánez-Ayabaca, A., Dal-Forno, M., Bungartz, F., Lücking, R. (2012) A first assessment of Galapagos basidiolichens. Fungal Diversity52: 225-244.
Special note from the Author of the assessment: Acknowledgments- Author thanks the Charles Darwin Foundation and the Galapagos National Park as well as a grant from the Mohamed Bin Zayed Species Conservation Fund (project 152510692) and the National Science Foundation (DEB 0841405), who all made this work on Acantholichen possible.
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