The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the distributions and abundances of 85 woody species domesticated by pre-Columbian peoples. Domesticated species are five times more likely than nondomesticated species to be hyperdominant. Across the basin, the relative abundance and richness of domesticated species increase in forests on and around archaeological sites. In southwestern and eastern Amazonia, distance to archaeological sites strongly influences the relative abundance and richness of domesticated species. Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples

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Aim To map and interpret floristic and geoecological patterns across the Amazon basin by combining extensive field data with basin‐wide Landsat imagery and climatic data. Location Amazonia. Taxon Ground truth data on ferns and lycophytes; remote sensing results reflect forest canopy properties. Methods We used field plot data to assess main ecological gradients across Amazonia and to relate floristic ordination axes to soil base cation concentration, Climatologies at High Resolution for the Earth's Land Surface Areas (CHELSA) climatic variables and reflectance values from a basin‐wide Landsat image composite with generalized linear models. Ordination axes were then predicted across all Amazonia using Landsat and CHELSA, and a regional subdivision was obtained using k‐medoid classification. Results The primary floristic gradient was strongly related to base cation concentration in the soil, and the secondary gradient to climatic variables. The Landsat image composite revealed a tapestry of broad‐scale variation in canopy reflectance characteristics across Amazonia. Ordination axis scores predicted using Landsat and CHELSA variables produced spatial patterns consistent with existing knowledge on soils, geology and vegetation, but also suggested new floristic patterns. The clearest dichotomy was between central Amazonia and the peripheral areas, and the available data supported a classification into at least eight subregions. Main conclusions Landsat data are capable of predicting soil‐related species compositional patterns of understorey ferns and lycophytes across the Amazon basin with surprisingly high accuracy. Although the exact floristic relationships may differ among plant groups, the observed ecological gradients must be relevant for other plants as well, since surface reflectance recorded by satellites is mostly influenced by the tree canopy. This opens exciting prospects for species distribution modelling, conservation planning, and biogeographical and ecological studies on Amazonian biota. Our maps provide a preliminary geoecological subdivision of Amazonia that can now be tested and refined using field data of other plant groups and from hitherto unsampled areas.

Aim To assess the relative roles of geologically defined terrain types (environmental heterogeneity) and a major river (physical dispersal barrier) as predictors of ecological structuring and biogeographical differentiation within Amazonian forests.Location Western Brazilian Amazonia, where the Juru a river and its terraces cross a 1000-km-long boundary between two geological formations (the Solimões and Ic ß a Formations). MethodsWe sampled a 500-km stretch of the Juru a with 71 transects (5 m by 500 m) that spanned both the river and the geological boundary. All transects were inventoried for pteridophytes (ferns and lycophytes) and Melastomataceae, and a subset of 39 transects also for palms and Zingiberales. Three surface soil samples were collected from each transect. The data were analysed using ordinations, regression trees, indicator species analyses and Mantel tests. ResultsAll plant groups showed congruent species turnover between geologically defined terrain types, but little evidence of isolation by the river or geographical distance. Soil cation concentration differed between the Solimões Formation and other terrain types and emerged as the main explanatory factor for species turnover. A large proportion of the plant species were significant indicators for specific parts of the soil cation concentration gradient, and these edaphic associations were congruent with those found in other parts of Amazonia. Pteridophytes had a larger proportion of species in the cation-rich soils than the other plant groups did, and palms had a higher proportion of generalists. Main conclusionsThe geological boundary between the Solimões and Ic ß a formations is confirmed as significant floristic turnover zone. As it runs in a north-south orientation for more than 1000 km, the edaphic differences associated with this boundary have wide-ranging implications for speciation and biogeographical patterns in Amazonia.

Aim: To evaluate the relative importance of climatic versus soil data when predicting species distributions for Amazonian plants and to gain understanding of potential range shifts under climate change.Location: Amazon rain forest. Methods:We produced species distribution models (SDM) at 5-km spatial resolution for 42 plant species (trees, palms, lianas, monocot herbs and ferns) using species occurrence data from herbarium records and plot-based inventories. We modelled species distribution with Bayesian logistic regression using either climate data only, soil data only or climate and soil data together to estimate their relative predictive powers. For areas defined as unsuitable to species occurrence, we mapped the difference between the suitability predictions obtained with climateonly versus soil-only models to identify regions where climate and soil might restrict species ranges independently or jointly.Results: For 40 out of the 42 species, the best models included both climate and soil predictors. The models including only soil predictors performed better than the models including only climate predictors, but we still detected a drought-sensitive response for most of the species. Edaphic conditions were predicted to restrict species occurrence in the centre, the north-west and in the north-east of Amazonia, while the climatic conditions were identified as the restricting factor in the eastern Amazonia, at the border of Roraima and Venezuela and in the Andean foothills.Main conclusions: Our results revealed that soil data are a more important predictor than climate of plant species range in Amazonia. The strong control of species ranges by edaphic features might reduce species' abilities to track suitable climate conditions under a drought-increase scenario. Future challenges are to improve the quality of soil data and couple them with process-based models to better predict species range dynamics under climate change. K E Y W O R D SAmazon rain forest, Bayesian logistic regression, cation exchange capacity, climate change, ecological niche models, soil factors, SoilGrids, species distribution models, species range, tropical soils Fittkau, Junk, Klinge, & Sioli, 1975;Higgins et al., 2011;Sombroek, 2000;Tuomisto & Poulsen, 1996). However, studies focused on the Amazonian rain forests and others also found in other biomes). Species occurrence records were obtained from two sources: plot-based inventories and herbarium records. To ensure data consistency, we targeted species that are easy to identify in the field. We included only species that had more than 20 presence records (see further details: Table S1, Appendix S1 in Supporting Information). 28 km at the equator) into two climatic variables: annual precipitation and dry season length, defined as the maximum consecutive number of months with <100 mm of precipitation. | Environmental dataWe used four remote sensing variables that describe terrain and forest structure properties: elevation, percentage tree cover, per- | Modelling frameworkTo evalu...