Oliver Gilbert was a pioneer, an outstanding field botanist and inspirational scientist. He worked in the broad fields of urban and lichen ecology and had almost 40 years of teaching and research experience within universities. Above all he was very approachable, an excellent teacher and fun to be with. Oliver was a leading figure in the British Lichen Society serving as BLS Bulletin Editor (1980–89 except 1987), President (1976–77) and was a frequent Council Member. He was elected an Honorary Member in 1997 and received the prestigious Ursula Duncan Award in January 2004. Oliver had an exceptional ability to find rare and interesting lichens and plant communities that others had overlooked and he constantly challenged conventional wisdom that particular habitats were uninteresting, especially urban habitats. His ecological ‘field craft’ skills were equally legendary. Passion for field work and British Lichen Society field meetings led him to organize a small grant awards scheme to stimulate others to attend field meetings and to submit their results for publication in the BLS Bulletin.

Xanthoparmelia isidiovagans and X. subverrucigera from Spain are described as new to science. Both species are characterized by an isidiate upper surface and the presence of the stictic acid chemosyndrome in the medulla, but X. isidiovagans has a vagrant thallus with markedly revolute lobes with a black lower surface, whereas X. subverrucigera has adnate thalli with subirregular lobes and a brown lower surface.

The first lichen-forming species of Psammina, P. palmata sp. nov., is described from decorticate oak in West Suffolk (UK). It is distinguished from other species by the palmate and 2–3-order branched non-septate conidia flattened in a single plane. The conidia recall those of the lichen-forming hyphomycete genus Cheiromycina in some respects, but do not originate from the swollen subglobose cells characteristic of that genus. The generic concepts in this complex of algicolous, lichen-forming, lichenicolous, and saprobic fungi are discussed, and it is concluded that Pycnopsammina should be treated as a synonym of Psammina as the conidiogenesis resembles that of the type species of Psammina, which also has rather similar conidiomata; the combination Psammina lobariae comb. nov. (syn. Pycnopsammina lobariae) is therefore made. A key to the eight species now accepted in the genus is provided, which now includes algicolous, lichen-forming, lichenicolous, and plant saprobic species.

Four new species and one new forma are described in the genus Porpidia. Porpidia flavocruenta Fryday & Buschbom, a member of the P. macrocarpa group that has previously been overlooked for ‘P. flavocoerulescens’, is reported from Austria, the British Isles, Scandinavia, Iceland, and North America (Alaska); P. islandica Fryday, Knoph & Hertel is reported from Iceland and Scotland; and P. pachythallina Fryday and P. striata Fryday from the British Isles only. The sorediate morph of P. superba is described as P. superba f. sorediata Fryday, known from the British Isles, Sweden, Svalbard, and North America (Maine). Variation in P. macrocarpa is discussed and the new combination P. macrocarpa f. nigrocruenta (Anzi) Fryday made. Secondary metabolite production is discussed and the variation in the production of chemosyndromes considered to be more variable than previously reported. The position of several other taxa is discussed and P. herteliana and P. musiva are reduced to synonymy with P. cinereoatra, P. calcarea to synonymy with P. superba, and P. diversa to synonymy with P. contraponenda. However, P. grisea and P. lowiana are provisionally maintained as distinct species from P. tuberculosa and P. cinereoatra respectively, although P. grisea has not been correctly recorded from the British Isles. The typification of Spiloma tuberculosa Sm., the basionym of Porpidia tuberculosa, is discussed and a lectotype proposed; the new combination Porpidia rugosa (Taylor) Coppins & Fryday is made and shown to be the correct name for P. glaucophaea; and Porpidia flavicunda (Ach.) Gowan is used for the esorediate taxon usually known as Porpidia flavocoerulescens because this epithet is to be proposed for rejection as it is considered to be of confused usage. Porpidia hydrophila is shown to be a member of the P. albocaerulescens group. Porpidia lowiana, P. nadvornikiana, and P. thomsonii are recorded for the first time from the British Isles, and P. macrocarpa f. nigrocruenta confirmed as a British taxon. Notes and a key are provided for all the species of the genus that have been reported from the area.

Lecania fructigena has been found in western Europe. This species, previously known only from western North America and north-western Mexico, is described and compared with related species. It is easily overlooked for L. aipospila. Lecania sampaiana is a synonym of L. aipospila.

Between 16–21 August 2004, 250 lichenologists gathered in Tartu, Estonia for the Fifth Symposium of the International Association for Lichenology (IAL5). The meeting comprised six principal lecture sessions and associated posters. This issue of The Lichenologist presents papers deriving from contributions to Session 3: Genes, Physiology and Structure. This session probably had the broadest scope of all those comprising the symposium because it essentially encompassed all aspects of the general biology of the lichen thallus. The response to this topic from prospective authors and presenters was excellent and the final programme included fourteen oral presentations and sixteen posters; of this total of thirty contributions, eight are published here. Inevitably, several of the oral and poster presentations were already submitted to, or destined for, alternative journals or were considered too preliminary to warrant publication at this stage. In particular, there were several excellent “molecular” contributions dealing with such topics as breeding systems, genetic diversity, microbial diversity within thalli, and the genetic control of secondary metabolite production, but none were available or offered as papers to this volume.

Micarea hypoviolascens sp. nov. (Pilocarpaceae) is described from an ancient woodland in western Scotland. It is the second species within Micarea known to have the olivaceous, K+ deep violet pigment (Sedifolia-grey) in the hypothecium.

The utility of plastic cover slips as a substratum for in situ study of lichen developmental stages is further explored in a neotropical foliicolous lichen community and in a European temperate corticolous community. Twenty-one months after placement in the tropical forest, the cover slips bore foliicolous lichen thalli with several species producing characteristic ascocarps and ascospores, indicating the suitability of the substratum for completion of the life cycle of these lichens. On cover slips placed within the temperate corticolous community, lichen propagules anchored to the substratum with relatively short attachment hyphae but did not develop further within the one year observation period. Intimately intermixed microbial communities of short-celled, mainly pigmented fungi and chlorophyte algae developed upon the transparent substratum. Among the algae, Trebouxia cells, often in groups showing cell division and without associated lichenizing hyphae, were commonly observed. The potential significance of the free-living populations in the life cycle of Trebouxia and in those of Trebouxia-associated lichen fungi is discussed.

Parmelia barrenoae is described as new to science in the P. sulcata complex on the basis of morphological and molecular data. The new species is superficially similar to P. sulcata but differs in having simple rhizines whereas the other species of the complex have squarrose rhizines. Nuclear ITS rDNA and partial β-tubulin gene sequences have been used as molecular markers. In the phylogenetic analysis, P. sulcata falls into four well supported clades, one of them corresponds to the morphotype that is described here as a new taxon. Six samples of the new taxon from different locations on the Iberian Peninsula form a strongly supported monophyletic group.

The following new species of Parmeliaceae are described from Rwanda: Hypotrachyna rwandensis Elix, Eb. Fischer & Killmann and Parmotrema afrocetratum Elix, Eb. Fischer & Killmann.

Lichen material from the Iberian Peninsula of Melanelia commixta, M. hepatizon and M. sorediella has been studied and compared on the basis of morphology, chemistry, habitat and distribution. The new combination Melanelia sorediella is proposed and Cetraria commixta f. sorediella is lectotypified. Chemotypes I and III have been detected in M. commixta. Melanelia sorediella is characterized mainly by the formation of pycnoisidia and soralia-like structures in the lamina and margins of the thallus and by the absence of pseudocyphellae and apothecia. The pycnoisidium is here described as a combination of isidia-like proliferations of the thallus surface containing pycnidia, carrying algae and acting as vegetative symbiotic propagules. Non detached pycnoisidia grow into lobuli in central parts of the thallus, regenerating it. Pycnoisidia, soralia-like areas and lobuli are formed as a consequence of pycnidia development. Melanelia sorediella is morphologically and chemically close to M. commixta and is currently known from mountains of central and south-west Europe where it grows on acid rocks. In south-western Europe, the meridional limit of the distribution of the three species studied seems to be located in the mountains of the central part of the Iberian Peninsula (Sistema Central Ibérico). Relevant data on the three species are provided and a key is also included.

The sorediate variety of Sclerophytomyces circumscriptus (Taylor) Sparrius & P. James (Roccellaceae, Arthoniales) is described from sheltered, acid rock along Europe's western coasts and the Atlantic islands. This sorediate taxon is reported from the British Isles, Ireland, France, Spain, Portugal, the Azores and the Canary Islands. A description of the morphology, distribution and ecology is provided. The phylogenetic position of the new taxon is discussed, as well as nomenclatural and orthographic issues. The name Sclerophytomyces is proposed as an orthographic correction of the published name Sclerophytonomyces.

The new lichenicolous hyphomycete, Monodictys epilepraria, is described from thalli of several Lepraria species. It is known from the Czech Republic, Great Britain, Lithuania, Poland, Spain and Sweden, and appears to be widespread, but probably much overlooked. The new species is characterized by relatively small, brown, muriform, smooth-walled conidia developing on decolourized patches of the host.

Pannaria isabellina is transferred from Psoroma to Pannaria as it lacks the amyloid apical ascus structure characteristic of Psoroma. However, it has an isolated position within Pannaria because of its lichenized squamules developing horizontally on a thin, filmy prothallus, and its thallus chemistry characterized by the norstictic acid chemosyndrome. It also has a sclerenchymatous epicortex and a characteristic perispore with gibbose wall swellings and long flagella-like apical extensions; both characters are not often found and are still insufficiently studied within the genus Pannaria. The gelatinous, long flagella-like apical extensions of the perispores probably serve to anchor the ascospores to thin and vertical substrata; the species seems to be concentrated in forest margins of evergreen forests along the coast of Chile, except in the Valdivian rainforest region where it extends further east.

Graphis tetralocularis C. Bock & Hauck is described as a new species from Rwanda. It is characterized by triseptate, hyaline ascospores 12–15(–17)×5–7·5 μm, a connivent, laterally carbonized exciple and by the presence of atranorin. So far, G. tetralocularis is only known from the type locality in central Africa, where it grows epiphytically on Nuxia floribunda in a dry forest.

The phylogenetic position of the European crustose pioneer lichen Moelleropsis (Biatora) humida (Kullhem) Coppins & P. M. Jørg. is studied using partial sequences of the mitochondrial SSU and nuclear LSU rDNA of 64 ascomycetes, including sequences of all known species of Arctomiaceae. The analysis places M. humida in the Arctomiaceae with strong support as sister to the Tasmanian genus Wawea. The genus Arctomia is monophyletic and sister-group to the Wawea+Moelleropsis humida clade. The new genus Gregorella is described to accommodate Moelleropsis humida and the new combination Gregorella humida (Kullhem) Lumbsch is proposed. The ontogeny of the ascomata of Gregorella humida is similar to that of other Arctomiaceae, in that the generative tissue is formed on a thallus outgrowth. The Arctomiaceae did not cluster with the bulk of cyanobacterial lichens in the Lecanorales suborder Peltigerineae (or Peltigerales), but is part of Ostropomycetidae. The closest relative of Arctomiaceae could not be identified, since the relationships of major clades within Ostropomycetidae lacked support.

In this study, the symbiont cells of several endolithic lichens colonizing granite in continental Antarctica and the relationships they have with the abiotic environment were analyzed in situ, in order to characterize the microecosystems integrating these lichens, from a microecological perspective. Mycobiont and photobiont cells, the majority classified as living by fluorescent vitality testing, were observed distributed through the fissures of the granite. The fact that extracellular polymeric substances were commonly observed close to these cells and the features of these compounds, suggest a certain protective role for these substances against the harsh environmental conditions. Different chemical, physical and biological relationships take place within the endolithic biofilms where the lichens are found, possibly affecting the survival and distribution of these organisms. The alteration of bedrock minerals and synthesis of biominerals in the proximity of these lichens give rise to different chemical microenvironments and suggest their participation in mineral nutrient cycling.

Strigula muscicola Berger, Coppins, Cl. Roux & Sérus. is described as new to science; it is a muscicolous species with aggregated ascomata and 3-septate ascospores, growing in subalpine habitats in Austria, Norway and Scotland.

The lichenicolous hyphomycete Taeniolella diederichiana Etayo & Calatayud, is described from the Andes (Colombia and Peru) and the Canary Islands. It grows on the thallus and apothecial margin of Placopsis. It is characterized by forming minute sporodochia over a basal group of polyhedral cells, and by its conidia with a verruculose to verrucose-striate wall.

A new species of pyrenocarpous lichen, Pyrenula subcylindrica, from the Sundarbans area on the delta of the River Ganges is described. It is characterized by ascomata with a distinct clypeus, and 7–11-septate ascospores 42–67 μm long made up of cells with rounded to polygonal lumina and with subacute apices.