Aim  The aim of this study was to use compositional changes in tree species along the Amazon River floodplain in Brazil to identify and characterize biogeographic regions that would serve as broad surrogates for conservation planning.Location  The main course of the Amazon River in Brazil, covering a river distance of approximately 2800 km.Methods  Two sampling methods were employed at specific sites: standardized transects and/or individual‐based samples. Seventy‐three samples were collected from 26 sites at approximately 100‐km intervals along the floodplain. Biogeographic regions were identified by non‐metric multidimensional scaling (NMDS) ordination and by a hierarchical cluster analysis. The relative influence of environmental components (flood depths, annual rainfall, and length of the dry season) on tree species composition and one spatial component (longitude) were analysed by multiple regressions against a one‐dimensional NMDS ordination axis.Results  Based on tree species composition, three main biogeographic regions were identified: a western region between Tabatinga and the Negro River confluence; a central region from the Negro River confluence to the Xingu confluence; and an estuarine region from the Xingu confluence to Santana. The regions identified were consistent using different data sets and analytical techniques. Mixed environmental and spatial effects explained most of the variation, but the spatial effect alone had a greater influence on species composition than environmental effects alone.Main conclusions  The regions delimited in the analyses differed from those based on geomorphology or World Wildlife Fund (WWF) ecoregions. These results reinforce the need for surrogates to be tested against biological data before they are used to shape approaches to conservation planning. Although a protected area coverage of 25% gives the impression of extensive conservation management on the floodplain, less than 1% of the Amazon’s floodplain in Brazil is strictly protected. The significant compositional differences between regions and the strong spatial variation along the Amazon indicate that strict protection areas should be distributed much more evenly within and between regions.

This study conducts a biogeographical review of Aniba in Brazil, including its actual and potential distribution, and a review on the species conservation status. The potential distribution of each Aniba species was modeled using the Brazilian Plants and Fungi Biogeography system, which is interconnected with the SpeciesLink network. A consensus model based on up to five algorithms was used to model the potential distribution of each species. The endemism, conservation status and rarity of each species in Brazil were also analyzed. A total of 3059 records of 30 Brazilian Aniba species were found. In total, 16.1% of the records were excluded because of the lack of valid names, and 53.4% were excluded because of the lack of georeference and name of the person who identified the record. The consensus model showed good results for species with 20 or more pixels. The other species had many errors, and their models could only be used to determine new areas for collections. Nine species were endemic to Brazil, and only three species showed no indicator of rarity. The geographical distribution of Brazilian Aniba species shows a predominantly Amazonian pattern. Only four species are not actually found in the Amazon. Some Amazonian species may also be found in Atlantic Forest areas, and many other species have the potential to live there. Our results indicate that only three species have no conservation problems, whereas 14 species have conservation problems, and 13 other species require further population studies to be best evaluated.

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Resumo Este estudo teve o objetivo de apresentar uma revisão sobre a distribuição conhecida das espécies de Mezilaurus ocorrentes no Brasil e investigar se a distribuição potencial e se o estado de conservação das espécies podem ser estudados com base nos dados existentes nos herbários. A distribuição potencial de Mezilaurus foi modelada através do sistema Biogeografia da Flora e Fungos do Brasil. Foi encontrado um total 804 registros de 16 espécies brasileiras de Mezilaurus. O percentual de perda total de registros foi muito grande (58,3%), especialmente devido à falta de georreferenciamento e determinador (56,4%). A análise da distribuição conhecida revelou novas informações para M. lindaviana, M. navalium, M. sprucei, M. subcordata, M. synandra e M. vanderwerffii. Os modelos de distribuição potencial apresentaram bons resultados para M. itauba, M. crassiramea e M. synandra; contudo foram fortemente influenciados pelo número de registros. A análise de raridade mostrou que cinquenta por cento das espécies apresentaram alto grau de raridade pois ocorrem em áreas e habitat restritos e populações escassas. A situação de conservação baseada na classificação de raridade usando os registros dos herbários apresentou falhas quanto à classificação do tamanho das populações, contudo, mostraram bons resultados sobre a amplitude geográfica e de habitat das espécies.

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