The sexual reproduction structures are a mass of loose ascospores that are enclosed by a cup shaped exciple sitting on top of a tiny stalk, having the appearance of a dressmaker's pin (called a mazaedium), hence the common name pin lichen.[1]: 15 They are also commonly calledstubble lichens.[1]: 234
The genus was circumscribed in 1794 by the mycologist Christiaan Hendrik Persoon. He included three species in his initial circumscription of the genus: C. viride, C. salicinum, and C. pallidum.[3] The genus name, derived from the Latincalix or calicis ("cup") with the diminutive suffix -ium, refers to the shape of the ascocarps.[4]
The genus Calicium features crustose lichens, which can be verrucose to granular in texture, or immersed in the substrate, and display a range of colours from grey to green-grey, pale yellow, or dark green. Its photobiont, a symbiotic green alga, is of the trebouxioid type. The ascomata (fruiting bodies) are apothecial in nature, usually elevated on a long, distinct stalk with a spherical to lens-shaped head, though some may be directly attached (sessile). These stalks consist of thickened hyphae that are brown to greenish-black and irregularly interwoven. The cup-shaped excipulum, a supportive structure around the ascomata, is well developed and envelops the dry spore mass.[5]
The asci (spore-bearing cells) are cylindrical to clavate (club-shaped) and develop individually from ascogenous hyphae with croziers, typically dissolving early in their lifespan. Ascospores within the genus contain a single septum and form a distinctive black, dry-spore mass known as a mazaedium. These spores have a thick, dark brown wall, often adorned with unique ornamentation.[5] They are generally in the size range 7–19 by 4–8 μm.[6]
In terms of asexual reproduction, Calicium possesses pycnidia, which are sessile or slightly immersed structures producing conidia (asexual spores). These pycnidia are simple and spherical with a punctiform (point-like) ostiole. The conidiophores within are branched, with somewhat cylindrical, enteroblastic conidigenous cells. The conidia themselves are broadly ellipsoid to short-cylindrical, colourless, and lack septa.[5]
Calicium has a global presence, primarily found in cool to temperate regions, with only a few species known to occur in tropical areas. These species typically grow on bark and wood, with rare occurrences on rocks and one species specifically adapted to siliceous rocks. Calicium prefers environments with low light, high humidity, and shelter, often thriving in old-growth forests, although some species can adapt to more open, sun-exposed locations.[6]
The discovery of a Calicium-like fossil in Baltic amber dating back 55–35 million years ago myr indicates that the main distinguishing characteristics of this genus have persisted for at least tens of millions of years.[7] A fossil-calibrated phylogeny that includes this fossil suggests that the family Caliciaceae diversified from its most recent common ancestor 103–156 myr ago in the early Cretaceous.[8] This fossil lichen has since been formally named as Calicium succini.[9]
^Ulloa, Miguel; Aguirre-Acosta, Elvira (2020). Illustrated Generic Names of Fungi. APS press. p. 60. ISBN978-0-89054-618-5.
^ abcdGiavarini, V.J.; Purvis, O.W. (2009). "Calicium Pers. (1794)". In Smith, C.W.; Aptroot, A.; Coppins, B.J.; Fletcher, F.; Gilbert, O.L.; James, P.W.; Wolselely, P.A. (eds.). The Lichens of Great Britain and Ireland (2nd ed.). London: The Natural History Museum. p. 262. ISBN978-0-9540418-8-5.
^ abcdefghTibell, Leif (2006), "Calicium in the Indian Himalayas", Journal of the Hattori Botanical Laboratory, 100: 809–851, doi:10.18968/jhbl.100.0_809
^ abKettunen, Elina; Sadowski, Eva Maria; Seyfullah, Leyla J.; Dörfelt, Heinrich; Rikkinen, Jouko; Schmidt, Alexander R. (2019). "Caspary's fungi from Baltic amber: historic specimens and new evidence". Papers in Palaeontology. 5 (3): 365–389. doi:10.1002/spp2.1238.
^Persoon, C.H. (1797). Tentamen dispositionis methodicae Fungorum (in Latin). p. 59.
^Persoon, C.H. (1800). Icones et Descriptiones Fungorum Minus Cognitorum (in Latin). Vol. 2. pp. 27–60 [59, t. 14:6].
^ abBailey, F.M. (1891). "Contributions to the Queensland Flora". Botany Bulletin of the Department of Agriculture of Queensland. 7.
^Knudsen, K.; Kocourková, J.; Lendemer, J.C. (2019). "Calicium brachysporum, a rare California endemic". Bulletin of the California Lichen Society. 26 (2): 51–53.
^Nylander, W. (1860). Synopsis Methodica Lichenum Omnium hucusque Cognitorum, Praemissa Introductione Lingua Gallica (in Latin). Vol. 1. p. 153.
^Tibell, L. (2001). "A synopsis of crustose calicioid lichens and fungi from mainland Africa and Madagascar". Nordic Journal of Botany. 20 (6): 717–742. doi:10.1111/j.1756-1051.2000.tb00759.x.
^Murray, J. (1960). "Studies of New Zealand lichens. I - The Coniocarpinae". Transactions and Proceedings of the Royal Society of New Zealand. 88: 177–195.
^Tibell, L.; Thor, G. (2003). "Calicioid lichens and fungi of Japan". Journal of the Hattori Botanical Laboratory. 94: 205–260.
^Tibell, L. (1975). The Caliciales of boreal North America. Symbolae Botanicae Upsalienses. Vol. 21. p. 84.
^Tibell, L.; Frisch, A. (2010). "New data on crustose mazaediate lichens from tropical Africa". In Hafellner, J.; Kärnefelt, I.; Wirth, V. (eds.). Diversity and Ecology of Lichens in Polar and Mountain Ecosystems. Bibliotheca Lichenologica. Vol. 104. Stuttgart: J. Cramer in der Gebrüder Borntraeger Verlagsbuchhandlung. pp. 323–332. ISBN978-3-443-58083-4.
^Nylander, W. (1861). "Expositio Lichenum Novae Caledoniae". Annales des Sciences Naturelles. Botanique. 4 (in Latin). 15: 37–54.
^Williams, Cameron B.; Tibell, Leif (2008). "Calicium sequoiae, a new lichen species from north-western California, USA". The Lichenologist. 40 (3): 185–194. doi:10.1017/S0024282908007615.