Background and aims – The corticolous microlichens are the greatest group of lichens in the world and also the least known. For this reason intensive studies on this group are seriously needed. Based on this necessity, the main objective of this paper is to present new records of corticolous microlichen species for South America, Brazil, the Southern region of Brazil and the state of Rio Grande do Sul. Methods – The species were collected in three different forest types: native Araucaria forest, Atlantic rainforest and riparian forests from the Pampa Biome. Key results – A total of 43 new records of corticolous microlichen species are here presented. Six species are new reports for South America: Cryptothelium cecidiogenum Aptroot & Lücking, Distopyrenis composita R.C.Harris, Graphis pseudocinerea Lücking & Umaña, Herpothallon echinatum Aptroot, Lücking & Will-Wolf, Lecanora thysanophora R.C.Harris and Psoroglaena stigonemoides (Orange) Henssen. Two species are new records for Brazil: Pyrenula dissimulans (Müll.Arg.) R.C.Harris and Rinodina conradii Körb., while four are new occurrences for the state of Rio Grande do Sul: Graphis elongata Zenker, Graphis furcata Fée, Graphis longula Kremp. and Haematomma africanum (Steiner) Dodge. Thirty-one new records are as well reported here for the Southern region of Brazil. Conclusion – The high number of new crustose species records of this study greatly contributes to the current knowledge on lichens. Additionally, our study highlights the importance of conserving all kinds of forest environments, since they are important areas for lichen establishment and dispersion.

ATLANTIC RAINFOREST; MICROLICHENS; NATIVE ARAUCARIA FOREST; PAMPA BIOME