Floristic, vegetational and ecological features of lichens in ultramafic environments are reviewed using a wide range of literature dating from the beginning of the 20th century. Co-presence of acidophytic (silicicolous) and basiphytic (calcicolous) species and the occurrence of species characterized by particular (disjunct) distribution patterns are features of lichens in ultramafic environments. It is not possible to detect consistent trends in data on other broadly accepted features, such as paucity of species, low cover and the occurrence of particular ecotypes because of the influence of several environmental factors in addition to the substratum. Some recent data about physico-chemical interactions between saxicolous lichens and ultramafic rocks are also reported.

Similarly to other Mediterranean regions, Italy is expected to experience dramatic climatic changes in the coming decades. Do to their poikilohydric nature, lichens are among the most sensitive organisms to climate change and species requiring temperate-humid conditions may rapidly decline in Italy, such in the case of the epiphytic Lobaria species that are confined to humid forests. Our study, based on ecological niche modelling of occurrence data of three Lobaria species, revealed that in the next decades climate change will impact their distribution range across Italy, predicting a steep gradient of increasing range loss across time slices. Lobaria species are therefore facing a high extinction risk associated with reduction of their range. The current patterns indicate that only L. pulmonaria still has a continuous distribution across Italy, with potential contact between Apennine and Alpine populations. This situation is consistent with the wider climatic niche of this species, still offering a major opportunity for its successful long-term conservation. Results (a) support the inclusion of the three Lobaria species in European conservation policies, such as the Habitat Directive, and (b) warn against an over-estimation of the indicator power of single flagship species to establish conservation priorities for lichens, indicating that even lichens with peculiar and similar climatic envelopes may fail to co-occur within a given forest stand. A multiple indicator approach could provide more useful tools for a community-based conservation strategy for epiphytes.

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Summary1. We attempted to elucidate the roles of b-diversity components and similarity in shaping Lobaria pulmonaria lichen communities in Italian forests to provide scientific tools for improving their longterm conservation. 2. A total of 20 sites were selected by stratified random sampling, including five chestnut forests, seven beech-silver fir forests and eight oak forests distributed across 10 administrative regions of Italy. Site selection was based on a national data base including all the available records of L. pulmonaria in Italy. In each forest, four plots were randomly placed, and in each plot, 5-6 trees were randomly selected for lichen sampling. For each forest and plot, meaningful predictors of lichen patterns were quantified. In particular, factors indicative of both geographic conditions and forests structure were considered. The SDR simplex approach was used to estimate the relative importance of similarity (S), relative species replacement (R) and relative richness difference (D) to b-diversity and similarity, while a hierarchical partitioning (HP) method was used to evaluate the relative importance of environmental predictors in explaining their patterns. 3. A total of 201 lichens and three nonlichenized fungi were found, including 51 species of conservation concern. The components of b-diversity and similarity contributed to shaping L. pulmonaria communities at both forest and plot scales across Italy, resulting in nearly random compositions, that is, the species set on each tree was a random sample from the available species pool. Species replacement and similarity were generally associated with forest structure predictors, while richness difference was mainly associated with geographic predictors. The implication of this is that the long-term conservation of L. pulmonaria communities could be promoted by maintaining scattered nodes and appropriate habitat traits, especially in large forested landscapes where species turnover is higher. 4. Synthesis. In this work, we used a new approach for analysing a countrywide data set improving the ecological understanding of the dynamics regulating epiphytic communities. In particular, this study improves the understanding of the contribution of different components of diversity across two spatial scales and evaluates the relative importance of environmental predictors in explaining variation of each diversity component.

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