This volume on lichen biodiversity and ecology is dedicated to Harrie Sipman. It contains 29 peer-reviewed contributions by 50 authors. The emphasis is on the biodiversity and ecology of lichens in the tropics, but some papers are devoted to related areas. This volume is indispensable for active lichenologists, especially because it contains keys to several lichen genera. Full monographs are presented for the reinstated genus Herpothallon (with 29 species), the new genera Diaphorographis (with 2 species), Sipmaniella (with 1 species) and Synarthothelium (with 2 species), and the genus Placopyrenium (with 14 species and 3 varieties). Keys are furthermore given to all cryptothalline species of Lecidea, the lichenicolous genus Sphaerellothecium and the species of Cryptothecia and Stirtonia in Thailand. The genus Trypetheliopsis is resurrected for Musaespora, and all relevant combinations are made. Most papers describe various new species from all over the world, in the genera Bacidia, Buellia, Caloplaca, Chapsa, Cladonia, Cryptothecia, Diaphorographis, Gassicurtia, Herpothallon, Micarea, Phaeographis, Placocarpus, Placopyrenium, Porina, Pyrenula, Pyxine, Stirtonia, Strigula, Synarthothelium, Thelocarpon, Thelopsis, Xanthoparmelia, and Zwackhiomyces. The newly described Thelopsis is intermediate between that genus and Topelia, leading to the supposition that these genera are one continuum and should be united. Floristic papers are presented on lichens from Montenegro, Korea, Japan, Thailand, Namibia (including the description of an association), South Africa and the Seychelles and bryophytes of the Galapagos, but specimens from a multitude of other countries ranging from Iceland to Australia are cited throughout the papers. The floristic papers contain also new synonymys and combinations, partly in additional genera like Mycomicrothelia. One paper is devoted to lichens and global warming. The volume also contains three phylogenetic studies, viz. on all lichen groups with cyanobacteria, on Schistophoron and on Tylophoron, in which a systematic placement for this enigmatic genus is postulated for the first time. The volume is completed by lists of published papers and species decribed by Harrie Sipman. The volume is richly illustrated and contains many colour photographs, e.g. from all Herpothallon species and from sections through the apothecia of many Lecidea species.