Padrões biogeográficos, funcionais e evolutivos sob o controle de filtros geoquímicos e climáticos na Amazônia

The goal of this study was to reveal the importance of edaphic-geochemical filters and of climate conditions to understand the biogeographic, functional and evolutionary patterns of the Amazonian biodiversity in a scenario of climate change. In the first chapter we used species distribution models to compare the relative importance of soil and climate data to predict species ranges of Amazonian plants. Climate has generally been recognized as the main driver of species distribution at large scales. However, we found that soil attributes were the main predictors of large-scale species distribution. The strong control of species ranges by edaphic features might reduce species’ abilities to track suitable conditions under climate change. In the second chapter, we used an assemblage of understory herbaceous plants (Zingiberales) to predict convergent and divergent functional trait response (specific leaf area, height and seed size) at community level along soil, hydro-topographic and climate gradients. Overall, the functional composition of communities tended to converge following the expectation of classical theory of plant strategy based on fast-slow grow trade-off: highly productive habitats (rich nutrient soil and bottomlands) selected functional traits indicating fast growth strategies. However, the functional composition of communities diverged widely along the broader climatic gradient, being impossible to predict which functional traits prevail in dry regions. These results suggest that functioning of Amazonian forests is tightly linked with geochemical conditions, but many uncertainties remain regarding how climate change will affect the functioning of tropical forests. In the third chapter, we tested an evolutionary model based on intrinsic clade functional strategy, nichebased relationships and past geochemical transformations of Amazonian landscapes driven by Andean uplift. Clades with fast growth strategy had higher diversification rates, higher species richness, arose more recently, were more associated with highly productive habitats, and their origin and diversification dynamics were associated with main geological events of the Miocene. Clades with slow growth strategies had the opposite patterns. These results reveal that, to understand the evolutionary history of Amazonian biodiversity, it is essential to take account of niche and functional aspects of species/clades and past geochemical transformations of landscapes driven by paleogeological events. . In summary, we clearly demonstrate in this thesis that biogeographic, functional and evolutionary patterns in Amazonia are strongly controled by edaphic-geochemical filters. Overlooking the role of theses filters in models of climate change effects on tropical biodiversity may lead to unsatisfactory predictions. Understanding where, how and when these filters act is also essential for designing conservations strategies for an Amazonia under constant change.O objetivo desta tese foi revelar a importância de filtros geoquímicos edáficos e condições climáticas para entender a biogeografia, o funcionamento e a história evolutiva da biodiversidade Amazônica em um contexto de mudanças climáticas. No primeiro capítulo comparamos a importância relativa de dados espaciais de solo e dados climáticos, para prever a macro distribuição de plantas na Amazônia. Na larga escala geográfica, assume-se que as restrições eco fisiológicas determinadas pelo clima representam o principal controle dos limites de distribuição das espécies. No entanto, dados de solo representaram os principais descritores da distribuição de espécies no macro escala. Conclui-se que em um cenário de mudanças climáticas, barreiras edáficas deverão restringir a dispersão das espécies e dificultar o rastreamento de condições climáticas favoráveis. No segundo capítulo, usamos uma assembleia de plantas herbáceas de sub-bosque florestal (Zingiberales) para testarmos se existe convergência e/ou divergência nos traços funcionais (área foliar específica, altura e tamanho das sementes) das comunidades ao longo de gradientes regionais de solo, topografia e clima. No geral, a composição funcional das comunidades tende a convergir para o que é esperado pela teoria clássica custo-benefício das estratégias funcionais ao longo de gradientes de recursos: habitats com maior disponibilidade de recursos (nutrientes e água) selecionam traços funcionais indicadores de estratégias de crescimento rápido e ciclo de vida curto. No entanto, a composição funcional das comunidades divergiu fortemente ao longo do gradiente climático, sendo impossível prever a composição funcional em regiões secas. Esses resultados sugerem que o funcionamento das florestas amazônicas está intrinsicamente relacionado com características do solo e topografia, mas ainda existem muitas incertezas sobre como as mudanças climáticas irão afetar sua estrutura e funcionamento. No terceiro capítulo, testamos um modelo evolutivo baseado em características funcionais intrínsecas de linhagens, relações de nicho e transformações da paisagem amazônica em decorrência do soerguimento dos Andes. As linhagens com estratégia funcional de crescimento rápida apresentaram maiores taxas de especiação, tiveram maior riqueza, originaram-se mais recentemente, estiveram mais associadas com ambientes produtivos, e sua origem e mudanças temporais nas taxas de diversificação estiveram associadas principalmente com eventos geológicos do Mioceno. As linhagens com estratégia funcional de crescimento lento apresentaram o padrão oposto. Estes resultados revelam a importância de características funcionais, relações de nicho e eventos geológicos para compreender a história evolutiva da biota amazônica. Esta tese demonstra claramente que padrões biogeográficos, funcionais e evolutivos na Amazônia estão intimamente relacionados com filtros geoquímicos edáficos. Ignorar os efeitos destes filtros em modelos de mudanças climáticas pode levar a sérios erros de predição. Compreender onde, como e quando estes filtros atuam é um aspecto essencial para a conservação de uma Amazônia em constante mudança

The importance of soils in predicting the future of plant habitat suitability in a tropical forest

Aims: Assessment of the future of biodiversity under climate change has been based on climate-only models. We investigated the effects of including soil information when predicting future suitable areas for selected plant species in Amazonia. Methods: We modelled current and future suitable habitats for 35 plant species and compared results of climate-only models with those obtained when climatic and edaphic variables were included. We considered six climatic scenarios for 2050 using different algorithms and projections of atmospheric CO2 concentration. Results: Twenty-five species distribution models had an AUC > 0.69. Out of those, edaphic variables had the greatest contribution in 11 species models, while climatic variables were more important for 14 species. The inclusion of soil variables affected the size and shape of predicted suitable areas, especially in future models. For nearly half of the species, the size of future suitable areas were smaller in climate+soil models than predicted by climate-only models. Area reduction was more extreme in future scenarios with the higher level of CO2 concentration. Conclusions: Our results highlight the importance of moving beyond climatic scenarios when modelling biodiversity responses to climate change. Failure to include soils in the models can overestimate future habitat suitability for many plant species. © 2019, The Author(s)

Variação florística e diversidade de zingiberales em florestas da Amazônia central e setentrional.

The study of plant community structure and its causes has advanced in the last years, but it is far from complete answers to questions such as the relationship between richness and productivity or the main determinants of the compositional structure and the scale in which they act. The hump-shaped curve observed in relationship between richness and productivity is the main pattern found in plant communities, but with less frequency in the Amazon. Linear relationships or the lack of any relationship may result from lack of coverage of the full productivity gradient. Climate, edaphic factors and spatial variables are commonly identified as important predictors of changes in floristic composition at the regional scale, but with low power of explanation. The low predictive power of most models has at least 3 causes: 1) sampling errors, which led to a community representation that is only a fraction of the real community; 2) errors in the choice of predictors, which may not include all relevant variables and 3) analytical errors, by the use of models imcompatible with the biological structures under study. In this study, my objectives were 1) to understand the relationships between species density, and the floristic variation of Zingiberales communities, and climate, edaphic factors and spatial features in Central and Northern Amazon terra firme forests. 2) to assess whether the application of the method ISOMAP improves the performance of distance matrix models. Composition of Zingiberales, climate (measure by the Walsh index), soil texture and fertility data were acquired in 170 plots (250 x 2 m) distributed over 7 forests sites, covering 800 km along a north-south axis. We used multiple linear regression, ISOMAP, multiple regression of distance matrices and multivariate regression trees to assess the effect of spatial and environmental variables. At the coarse grain, the species density was affected by climate, after accounting for the site variation in soil fertility. At the fine grain, only fertility affected negatively the species density. The total variance explained by the models was twice greater when the dissimilarity matrices were transformed by ISOMAP. No soil texture effect was detected in any analyses. Geographic distance was the main predictor of variation in floristic distances (54%), followed by soil fertility (8,4%) and climate (6,9%). Since climate and geographic distances were highly correlated in this dataset, it is not possible to determine the real cause of the floristic pattern. Soil texture was not a significant predictor in any of the models, contrary to the observed in studies in the mesoscale, and this may reflect different relationships between soil drainage and topography in each region. In a more detailed analysis it was shown that soil fertility determines the formation of different floristic groups only in the region with wetter climates, indicating an interaction between soil fertility and climate. Conclusions: (1) climate and soil fertility can be used in predictive models of floristic variation in the brazilian Amazon, but models reflecting the interaction between these variables must be sought; (2) direct measures of key variables, such as soil drainage must be included in future models, and (3) new study sites must be choose in order to reduce the high correlation between climatic and geographic distances.O estudo sobre os padrões de diversidade em plantas e seus determinantes avançou bastante nos últimos anos, mas respostas completas para questões como qual a verdadeira relação entre riqueza e produtividade ou quais os principais determinantes da estrutura composicional ainda permanecem controversos. A curva em forma de corcova ( hump-shaped ) obtida na relação entre riqueza e produtividade tem sido um dos padrões mais freqüentemente observados em comunidades de plantas, porém com menor freqüência na Amazônia. Relações lineares ou falta de relação entre riqueza e produtividade podem ser resultado de amostras distribuídas por apenas parte do gradiente de produtividade. Variáveis climáticas, edáficas e espaciais têm sido indicadas como importantes preditores de variação de composição florística em escala regional, mas com baixo poder de explicação. A baixa capacidade de predição da maior parte dos modelos pode ter pelo menos 3 causas: 1) erros na amostragem, que fazem com que a comunidade seja apenas uma fração da comunidade real; 2) erros na escolha dos preditores, que podem não incluir todas as variáveis de fato moldam a comunidade e 3) erros na análise, que pode assumir modelos incompatíveis com as estruturas biológicas que se quer modelar. Neste trabalho eu tive como objetivos 1) entender como a densidade de espécies e a variação da composição florística de Zingiberales estão relacionadas com fatores espaciais e características do solo e clima, em florestas de terra firme na Amazônia central e setentrional e 2) avaliar se a aplicação do método ISOMAP melhora o desempenho dos modelos de previsão da variação florística. Dados de composição de espécies de plantas da ordem Zingiberales, clima (medido pelo índice de Walsh), fertilidade e textura do solo foram obtidos em 175 parcelas de 250 x 2 m distribuídas em 7 sítios de florestas, cobrindo 800 km ao longo de um eixo norte-sul. Foram utilizadas regressões múltiplas lineares, ISOMAP, regressão múltipla de matrizes de distância e árvore de regressão multivariada para analisar os efeitos das variáveis espaciais e ambientais. Na maior escala (sítios), a densidade de espécies de Zingiberales foi afetada pelo clima, controlando-se a variação da fertilidade do solo de cada sítio. Na escala de parcelas, apenas a fertilidade afetou negativamente a variação da densidade de espécies. O desempenho dos modelos de predição da variação florística com a matriz de dissimilaridade transformada pelo método ISOMAP foi superior aos modelos com a matriz de Sorensen, explicando quase 50% a mais de variação. A distância geográfica foi o preditor mais importante na explicação da variação das distâncias florísticas (54%), seguido pelas diferenças de fertilidade do solo (8,4%) e clima (6,9%). Como as distâncias climática e geográfica estão altamente correlacionadas neste grupo de dados, é difícil determinar a real causa do padrão florístico. A textura do solo não foi um preditor significativo em nenhum dos modelos, ao contrário do observado em estudos na escala média, o que deve refletir as diferentes relações entre drenagem do solo e topografia nas diferentes regiões analisadas. Uma análise mais detalhada mostrou que a fertilidade determina a formação de grupos florísticos apenas na região de clima úmido, indicando uma interação entre fertilidade do solo e clima. Conclusões: (1) clima e fertilidade do solo podem ser utilizados em modelos preditivos de variação florística espacial na Amazônia brasileira, mas deve-se buscar modelos que reflitam as interações entre estas variáveis; (2) outras formas de medir variáveis ambientais importantes para as plantas, como a drenagem dos solos, devem ser elaboradas para inclusão em novos modelos (3) futuras áreas de estudo devem ser escolhidas com o objetivo de diminuir a alta correlação entre distância climática e geográfica entre os sítios

Validating forest types based on geological and land-form features in central Amazonia

Questions: Are topography-based forest types floristically consistent between sites in central Amazonia? Do broad landform and geological features control site-specific edaphic and floristic variation and therefore obfuscate the floristic classification based on local topographical classes? Is model-based clustering a useful tool for floristic classification? Location: Non-inundated forest of central Amazonia, north of the Amazon River. Methods: We analysed species presence-absence of a group of terrestrial monocot herbs (Zingiberales) in 123 plots (250 × 2 m) concentrated in three sites of non-inundated forests. Distances between plots were 1-140 km. Floristic patterns were extracted by dimensionality reduction using geodesic floristic distance. We applied a model-based cluster analysis (MC) coupled with the Bayesian information criterion to determine the best floristic classification. We used geometric and non-geometric internal evaluators to compare the performance of MC to the agglomerative hierarchical clustering method UPGMA. The floristic clusters were tested for differences in edaphic and topographic features. Landform-geological classes were defined based on geological maps and a digital elevation model. We used the Kappa index and ANOVA to evaluate the agreement between landform-geological classes, floristic clusters and environmental features. Results: The best MC solution found four floristic clusters. Differences in soil chemical properties, which were linked with lithological classes and broad land-form features, explained abrupt floristic changes and floristic differences between the same topographical habitats of different sites. Within poor soils, floristic classes defined by elevation along the soil catena (upland and valley forests) were fuzzy. Valley sandy forest was not floristically consistent across sites due to subtle edaphic variation. Using a non-geometric internal evaluator, MC coupled with geodesic floristic distance estimation performed better overall than UPGMA. Main conclusions: Geological classes defined by lithology and broad landform features control the major variation of edaphic and floristic patterns in central Amazonia. MC proved to be a useful method to classify and interpret floristic patterns. Revised vegetation maps that account for lithology, broad land-form features and edaphic conditions would therefore be a better proxy for regional floristic variation than the presently used simple classes based on position along the catena. © 2013 International Association for Vegetation Science

Beyond climate control on species range: The importance of soil data to predict distribution of Amazonian plant species

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 climate-only 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. © 2017 John Wiley & Sons Lt

Congruence between fish and plant assemblages in drifting macrophyte rafts in Central Amazonia

Macrophyte rafts can enhance fish dispersal in the Amazon River basin, and determining whether raft properties (e.g., size and plant species richness) can predict fish species richness and composition is important in order to understand the underlying factors of fish dispersal. We tested for a relationship between the plant species richness and fish species richness in the rafts and determined whether there exists a significant pattern of concordance between rafts composition and fish assemblages in a River-Lake system close to Manaus, Amazonas, Brazil. We estimated the cover of each species of macrophyte and collected fish in 20 macrophyte rafts of different sizes. Macrophyte species richness was not a good predictor of fish species richness. We found a significant correlation between the compositional similarities of macrophytes and fishes when the data for presence/absence were analyzed, but not when abundance data were used. However, the congruence patterns were clearly related to raft size, and we found a correlation between plants and fishes, using both presence/absence and abundance data, when only large rafts were used in the analysis. For small rafts, there were no significant correlations using any type of data. These findings show that the composition of fish assemblage dispersal in the rafts depends on the composition of macrophytes of which the rafts are composed and on stochastic processes of raft splitting. © Springer Science+Business Media B.V. 2010

Broad Scale Distribution of Ferns and Lycophytes along Environmental Gradients in Central and Northern Amazonia, Brazil

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. © 2012 by The Association for Tropical Biology and Conservation

Discovering floristic and geoecological gradients across Amazonia

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. © 2019 John Wiley & Sons Lt

Predicting environmental gradients with fern species composition in Brazilian Amazonia

Aim: A major problem for conservation in Amazonia is that species distribution maps are inaccurate. Consequently, conservation planning needs to be based on other information sources such as vegetation and soilmaps, which are also inaccurate. We propose and test the use of biotic data on a common and relatively easily inventoried group of plants to infer environmental conditions that can be used to improvemaps of floristic patterns for plants in general. Location: Brazilian Amazonia. Methods: We sampled 326 plots of 250 m × 2 m separated by distances of 1-1800 km. Terrestrial fern individuals were identified and counted. Edaphic data were obtained from soil samples and analysed for cation concentration and texture. Climatic data were obtained from Worldclim. We used a multivariate regression tree to evaluate the hierarchical importance of soils and climate for fern communities and identified significant indicator species for the resultant classification. We then tested how well the edaphic properties of the plots could be predicted on the basis of their floristic composition using two calibration methods, weighted averaging and k-nearest neighbour estimation. Results: Soil cation concentration emerged as the most important variable in the regression tree, whereas soil textural and climatic variation played secondary roles. Almost all the plot classes had several fern species with high indicator values for that class. Soil cation concentration was also the variablemost accurately predicted on the basis of fern community composition (R2 = 0.65-0.75 for log-transformed data). Predictive accuracy varied little among the calibration methods, and was not improved by the use of abundance data instead of presence-absence data. Conclusions: Fern species composition can be used as an indicator of soil cation concentration, which can be expected to be relevant also for other components of rain forests. Presence-absence data are adequate for this purpose, which makes the collecting of additional data potentially very rapid. Comparison with earlier studies suggests that edaphic preferences of fern species have good transferability across geographical regions within lowland Amazonia. Therefore, species and environmental data sets already available in the Amazon region represent a good starting point for generating better environmental and floristic maps for conservation planning. © 2014 International Association for Vegetation Science