Abstract
A total of 233 foliicolous lichen species and 18 lichenicolous fungi are reported from Guyana as a result of the Smithsonian „International Cryptogamic Expedition to Guyana“ 1996. Three lichens and two lichenicolous fungi are new to science: Arthonia grubei sp.n., Badimia subelegans sp.n., Calopadia pauciseptata sp.n., Opegrapha matzeri sp.n. (lichenicolous on Amazonomyces sprucei), and Pyrenidium santessonii sp.n. (lichenicolous on Bacidia psychotriae). The new combination Strigula janeirensis (Bas.: Phylloporina janeirensis; syn.: Raciborskiella janeirensis) is proposed. Apart from Amazonomyces sprucei and Bacidia psychotriae, Arthonia lecythidicola (with the lichenicolous A. pseudopegraphina) and Byssolecania deplanata (with the lichenicolous Opegrapha cf. kalbii) are reported as new hosts for lichenicolous fungi. Arthonia pseudopegraphina growing on A. lecythidicola is the first known case of adelphoparasitism at generic level in foliicolous Arthonia. Arthonia flavoverrucosa, Badimia polillensis, and Byssoloma vezdanum are new records for the Neotropics, and 115 species are new for Guyana, resulting in a total of c. 280 genuine foliicolous species reported for that country, while Porina applanata and P. verruculosa are excluded from its flora. The foliicolous lichen flora of Guyana is representative for the Guianas (Guyana, Suriname, French Guiana) and has great affinities with the Amazon region, while the degree of endemism is low. A characteristic species for this area is Amazonomyces sprucei. Species composition is typical of Neotropical lowland to submontane humid forests, with a dominance of the genera Porina, Strigula, and Mazosia. The table mountain vegetation supports elements of the upper montane forest, such as Echinoplaca fusconitida and Logilvia gilva. Foliicolous lichen diversity is highest in undisturbed lowland to submontane humid forest, much lower in the table mountain vegetation and drastically decreased in semi-open secondary vegetation and the coastal savanna. Species composition in semi-open, disturbed vegetation is similar to that found in the undisturbed forest canopy. Site preferences of foliicolous lichens follow those established by studies in other Neotropical regions like Costa Rica.