- The Corticolous Crustose and Microfoliose Lichens of Northeastern Brazil – Diversity, Ecology, and Conservation (2006)
- Collections of crustose and microfoliose corticolous lichens made in a number of 22 localities of Atlantic rainforest, Caatinga and Brejos de Altitudes (caatinga enclaves) in the states of Rio Grande do Norte, Paraiba, Pernambuco, Alagoas, and Sergipe, in northeastern Brazil yielded a total of 450 species, distributed in 110 genera, in 32 families, 12 orders, and 4 classes of Ascomycota and one of Basidiomycota. A total of 14 taxa are described here as new to science in the genera Aciculopsora, Bacidina, Calopadia, Cryptothecia, Enterographa, Graphis, Malcolmiella, Phaeographis, and Plectocarpon. In addition, 5 new combinations are proposed in the genera Chapsa and 7 in the genera Malcolmiella. Identification keys to the genera and species of corticolous crustose and microfoliose lichens of northeastern Brazil are provided, with complete checklist and descriptions of new species. The comparison between different vegetation types and localities across the study area used the lichen species composition at each site to ordinate and classify sites. The highest dissimilarity was registered between the Atlantic rainforest sites, with an average of 21% and maximum of 55%. The lichen species composition from the Atlantic rainforest sites as a whole compared to the Caatinga sites showed dissimilarity values averaging 0.92 or 8% of shared species. The influence of tree bark characteristics and phorophyte species on lichen species composition, richness, and area cover, in a selected fragment of Atlantic rainforest was analyzed. Multivariate analysis of sample plots, including non-metric multidimensional scaling (NMS), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA), and also cluster analysis, indicated subtle patterns of phorophyte preferences among certain lichen species, as well as correlation with environmental parameters, in particular bark pH, degree of bark shedding, and density and size of bark lenticels. Individual and multiple correlation also revealed correlations between lichen species richness and area cover on one hand and bark pH (negative), density and size of bark lenticels (negative), degree of bark shedding (negative), presence of milk sap (positive), and diffuse site factor (positive). No distinct lichen communities were detected among the samples, but cluster analysis revealed three main sample groups and six subgroups with slightly different lichen species composition, each one with characteristic indicator species but with highly variable overall species composition. It is concluded that community formation in tropical rainforest understory lichens is governed by two main factors, phorophyte bark characteristics and microclimate, but is largely obscured by the stochastic effects of species dispersal and rare species, and also the amount of phorophyte tree diversity. It is predicted that phorophyte specificity is best observed in model systems with low tree and low lichen diversity, distinct differences between tree species in terms of bark characteristics, homogeneous population structure, and low microclimatic variation. Finally, three different sampling methods were considered on the present study and their efficiency for more accurate estimation of tropical microlichen diversity was tested. The analysis showed that opportunistic sampling fails to detect rare, inconspicuous, sterile, and/or cryptic species, usually neglected or overlooked in the field. It is also apparent that it is not the higher number of specimens collected via quantitative sampling that results in a higher number of species, but the method of selection of the specimens, which is subjective and biased towards abundant, conspicuous, fertile and/or distinctive species in opportunistic sampling, but objective and unbiased in quantitative sampling.