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Three species of Graphis (Graphidaceae) are described from Mexico from two research stations of the Universidad Nacional Autónoma de México (UNAM): Chamela Biological Station in the Cuixmala-Chamela Biosphere Reserve, Jalisco, and Los Tuxtlas Tropical Biological Station in the Los Tuxtlas Biosphere Reserve, Veracruz. The new species Graphis bungartzii Barcenas-Peña, Lücking, Herrera-Campos & R. Miranda is characterized by erumpent lirellae with a lateral thalline margin, striate labia and laterally carbonized exciple, transversely septate ascospores, and norstictic and connorstictic acids. Graphis chamelensis Barcenas-Peña & Lücking has prominent lirellae with a basal to lateral thalline margin, entire labia and completely carbonized exciple, transversely septate ascospores, and norstictic acid. Finally, Graphis rosae-emiliae Barcenas-Peña & Lücking is characterized by erumpent lirellae with lateral thalline margin, striate labia and completely carbonized exciple, transversely septate ascospores, and no substances detected by TLC. We present updates to the world key to Graphis for 41 newly described or reinstated species since the world key was published in 2009. The following new combination is proposed: Pallidogramme parvicarpum (B. O. Sharma & Khadilkar) Lücking comb. nov., based on Graphis parvicarpa B. O. Sharma & Khadilkar.

An inventory of foliicolous lichens in Mexican lowland and montane rainforest revealed a total of 288 species, 238 of which are new records for the country, raising the number of reported lichen species to c. 1800. Among the new records, there are 29 recently described species and four new records for the Neotropics and the Americas, while five taxa are for the first time reported for Central America. The 293 species now known from Mexico comprise nearly two-thirds pantropical to cosmopolitan or intercontinentally distributed taxa, whereas little more than one-third are Neotropical or American, and only 6% are potentially endemic to the country. A comparison with other lowland and montane rainforest sites in Guatemala, Costa Rica and Ecuador shows that on average lowland sites have twice as many species as montane sites. Also, the differentiation in species composition between lowland and montane sites within the same region is more pronounced (63–75% similarity) than that between adjacent regions (96–99% similarity for lowland sites and 83–87% similarity for montane sites). This means that altitudinal preferences affect species composition more strongly than geographical differentiation. The latter is a function of distance, however, while Mexican and Guatemalan lowland (montane) sites share 96% (83%) of the species, these values drop to 74% (72%) when comparing Mexico with Ecuador. Nevertheless, overall floristic similarity is very high, with the lowest value of 54% shared species found between Mexican lowland and Costa Rican montane forest.

We analyzed the structure of foliicolous lichen communities in the northernmost lowland forest of the Neotropics, Los Tuxtlas Tropical Biology Station in Veracruz, Mexico, and its dependence on phorophyte and microclimate. Along a 420‐m long transect with 15 equidistant sampling points, within a 10 m radius of each point, we sampled a total 137 phorophytes and 411 leaves. The phorophytes represented 13 species, with diverse leaf traits regarding size, texture, presence of hairs and/or glands, and longevity, including: Astrocaryum mexicanum (Arecaceae), Chamaedorea ernesti‐augustii (Arecaceae), Costus scaber (Costaceae), Guarea glabra (Meliaceae), Heliconia latispatha (Heliconiaceae), Monstera acuminata (Araceae), Myriocarpa longipes (Urticaceae), Piper hispidum (Piperaceae), Poulsenia armata (Moraceae), Pseudolmedia oxyphyllaria (Moraceae), Salacia megistophylla (Celastraceae), Siparuna thecaphora (Siparunaceae) and Syngonium podophyllum (Araceae). NDMS ordination and cluster analysis grouped the phorophytes into hierarchically structured clusters variously correlated with microsite, phorophyte species and foliicolous lichen species richness. Indicator species analysis revealed statistically significant foliicolous lichen species characteristic for terminal clusters and for phorophyte species. We conclude that the principle of “diversity begets diversity” may apply, in that phorophyte diversity influences the diversity of foliicolous lichen communities through the manifestation of subtle phorophyte preferences, best seen in well‐developed communities on leaves with higher longevity. Thus, well‐preserved forest ecosystems, with a higher diversity of suitable phorophytes, will support a higher diversity of foliicolous lichens, a phenomenon that extents to epiphytes in general.