Acarospora rosulata in Europe, North America and Asia Kerry KNUDSEN, Valérie REEB, Martin WESTBERG, Rithu SRIKANTHA and Debashish BHATTACHARYA Abstract: Acarospora rosulata is revised and reported from North America and Mongolia. Acarospora bullata is not verified as occurring in South and North America and may be conspecific with A. rugulosa. Keywords: Acarosporaceae, ITS nrDNA, lichens, taxonomy Introduction Acarospora is a large and cosmopolitan genus erected by Massalongo (1852) that contains over 200 species and is not monophyletic (Reeb et al. 2004; Crewe et al. 2006). The type species of the genus is the yellow, terricolous Acarospora schleicheri (Ach.) A. Massal. The genus is characterized by polyspory (50 or more ascospores per ascus), simple hyaline ascospores, usually aspicilioid or pseudo-lecanorine apothecia, and bituni- cate but non-fissitunicate asci with a non- amyloid tholus (Knudsen 2007). Acarospora species are areolate to squamulose, brown or yellow, sometimes pruinose or effigurate, saxicolous or terricolous, incidentally and rarely lignicolous, with a small number of species lichenicolous with a parasitic juvenile phase (Magnusson 1929; Clauzade & Roux 1981; Knudsen 2007). Many species, including several yellow taxa, have a simple chemistry of gyrophoric acid usually with lecanoric acid (Knudsen 2007). This is best studied under the micro- scope with the application of KOH followed by C, to mounted thin sections which will produce a pinkish-red reaction. Rarely is thin-layer chromatography necessary, but some species such as Acarospora nicolai B. de Lesd. often have very low concentrations of gyrophoric and lecanoric acid (Knudsen & Morse 2009). Acarospora bullata Anzi is a brown species with a usually effigurate margin and contains gyrophoric acid. In our continuing studies of the genus Acarospora it became apparent that there were possible problems of hetero- geneity with Magnusson’s concept of A. bullata which included specimens from Asia, Europe and California (Magnusson 1929). It was also apparent that using an even broader concept of A. bullata that included South American specimens was unsatisfactory (Knudsen et al. 2008). Molecular phylo- genetic analysis to verify heterogeneity was therefore an appropriate tool in this case. We sequenced selected specimens identified as A. bullata from Asia, Europe, North and South America and used sequences of A. rugulosa Körb (Crewe et al. 2006) for phylo- genetic reconstruction and established these species as heterogenic. Acarospora rosulata (Th. Fr.) H. Magn. is an effigurate to non-effigurate brown species with gyrophoric acid known pre- viously only from a small area of Norway (Magnusson 1929). We discovered that specimens identified as A. bullata from K. Knudsen: Herbarium, Department of Botany and Plant Sciences, University of California, Riverside, California, 92591 USA kk999@msn.com V. Reeb, R. Srikantha and D. Bhattacharya: Depart- ment of Biology and Roy J. Carver Center for Compara- tive Genomics, University of Iowa, Iowa City, IA 52242, USA. M. Westberg: Cryptogamic Botany, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden. The Lichenologist 42(3): 291–296 (2010) © British Lichen Society, 2010 doi:10.1017/S0024282909990715