The extensive coastal, montane and woodland habitats on Thásos presumably support a rich and interesting lichen flora, but it is difficult to find any information on this group of plants for Thásos. For instance, there are no records for Thásos in Rechinger, K.H. (1943) Flora Aegea. Flora der Inseln und Halbinseln des Ägäischen Meeres. Akad. Wiss. Wein, Math.-Naturwiss. Kl., Denkschr., 105 (1). The only scientific paper to deal substantially with lichens on Thásos is a brief study by Popnikolov (1956), which lists 27 taxa recorded from the vicinity of Thassos Town in the 1940s and I am most grateful to Andrey Kovatchev for providing a copy of this reference. Other than this, Geisller (1977) reports six species from the island, including several from Ipsarion.
The herbarium of the Dept. of Botany at the University of Essen, Germany, contains an example of the beard lichen Evernia prunastri (L.) Ach. collected from the slopes of Profitis Ilias in 1994. I have collected a specimen of the lungwort Lobaria pulmonaria (L.) Hoffm. [det. R.G. Woods] from ancient plane trees in the hills above Thassos Town, alongside a tributary of the main river which runs past Ag. Marina. Lungworts are species of clean, moist air and may be indicative of the presence of other important epiphytic lichen species in this beautiful fragment of deciduous woodland.
Until recently this amounted to the sum of our knowledge on the lichen flora of Thásos, but further records have come to light in the course of B.F.M. Abbott's dedicated research whilst compiling a checklist of the lichens of Greece (Abbot 2009). A significant addition comes from the nineteen species recorded by I. Piút during a visit to the island in August 2007 and two additions to the island checklist come from specimens in the herbarium of M.R.D. Seaward.
In total, Abbott (2009) lists 47 taxa from Thásos, though he notes that Popnikolov's record of Flavocetraria nivalis is almost certainly erroneous as this is an arctic-alpine species not recorded elsewhere in Greece. In 2010 Sipman & Ahti (2011) collected specimens of Cladonia from the edge of the pine forest above Maries and reported seven species new to Greece, including one, C. graeca, new to science. Along with the record of Lobaria pulmonaria mentioned above, this means that 54 taxa have been reliably recorded from the island. Considering the degree of attention paid to lichens in Greece generally, including the islands, this is a reasonable tally. However, over 1300 Greek taxa are documented by Abbott and some of the larger islands have over 200 taxa recorded so there are likely to be many more species awaiting discovery on Thásos, as Sipman & Ahti have shown.
I'm indebted to Bernard Abbott for his kindness in allowing me to consult his remarkable checklist. The records are displayed as an annually updated .pdf file, which is downloadable from the Lichens of Greece website. This site also includes a detailed and comprehensive key to all of the lichen species known from Greece, incorporating taxa from neighbouring areas that may be expected to occur in Greece. This is also freely available in .pdf format from http://lichensofgreece.com/flora.pdf.
Aspicilia calcarea (L.) Mudd var. calcarea Walter (1976)
Bryoria implexa (Hoffm.) Brodo & D. Hawksw.
Caloplaca flavescens (Huds.) J. R. Laundon
Caloplaca inconnexa (Nyl.) Zahlbr. var. inconnexa
Caloplaca pollinii (A. Massal.) Jatta
Caloplaca saxicola (Hoffm.) Nordin
Cladonia convoluta (Lam.) Anders
Cladonia crispata (Ach.) Flot. var. cetrariiformis (Delise) Vain.
Cladonia diversa Asperges (nom. inval.)
Cladonia floerkeana (Fr.) Flörke
Cladonia foliacea (Huds.) Willd.
Cladonia furcata (Huds.) Schrad.
Cladonia graeca Sipman & Ahti
Cladonia parasitica (Hoffm.) Hoffm.
Cladonia pyxidata (L.) Hoffm.
Cladonia rangiformis Hoffm.
Cladonia squamosa Hoffm.
Cladonia uncialis (L.) F.H. Wigg. ssp. biuncialis (Hoffm.) M. Choisy
Collema cristatum (L.) F. H. Wigg.
Collema nigrescens (Huds.) DC.
Collema polycarpon subsp. corcyrense (Arnold) Pisút
Diploschistes muscorum (Scop.) R. Sant.
Diploschistes ocellatus (Vill.) Norman
Evernia prunastri (L.) Ach.
[Flavocetraria nivalis (L.) Kärnefelt & A. Thell - presumed incorrect]
Hypogymnia physodes (L.) Nyl.
Hypogymnia tubulosa (Schaer.) Hav.
Lecanora dispersa (Pers.) Sommerf.
Lecanora rupicola subsp. sulphurata (Ach.) Leuckert & Poelt
Leprocaulon microscopicum (Vill.) Gams ex D. Hawksw.
Leptogium lichenoides (L.) Zahlbr. var. lichenoides
Lobaria pulmonaria (L.) Hoffm.
Lobothallia radiosa (Hoffm.) Hafellner
Neofuscelia pulla (Ach.) Essl.
Ochrolechia androgyna (Hoffm.) Arnold
Ochrolechia parella (L.) A. Massal.
Parmelina tiliacea (Hoffm.) Hale
Pertusaria albescens (Huds.) M. Choisy & Werner var. albescens
Pertusaria amarescens Nyl.
Pertusaria flavida (DC.) J. R. Laundon
Pertusaria hymenea (Ach.) Schaer.
Pertusaria pertusa (Weigel) Tuck.
Physconia distorta (With.) J. R. Laundon
Platismatia glauca (L.) W. L. Culb. & C. F. Culb.
Protoblastenia rupestris (Scop.) J. Steiner
Pseudevernia furfuracea (L.) Zopf var. furfuracea
Pseudevernia furfuracea var. ceratea (Ach.) D. Hawksw.
Ramalina elegans (Bagl. & Car.) Stizenb.
Ramalina farinacea (L.) Ach.
Ramalina subfarinacea (Nyl. ex Cromb.) Nyl.
Solenopsora candicans (Dicks.) J. Steiner
Toninia sedifolia (Scop.) Timdal
Verrucaria calciseda DC.
Verrucaria nigrescens Pers.
Xanthoparmelia conspersa (Ach.) Hale
Saxicolous lichens - Ipsarion summit (Oct 2001)
Abbott, B.F.M. 2009. Checklist of the lichens and lichenicolous fungi of Greece. Bibliotheca Lichenologica 103:1-368
Geissler, P. 1977. Zur Moos- und Flechtenflora Nordgriechenlands. Bauhinia 6 (1):189-213
Linda in Arcadia. 2013. Atlas of Greek lichens (and lichenicolous fungi). Privately produced.
Popnikolov, A. 1956. Flechten von Ost - (Griechisch) Mazedonien. Bull. de L'Institut Botanique, Academie Bulgare des Sciences, 4: 353-356. [in Bulgarian]
Sipman, H.J.M. & Ahti, T. 2011. Contribution to the Cladonia mycota of Greece, including Cladonia graeca sp. nov. Mycosystema, 30(6): 877-880