Biogeographic history and environmental gradients modulate non-stationary patterns of tropical tree diversity

Here we studied the entire Atlantic Forest hotspot to investigate whether the effect of different environmental predictors depends on the phylogenetic extension and the biogeographical history of different Atlantic Forest sectors. We used occurrence data of 3,183 plant species with arboreal or arborescent habits. We reconstructed climatic stability across 120,000 years using the Random Forest method. Then, we compared the effect of biogeographical history, topographic, and climatic variables on species richness and phylogenetic diversity using Geographically Weighted Regression (GWR) models. Niche conservatism drives the strength and direction of environmental correlates with tree diversity, interacting with the biogeographical and phylogenetic extension considered. Low current climate seasonalities were the main drivers of species richness and phylogenetic diversity variation across the Atlantic Forest. Whereas in higher phylogenetic extension, topographic heterogeneity increased the number of tree species independent of the sector, deep-past climate stability favored phylogenetic diversity by increasing relict lineages of distant clades in all forests, but with anomalies in the southern sector. This investigation yields substantial evidence that the response of the northern and southern sectors of the Atlantic Forest to identical environmental conditions diverges significantly, providing compelling support for the imprint of phylogenetic heritage in generating non-linear diversity patterns.

The commonness of rarity: Global and future distribution of rarity across land plants

A key feature of life's diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant diversity to quantify the fraction of Earth's plant biodiversity that are rare. A large fraction, ~36.5% of Earth's ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth's plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.

Identity and relationships of the Arboreal Caatinga among other floristic units of seasonally dry tropical forests (SDTFs) of north-eastern and Central Brazil

The tree species composition of seasonally dry tropical forests (SDTF) in north-eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche-based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal-limited tree flora. These units should be given the status of eco-regions to help driving the conservation policy regarding the protection of their biodiversity.

Classificação das fitofisionomias da América do Sul cisandina tropical e subtropical: proposta de um novo sistema - prático e flexível - ou uma injeção a mais de caos?

RESUMO O presente trabalho propõe um novo sistema de nomenclatura e classificação fisionômico-ecológica para a vegetação da América do Sul tropical e subtropical a leste dos Andes. A formulação do sistema procura desempenhar o papel de ferramenta da linguagem técnica e científica, mas também resistiu a trazer mais uma visão pessoal sobre as variações da vegetação. Desta maneira, o foco foi para a comunicação pela via da articulação prática e flexível de um conjunto de símbolos. Esta abordagem contrasta com aquelas que associam a precisão da linguagem a uma série de definições rígidas. Por outro lado, a formulação procurou também evitar excessos de liberdade para não perder o alvo prático em meio à anarquia. Foi por esse motivo que a proposta utilizou como ponto de partida o sistema mais familiar ao meio acadêmico: a classificação do IBGE para a vegetação brasileira. Entre as propostas de melhoria destacam-se as possibilidades de combinar símbolos para atender a uma ampla variação da escala espacial e respectivos níveis de detalhamento e de escolher apenas os símbolos com maior poder de descrição em cada caso.

Plant diversity hotspots in the Atlantic coastal forests of Brazil

Plant-diversity hotspots on a global scale are well established, but smaller local hotspots within these must be identified for effective conservation of plants at the global and local scales. We used the distributions of endemic and endemic-threatened species of Myrtaceae to indicate areas of plant diversity and conservation importance within the Atlantic coastal forests (Mata Atlântica) of Brazil. We applied 3 simple, inexpensive geographic information system (GIS) techniques to a herbarium specimen database: predictive species-distribution modeling (Maxent); complementarity analysis (DIVA-GIS); and mapping of herbarium specimen collection locations. We also considered collecting intensity, which is an inherent limitation of use of natural history records for biodiversity studies. Two separate areas of endemism were evident: the Serra do Mar mountain range from Paraná to Rio de Janeiro and the coastal forests of northern Espírito Santo and southern Bahia. We identified 12 areas of approximately 35 km(2) each as priority areas for conservation. These areas had the highest species richness and were highly threatened by urban and agricultural expansion. Observed species occurrences, species occurrences predicted from the model, and results of our complementarity analysis were congruent in identifying those areas with the most endemic species. These areas were then prioritized for conservation importance by comparing ecological data for each.

ANÁLISE FLORÍSTICA DO COMPARTIMENTO ARBÓREO DE ÁREAS DE FLORESTA ATLÂNTICA SENSU LATO NA REGIÃO DAS BACIAS DO LESTE (BAHIA, MINAS GERAIS, ESPÍRITO SANTO E RIO DE JANEIRO)

RESUMO As variações da composição da flora arbórea de 60 áreas de floresta atlântica sensu lato (ombrófilas e semidecíduas) da região das Bacias do Leste, englobando o sul da Bahia, o Espírito Santo, o leste de Minas Gerais e o norte do Rio de Janeiro, são analisadas em articulação com variáveis geográficas e climáticas. Listagens de espécies são fornecidas para 16 destas áreas. Análises multivariadas detectaram três padrões de distribuição. (a) A diferenciação entre florestas ombrófilase semidecíduas na regiãoé floristicamente consistente efortemente correlacionada com a sazonalidade do regime de chuvas. A flora arbórea das florestas semidecíduas é, em boa medida, um subconjunto da flora das florestas ombrófilas, extraindo espécies provavelmente mais eficientes em resistir e competir sob condições de seca mais prolongada. (b) Existe uma diferenciação latitudinal tanto para florestas ombrófilas e semidecíduas, que aproxima floristicamente as duas fisionomias dentro da mesma faixa latitudinal. Este padrão é causado provavelmente por variações térmicas e pluviométricas. As florestas ombrófilas são interrompidas no norte fluminense devido ao clima estacional, mas isto não tem como contrapartida uma disjunção na distribuição de espécies arbóreas. (c) As variações da altitude estão fortemente correlacionadas com a diferenciação interna tanto das florestas ombrófilas como das semidecíduas.