The aim of the present study was to identify food sources of bark-living oribatid mites to investigate if trophic niche differentiation contributes to the diversity of bark living Oribatida. We measured the natural variation in stable isotope ratios ((15)N/(14)N, (13)C/(12)C) in oribatid mites from the bark of oak (Quercus robur), beech (Fagus sylvatica), spruce (Picea abies) and pine (Pinus sylvestris) trees and their potential food sources, i.e., the covering vegetation of the bark (bryophytes, lichens, algae, fungi). As a baseline for calibration the stable isotope signatures of the bark of the four tree species were measured and set to zero. Oribatid mite stable isotope ratios spanned over a range of about 13 delta units for (15)N and about 7 delta units for (13)C suggesting that they span over about three trophic levels. Different stable isotope signatures indicate that bark living oribatid mites feed on different food sources, i.e., occupy distinct trophic niches. After calibration stable isotope signatures of respective oribatid mite species of the four tree species were similar indicating close association of oribatid mites with the corticolous cover as food source. Overall, the results support the hypothesis that trophic niche differentiation of bark living oribatid mites contributes to the high diversity of the group.

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The genus Melanelia was segregated from Parmelia s. l. by Esslinger (1978). A taxonomic treatment of the whole group and first distribution maps of many species were given by Esslinger (1977). Ahti (1966) dealt in-depth with the ecology and distribution of the non-sorediate and non-isidiate holarctic species. Thell (1995) combined some species formerly belonging to Cetraria to Melanelia.Recent studies considering molecular, chemical and morphological characters of 15 of the 40 Melanelia species have led to the conclusion that the genus is not monophyletic (Blanco et al., 2004), and two new genera have been proposed, circumscribing probably monophyletic groups: Melanelixia O. Blanco et al. contains eight species; M. fuliginosa, M. glabra, M. subargentifera and M. subaurifera occur in Europe. Melanohalea O. Blanco et al. contains 19 species; M. elegantula, M. exasperata, M. exasperatula, M. infumata, M. laciniatula, M. olivacea, M. septentrionalis and M. subolivacea occur in Europe and Macaronesia. According to this study, Melanelia stygia, as the type species of the genus Melanelia, has to be placed outside the parmelioid lichens, and M. disjuncta forms a further group, possibly related to some Neofuscelia species, a genus that is now placed in Xanthoparmelia. Furthermore, ABSTRACT Aim The global distribution of the European species of Melanelia Essl. (Lichenes: Parmeliaceae) was investigated in order to understand their distribution patterns against the background of ecogeographical and historical factors.Location The location of the study is global, with a local emphasis on Europe.Methods Geographical distribution and ecology of the species were investigated on the basis of herbarium studies and data from the literature as well as field observations. Distribution maps were created with ArcView GIS. The distribution patterns are expressed as three-dimensional 'areal formulas', regarding zonal distribution, altitudinal range and oceanicity, using a previously described method. The observed distribution patterns are discussed on the basis of their analogies with vascular plants and with respect to the ecogeographical vs. historical factors reflected by them. ResultsWith the exception of one species that is endemic to Europe, all species studied occur in both northern continents. A number of species have tropicalalpine outposts, and two species occur also in extratropical zones of the southern hemisphere. Arctic and boreal distributions are circumpolar, while in the southern holarctic zones an affinity to the western sides of both northern continents is frequent. Main conclusionsThe distribution patterns appear to be mainly determined by contemporary ecogeographical factors. Most species probably have largely filled their potential distribution, at least within the Holarctic. Thus, the geographical origin and dispersal history of a species cannot reliably be reconstructed; they can be dissimilar in different species with similar distributions.

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Aim The (world) distribution of the European species of Physconia Poelt (Lichenes: Physciaceae) [except Ph. distorta (With.) J. R. Laundon and Ph. americana Essl.] was investigated. The study was complemented by data on the ecological behaviour of the species.Location The location of the study is the whole world with a local emphasis on Europe.Methods The geographical distribution of the lichen species under consideration was investigated from collection data of herbaria and field studies in a databank. Additional data were taken from existing literature and critically considered. Distribution maps were created with ArcView GIS. The distribution patterns are expressed as threedimensional areal formulas, regarding zonal distribution, altitudinal range and oceanity of the species distributions, using the method of Meusel et al. (1965). ResultsThe distribution patterns of the ten Physconia taxa considered are represented in detailed maps and expressed as three-dimensional areal formulas. The ecological behaviour was discussed. Physconia muscigena and Ph. perisidiosa are species of bipolar distribution type, the other species are holarctic types. Physconia detersa and Ph. enteroxantha occur in both Eurasia and North America, the remaining species (Ph. grisea ssp. grisea, Ph. grisea ssp. lilacina, Ph. petraea, Ph. servitii, Ph. subpulverulenta and Ph. venusta) are pure Old world taxa with a much more limited distribution.The majority of the European Physconia taxa are distributed meridionally to submeridionally and occur preferentially in suboceanic areas.Main conclusions Some of the species under consideration have a wide distribution, nevertheless they show clear affinities to ecological conditions that influence their distribution patterns. A number of species show not only zonal and regional restrictions, but also affinities to the western climatic type. The Mediterranean is the centre of diversity of the genus Physconia in Europe.