Ten parmelioid taxa in five genera were identified from Rarotonga, Cook Islands, South Pacific Ocean. These comprise: three species of Bulbothrix, one species of Canoparmelia, four species of Parmotrema, one species of Rimelia and one species of Xanthoparmelia. Canoparmelia rarotongensis Louwhoff & Elix is described as new, being distinguished from other species of this genus by its unique secondary chemistry (lecanoric acid) and conspicuous, inflated isidia. The majority of parmelioid lichens on Rarotonga have cosmopolitan and pantropical distributions. Bulboihrix is reported for the first time from the Polynesian region.

Trichothelium longisetum sp. nov. (Porinaceae) is described from a rainforest in northeastern Ecuador. It has a non-radiating photobiont, prominent, black perithecia, each with numerous, long-acute to acicular, black setae, and elongate-bacilliform, 9–15-septate ascospores. Remarkably, this lichen grows on wood rather than on the living leaves or bark of trees or shrubs. Four species of Porina are also reported for the first time from Ecuador.

The taxonomy of the foliicolous members of Arthoniaceae (Anhonia, Arthothelium, Cryptothecia, Eremothecella) in Costa Rica is revised. Cryptothecia farkasiae sp. nov. is described, being closely related to Stirtonia sprucei, and bearing pycnidia reminiscent of Eremothecella. Anhonia lividofusca is placed in synonymy with A. aciniformis. Pycnidia and pycnospores are further described for Anhonialeptosperma, A. cyanea, A. palmulacea, A. trilocularis, Anhothelium cingulatum, Stinonia sprucei and S. macrocephala, and campylidia were found on thalli of Anhonia aciniformis. Anhonia nigratula and Cryptothecia Candida are reported for the first time from Costa Rica, and new localities are given for previously reported species. Ecological data are provided, and the relationships between foliicolous members of the Arthoniaceae are discussed.

Three new maritime saxicolous Ramalina species are described from Australia, R. litorea, R. whinrayii and R. caespitella N. Stevens spp. nov. The first species is tropical in occurrence, whereas the last two are temperate taxa and endemic to Australia.

Nimisia fuegiae Kärnef. & Thell gen. et sp. nov. is described from Argentinian Tierra del Fuego. The new lichen differs from possibly related groups within the Parmeliaceae in unique anatomical characters, i.e. a medullary layer composed of extremely thick and strongly gelatinized periclinally arranged hyphae and a lower cortex composed of only a few layers of strongly pigmented, rather large cells. Ascus characters support its position in the Parmeliaceae. The new genus, which is named in the honour of its first discoverer, is discussed in relation to several other well-investigated members of the family.

The stages of vegetation development close to two glacier fronts on two of the South Shetland Islands (Livingston and Robert) within the Maritime Antarctic were studied with special reference to saxicolous lichens. A lichenometric study of the crustose lichen Caloplaca sublobulata was carried out at both sites. On the moraine of Livingston Island, rock size played an important role in lichen development, explaining most of the differences observed in the diameter of C. sublobulata, the number of species, and the percentage of cover among the rocks studied. On Robert Island, the distance from the glacier front was associated with the lichen cover of the rocks but not with diameter of C. sublobulata This homogeneous distribution of C. sublobulata thallus size on the Robert Island study area points to a simultaneous recolonization of the whole zone by this lichen. The lichen development in the area studied on Robert Island seems to have been drastically affected by fluctuations in the persistence of snow cover following glacier front retreat. Tentative associations between ice retreat and colonization, on the o e hand, and changes in snow cover duration and the dynamic processes of extinction and recolonization, on the other, are suggested from comparison of the two zones.

Three species of Porina (Trichotheliaceae), P.kansriae P. M. McCarthy, P. siamensis P. M. McCarthy and P. wolseleyae P. M. McCarthy, are described from aquatic and semi-aquatic rocks in montane rainforest in north-eastern Thailand.

The genus Lecidea in the lichen flora of the gypsum soils of Spainis represented b two species: L. gypsicola Llimona and L. circinarioides Casares & Hafellner sp. nov., which are described in this article. Chemical, anatomical and ecological differences are also described, as is the taxonomic value of the morphological characteristics of the mature ascoma.

Skomer Island, a National Nature Reserve, lies off the West coast of Wales. This small island holds lichen communities of international importance associated with large populations of seabirds. Saxicolous lichen communities are described, 248 species listed and details given of a base-line monitoring programme, which will provide data on changes in the lichen flora over time and distinguish cyclical from permanent deleterious changes. Threats to island populations are discussed, such as the likely effects of oil pollution following the Sea Empress accident in February 1996.

The spatial distribution of corticolous lichens was studied along Big Seven Mile Creek (Cabell County, West Virginia, U.S.A.), a small stream that was periodically inundated by floodwaters carrying heavy loads of sediment. Lichen communities located at 0, 1.0 and 1.5 km from the confluence with the Ohio River were compared using step-wise discriminant analysis, a multivariate technique. Of the physical factors tested, the results indicated that the sediment on the tree boles was the most important factor separating the three stations and bole heights. Species richness was established to be an important mensurational variable separating stations, bole heights, and parallel and perpendicular transects. Changes observed in lichen community structure are assumed to have resulted from microclimatic variation brought about primarily by sedimentation associated with flooding. Failure of the physical factors and biotic variables to separate tree bole aspects (faces of boles in respect to the stream) indicate that abrasion and current-induced exfoliation are not important factors affecting lichen communities in the study area. Corticolous lichens occurring along streams subject to periodic inundation may represent a useful indicator in studies of flooding, water quality, and/or sedimentation in watersheds.

Pertusaria etayoi, found on lava flows and basaltic rocks from the Canary Islands, is described as new to science. It is the only species in the group of saxicolous Pertusaria with verruciform apothecia and 2 rough-walled ascospores to contain thiophaninic acid. A description of the species is given together with notes on its chemistry, distribution, ecology and taxonomy. Possible related lichen taxa are discussed briefly.