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This compilation of ferns and lycophytes in Brazil is an update of the one published in 2010 in Catálogo de Plantas e Fungos do Brasil. The methodology consisted in collecting data from regional checklists, taxonomic revisions, and selected databases. Invited specialists improved the list accessing a website housed at the Jardim Botânico do Rio de Janeiro. The results show 1,253 species: 1,111 of ferns and 142 of lycophytes. This number is 6.5% higher than the previous one (1,176 spp.). The percentage of endemic species decreased from 38.2% to 36.7%. We recognized 36 families and 133 genera (vs. 33 families, 121 genera in 2010). The 10 most diverse families are Pteridaceae (196 spp.), Dryopteridaceae (179), Polypodiaceae (164), Hymenophyllaceae (90), Thelypteridaceae (86), Aspleniaceae (78), Lycopodiaceae (64), Selaginellaceae (55), Anemiaceae (51), and Cyatheaceae (45). The three most diverse genera are still Elaphoglossum (87 spp.), Thelypteris (85), and Asplenium (74). The richest phytogeographic domain continues to be in the Atlantic Rainforest with 883 species which also has the largest number of endemic and threatened species, followed by the Amazon Rainforest (503) ResumoEsta compilação de samambaias e licófitas do Brasil é uma atualização daquela de 2010, no Catálogo de Plantas e Fungos do Brasil. A metodologia consistiu na reunião de dados de listas regionais, revisões de grupos e bancos de dados selecionados. Especialistas convidados melhoraram a lista através do acesso a um sítio da web do Jardim Botânico do Rio Janeiro. Os resultados apontam uma diversidade de 1.253 espécies, sendo 1.111 samambaias e 142 licófitas. Este número é 6,5% maior que o anterior (1.176 espécies). As espécies endêmicas decresceram de 38,2% para 36,7%. Foram reconhecidas 36 famílias e 133 gêneros (vs. 33 famílias, 121 gêneros em 2010). As dez famílias mais diversas são: Pteridaceae (196 espécies), Dryopteridaceae (179), Polypodiaceae (164), Hymenophyllaceae (90), Thelypteridaceae (86), Aspleniaceae (78), Lycopodiaceae (64), Selaginellaceae (55), Anemiaceae (51) e Cyatheaceae (45). Os três gêneros mais diversos continuam sendo Elaphoglossum (87 espécies), Thelypteris (85) e Asplenium (74). O Domínio Fitogeográfico mais rico continua sendo a Mata Atlântica (883 espécies) e também com mais espécies endêmicas e ameaçadas, seguido pela Amazônia (503 espécies), Cerrado (269), Pantanal (30), Caatinga (26) e Pampa (oito). Minas Gerais permanece como o estado com maior riqueza (657 espécies vs. 580 em 2010).

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Establishing which factors determine species distributions is of major relevance for practical applications such as conservation planning. The Amazonian lowlands exhibit considerable internal heterogeneity that is not apparent in existing vegetation maps. We used ferns as a model group to study patterns in plant species distributions and community composition at regional and landscape scales. Fern species composition and environmental data were collected in 109 plots of 250 × 2 m distributed among four sites in Brazilian Amazonia. Interplot distances varied from 1 to ca 670 km. When floristically heterogeneous datasets were analyzed, the use of an extended Sørensen dissimilarity index rather than the traditional Sørensen index improved model fit and made interpretation of the results easier. Major factors associated with species composition varied among sites, difference in cation concentration was a strong predictor of floristic dissimilarity in those sites with pronounced heterogeneity in cation concentration. Difference in clay content was the most relevant variable in sites with uniform cation concentrations. In every case, environmental differences were invariably better than geographic distances in predicting species compositional differences. Our results are consistent with the ideas that: (1) the relative predictive capacity of the explanatory variables depend on the relative lengths of the observed gradients; and (2) environmental gradients can be hierarchically structured such that gradients occur inside gradients. Therefore, site‐specific relationships among variables can mask the bigger picture and make it more difficult to unravel the factors structuring plant communities in Amazonia.