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The new lichenicolous fungusCapronia suijaegrowing on the thallus of corticolousXanthoria parietinais described from Belarus and compared with similar species. In addition to its host selection, the species is characterized by comparatively small ascomata, 40–80 μm diam., and (0–1–)3-septate ascospores, 9·5–11·5×4·0–5·0 μm. A key to the lichenicolous fungi growing onXanthorias. str. is provided.

The green algal photobionts of 12 Xanthoria, seven Xanthomendoza, two Teloschistes species and Josefpoeltia parva (all Teloschistaceae) were analyzed. Xanthoria parietina was sampled on four continents. More than 300 photobiont isolates were brought into sterile culture. The nuclear ribosomal internal transcribed spacer region (nrITS; 101 sequences) and the large subunit of the RuBiSco gene (rbcL; 54 sequences) of either whole lichen DNA or photobiont isolates were phylogenetically analyzed. ITS and rbcL phylogenies were congruent, although some subclades had low bootstrap support. Trebouxia arboricola,T. decolorans and closely related, unnamed Trebouxia species, all belonging to clade A, were found as photobionts of Xanthoria species. Xanthomendoza species associated with either T. decolorans (clade A), T. impressa, T. gelatinosa (clade I) or with an unnamed Trebouxia species. Trebouxia gelatinosa genotypes (clade I) were the photobionts of Teloschistes chrysophthalmus,T. hosseusianus and Josefpoeltia parva. Only weak correlations between distribution patterns of algal genotypes and environmental conditions or geographical location were observed.

Three new Xanthoria species are described from South Africa. Xanthoria hirsuta sp. nov. has hairs on the surface of the thallus and apothecia, best visible in young, growing parts. Dust particles and sand granules stick to this hairy surface, giving the thallus a somewhat dirty appearance. Xanthoria inflata sp. nov. has inflated lobes similar to a Menegazzia. It carries numerous crystals on its medullary hyphae, which are ivory-coloured in young, but intensely orange coloured in old lobes. Xanthoria doidgeae sp. nov. has relatively small lobes with pruinose margins. All three species are fertile, none of them forms symbiotic propagules.

Specimens of Xanthoria parietina were collected from worldwide locations and ascospore discharge used to establish axenic cultures of the mycobiont. DNA was extracted and RAPD-PCR fingerprinting of 59 isolates was successfully achieved, resulting in 58 unique fingerprints. 110 multilocus RAPD markers were generated and used to construct a dendrogram. Two main groups were distinguished (75% bootstrap support): the first comprising samples from the Iberian Peninsula, the Balearic and Canary Islands; the second comprising all other worldwide samples including isolates from throughout Europe and North America. Samples from Australia and New Zealand clustered with the second group except one additional, phenotypically distinct specimen, not belonging to X. parietina, which formed an outgroup. However, comparative DNA sequence analyses are required to verify this interpretation.

Two new species, Xanthoria karrooensis S. Kondratyuk & Kärnefelt and Xanthoria alexanderbaai S. Kondratyuk & Kärnefelt, both apparently endemic to South Africa, are described and illustrated. Other xanthorioid species known from southern Africa are listed in a Table and a preliminary key is provided for the African species. The new species are compared with a number of presumably related species, and a Table is provided comparing the character states for the new species and related species.

Xanthoria poeltii, a new species combining characters of X. candelaria and X. ulophyllodes from Sweden, Denmark, Germany and Hungary, is described and illustrated. Comments about its differences from related taxa are provided.

Two new species of Xanthoria are described and illustrated, and comments about their differences from related taxa are provided. These are: X. ascendens from bark and shrub remains in sea-shore sand dunes and hillsides in Argentina, Chile and Peru, and X. ucrainica, from bark, stones, and some man-made substrata in the Ukraine, Sweden, United Kingdom, Germany, Austria and Asian Russia.

Xanthona parietina thalli were collected from a ‘clean-air’ location and from a polluted area. Ramalina duriaei thalli were collected from the same ‘clean-air’ location and some thalli were transplanted to air polluted locations, where R. duriaei no longer occurs. The effects of air contaminants on these two lichens were compared under controlled laboratory conditions and in field experiments. Air contaminants and exposure to bisulphite ions had little or no damaging effect on X. parietina, whereas severe damage was caused to R. duriaei, as judged by chlorophyll degradation, autofluorescence of photobionts, photosynthetic activity, membrane integrity and ATP content. The different responses presented confirm the sensitivity of R. duriaei and resistance of X. parietina to air pollution.

Thirteen isidiate taxa in the Teloschistales are briefly discussed, i.e. Letrouitia corallina (Müll. Arg.) Hafellner, L. leprolyta (Nyl.) Hafellner, Caloplaca bassiae (Ach.) Zahlbr., C. granulosa (Müll. Arg.) Jatta, C. herbidella (Hue) H. Magn., C. isidiigera Vězda, C. isidiosa (Vainio) Zahlbr., C. littorea Tavares, C. namibensis Kärnef., C. ochraceofulva (Müll. Arg.) Jatta, C. verruculifera (Vainio) Zahlbr., Xanthoria domogledensis Veˇzda and X. isidioidea (Beltr.) Szat. The presumed origins and affinities of these taxa, which are also often fertile, are discussed. The role of isidia in reproduction and dispersal, and the justification of specific status in some of these taxa is questioned.

Lecanora demissa (Körb.) Zahlbr. is a crustose, lobate lichen that produces soredia and conidiomata but no apothecia. Its placement in Lecanora has long been questioned but nothing better has been proposed. We have studied the nuclear rDNA of the ITS regions and the SSU of L. demissa. In an alignment of the ITS regions of several representatives of Lecanora s. lat. it could clearly be shown by a PAUP analysis, using Aspicilia caesiocinerea as outgroup, that L. demissa does not belong to Lecanora. In a PAUP analysis of sequences of the SSU from representatives of the order Lecanorales, using members of Saccharomycetales as outgroup, L. demissa clustered on a well-supported branch with Caloplaca chlorina. In a further analysis of the ITS sequences of L. demissa together with representatives of Caloplaca and Xanthoria using Protoparmelia as outgroup two most parsimonious trees were found. In these trees the L. demissa branch was well within a strongly supported clade with C. cerina, the type species of the genus Caloplaca. The sister taxon to L. demissa in this analysis was C. variabilis. Chemical data and characters of the conidiomata support the affinity with Caloplaca and the new combination C. demissa (Körb.) Arup & Grube is therefore proposed. A lectotype for Imbricaria demissa has been designated. The phylogenetic analysis of several representatives of the genera Caloplaca and Xanthoria suggests that these genera are not monophyletic as presently circumscribed. Two large, monophyletic groups of species could be recognized, one with Xanthoria species mixed with lobate and crustose members of Caloplaca, and one with mainly crustose Caloplaca, including both species with orange or black apothecia.

Two corticolous species of the lichen genus Xanthoria, X. alfredi S. Kondratyuk & Poelt from Russian and Chinese Far East and X. aphrodites Kalb, Poelt & S. Kondratyuk from Cyprus are described. Morphological characters, in particular the presence of true rhizines within Xanthoria and their diVerences from hapters are indicated. Xanthoria novozelandica Hillmann is the first species of Xanthoria in which oil paraphyses have been found. A key to the treated species, including X. novozelandica and Xanthoria sp. from western North America is provided. The ecology and distribution of described species are discussed. Xanthoria alfredi and X. ulophyllodes probably constitute a typical species pair; X. alfredi and X. aphrodites are relict endemics. ? 1997 The British Lichen Society