Publicações

Environmental filters and biotic interactions drive species richness and composition in ecotone forests of the northern Brazilian Amazonia

The structure of tree communities in tropical forests depends on environmental filters and biotic interactions such as competition and facilitation. Many ecotone forests in Northern Amazonia are intriguingly populated by tree assemblages characterized by distinct abundances of a single species, Peltogyne gracilipes (Leguminosae). It is unclear whether this pattern solely reflects environmental filters or also antagonistic interactions among species with similar habitat requirements. The aim of this study was to determine the response of species richness and composition to environmental filters, and analyze the role of P. gracilipes in structuring tree communities in ecotone forest areas of the Northern Brazilian Amazonia. We sampled 129 permanent plots along a hydro-edaphic gradient. All arboreal individuals with stem diameter ≥10 cm were measured and identified. Multiple regressions were performed to test the effects of environmental filters, and abundance of P. gracilipes on the tree species richness and composition. Species richness and composition responded to the same filters which, in turn, affected species composition directly and indirectly, through the abundance of P. gracilipes. Our results indicate that both abiotic filters and biotic interactions shape the studied tree communities. P. gracilipes can be considered an indicator species of hydro-edaphic conditions, but also is itself a driver of tree community structure.

Using near-infrared spectroscopy to discriminate closely related species: A case study of neotropical ferns

Identifying plant species requires considerable knowledge and can be difficult without complete specimens. Fourier-transform near-infrared spectroscopy (FT-NIR) is an effective technique for discriminating plant species, especially angiosperms. However, its efficacy has never been tested on ferns. Here we tested the accuracy of FT-NIR at discriminating species of the genus Microgramma. We obtained 16 spectral readings per individual from the adaxial and abaxial surfaces of 100 specimens belonging to 13 species. The analyses included all 1557 spectral variables. We tested different datasets (adaxial + abaxial, adaxial, and abaxial) to compare the correct identification of species through the construction of discriminant models (Linear discriminant analysis and partial least squares discriminant analysis) and cross-validation techniques (leave-one-out, K-fold). All analyses recovered an overall high percentage (> 90%) of correct predictions of specimen identifications for all datasets, regardless of the model or cross-validation used. On average, there was > 95% accuracy when using partial least squares discriminant analysis and both cross-validations. Our results show the high predictive power of FT-NIR at correctly discriminating fern species when using leaves of dried herbarium specimens. The technique is sensitive enough to reflect species delimitation problems and possible hybridization, and it has the potential of helping better delimit and identify fern species.

Amazon tree dominance across forest strata

The forests of Amazonia are among the most biodiverse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary biodiversity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 hyperdominant species account for >50 {%} of all individuals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations.

Delimitação específica e filogeografia do complexo 𝘗𝘳𝘰𝘵𝘪𝘶𝘮 𝘢𝘳𝘢𝘤𝘰𝘶𝘤𝘩𝘪𝘯𝘪 (Aubl.) Marchand (Burseraceae)

O complexo Protium aracouchini (Aubl.) Marchand (CPA) engloba oito espécies de ocorrência na bacia Amazônica, Cerrado, Andes, Escudo das Guianas, e Mata Atlântica. Este trabalho apresenta o resultado de uma investigação integrativa utilizando dados moleculares, espectrais e morfológicos com o objetivo de reconstruir a história filogeográfica do CPA utilizando diferentes técnicas de análise que permitam uma melhor delimitação das espécies deste complexo e a elucidação dos processos históricos responsáveis por sua diversificação. Perguntas específicas visaram: (1) reconstruir a história evolutiva do complexo Aracouchini através de uma abordagem filogeográfica, buscando saber qual é a história demográfica de expansão e contrção das populações do CPA no espaço e no tempo, e como essa história está relacionada aos eventos geológicos e climáticos na América do Sul ocorridos desde a origem do grupo, estimada em 15 milhões de anos? (2) Revisar a delimitação das espécies e a taxonomia do CPA; (3) Investigar a especialização ecológica na diversificação de linhagens do CPA. Apresentamos o resultado desta análise em três capítulos. No primeiro, é apresentada a filogenia molecular do grupo e a proposta de uma árvore de espécies juntamente com testes de delimitação de espécies; também descrevemos quatro espécies novas (P. apostoloanum sp. nov., P. linguipetalum sp. nov., P. makunaimae sp. nov., e P. vicentinii sp. nov.), resultantes dos testes anteriormente citados. No segundo capítulo, é abordada a biogeografia do complexo, inferindo uma árvore filogenética datada e respondendo perguntas relacionadas aos objetivos 2 e 3. No terceiro capítulo, descrevemos uma espécie nova de Protium, P. santamariae, endêmica da Costa Rica e que mantem maiores afinidades com espécies do complexo Protium heptaphyllum (Aubl.) Marchand, pois até então se pensava que havia uma relação mais próxima dessas populações costa-riquenhas com o CPA, hipótese falseada com os resultados do capítulo 1. Por fim, apresentamos uma síntese dos resultados no capítulo de conclusão.

Using near-infrared spectroscopy to discriminate closely related species: A case study of neotropical ferns

Identifying plant species requires considerable knowledge and can be difficult without complete specimens. Fourier-transform near-infrared spectroscopy (FT-NIR) is an effective technique for discriminating plant species, especially angiosperms. However, its efficacy has never been tested on ferns. Here we tested the accuracy of FT-NIR at discriminating species of the genus Microgramma. We obtained 16 spectral readings per individual from the adaxial and abaxial surfaces of 100 specimens belonging to 13 species. The analyses included all 1557 spectral variables. We tested different datasets (adaxial+abaxial, adaxial, and abaxial) to compare the correct identification of species through the construction of discriminant models (LDA, PLS) and cross-validation techniques (leave-one-out, K-fold). All analyses recovered an overall high percentage (>90 %) of correct predictions of specimen identifications for all datasets, regardless of the model or cross-validation used. On average, there was > 95 % accuracy when using PLS-DA and both cross-validations. Our results show the high predictive power of FT-NIR at correctly discriminating fern species when using leaves of dried herbarium specimens. The technique is sensitive enough to reflect species delimitation problems and possible hybridization, and it has the potential of helping better delimit and identify fern species.Competing Interest StatementThe authors have declared no competing interest.

Floristic composition in ecotone forests in northern Brazilian Amazonia: preliminary data

Floristic composition in ecotone forests in northern Brazilian Amazonia: preliminary data

Ecotone has been defined as “a multi-dimensional environmentally stochastic interaction zone between ecological systems with characteristics defined in space and time, and by the strength of the interaction” (Hufkens et al. 2009). This is a known concept to define transitional zones between two or more ecological communities, ecosystems or biotic regions. Ecotone forests, dispersed in northern Brazilian Amazonia, are natural formations which have been largely affected by anthropogenic impacts, such as deforestation and fire. Maracá Ecological Station, State of Roraima, Brazil, is a protected area with extensive representations of ecotone forests in this region of the Amazonia. Forest inventories and floristic surveys are important as they extend our knowledge (1) of forest structure and tree species composition and (2) of tree and palm species ecology in this region of the Amazonia. Both improve our ability to predict changes in plant diversity, considering the future scenarios of climate change in comparison with previous surveys performed in Maracá. We present a forest inventory carried out in 129 plots (10 m x 50 m; 6.45 ha in total) dispersed in a grid (5 km x 5 km) located in a forest zone ecotone in the eastern part of Maracá Ecological Station. All stems (tree + palm) with diameter at breast height ≥ 10 cm were recorded, identified and measured. A total of 3040 stems were recorded (tree = 2815; palm = 225), corresponding to 42 botanic families and 140 identified species. Seven families and 20 genera contained unidentified taxa (12.2%). Sapotaceae (735 stems; 10 species), Leguminosae (409; 24) and Rubiaceae (289; 12) were the most abundant families. Peltogyne gracilipes Ducke (Leguminosae), Pradosia surinamensis (Eyma) T.D.Penn. (Sapotaceae) and Ecclinusa guianensis Eyma (Sapotaceae) were the species with the highest importance value index (~ 25%). The dominance (m2 ha-1) of these species corresponds to > 36% of the total value observed in the forest inventory. Our dataset provides complementary floristic and structure information on tree and palm in Maracá, improving our knowledge of this Amazonian ecotone forest.

Volatile monoterpene 'fingerprints’ of resinous 𝘗𝘳𝘰𝘵𝘪𝘶𝘮 tree species in the Amazon Rainforest

Volatile terpenoid resins represent a diverse group of plant defense chemicals involved in defense against herbivory, abiotic stress, and communication. However, their composition in tropical forests remains poorly characterized. As a part of tree identification, the ‘smell’ of damaged trunks is widely used, but is highly subjective. Here, we analyzed trunk volatile monoterpene emissions from 15 species of the genus Protium in the central Amazon. By normalizing the abundances of 28 monoterpenes, 9 monoterpene ‘fingerprint’ patterns emerged, characterized by a distinct dominant monoterpene. While 4 of the ‘fingerprint’ patterns were composed of multiple species, 5 were composed of a single species. Moreover, among individuals of the same species, 6 species had a single ‘fingerprint’ pattern, while 9 species had two or more ‘fingerprint’ patterns among in- dividuals. A comparison of ‘fingerprints’ between 2015 and 2017 from 15 individuals generally showed excellent agreement, demonstrating a strong dependence on species identity, but not time of collection. The results are consistent with a previous study that found multiple divergent copies of monoterpene synthase enzymes in Protium. We conclude that the monoterpene ‘fingerprint’ database has important implications for constraining Protium species identification and phylogenetic relationships and enhancing understanding of physiological and ecological functions of resins and their potential commercial applications.

Structure and tree species composition in different habitats of savanna used by indigenous people in the Northern Brazilian Amazon

Woody plant diversity from the Amazonian savannas has been poorly quantified. In order to improve the knowledge on wood plants of these regional ecosystems, a tree inventory was carried out in four different habitats used by indigenous people living in the savanna areas of the Northern Brazilian Amazon. The habitats were divided into two types (or groups) of vegetation formations: forest (riparian forest, forest island, and buritizal = Mauritia palm formation) and non-forest (typical savanna). The inventory was carried out in two hectares established in the Darora Indigenous Community region, north of the state of Roraima. The typical savanna is the most densely populated area (709 stems ha-1); however, it has the lowest tree species richness (nine species, seven families) in relation to typical forest habitats: riparian forest (22 species, 13 families and 202 stems ha-1), forest islands (13 species, 10 families and 264 stems ha-1), and buritizal (19 species, 15 families and 600 stems ha-1). The tree structure (density and dominance) of the forest habitats located in the savanna areas studied in this work is smaller in relation to forest habitats derived from continuous areas of other parts of the Amazon. These environments are derived from Paleoclimatic fragmentation, and are currently affected by the impact of intensive use of natural resources as timberselective logging and some land conversion for agriculture.

Decomposition rates of coarse woody debris in undisturbed Amazonian seasonally flooded and unflooded forests in the Rio Negro-Rio Branco Basin in Roraima, Brazil

Estimates of carbon-stock changes in forest ecosystems require information on dead wood decomposition rates. In the Amazon, the lack of data is dramatic due to the small number of studies and the large range of forest types. The aim of this study was to estimate the decomposition rate of coarse woody debris (CWD) in two oligotrophic undisturbed forest formations of the northern Brazilian Amazon: seasonally flooded and unflooded. We analyzed 20 arboreal individuals (11 tree species and 3 palm species) with distinct wood-density categories. The mean annual decomposition rate of all samples independent of forest formation ranged from 0.044 to 0.963 yr−1, considering two observation periods (12 and 24 months). The highest rate (0.732 ± 0.206 [SD] yr−1) was observed for the lowest wood-density class of palms, whereas the lowest rate (0.119 ± 0.101 yr−1) was determined for trees with high wood density. In terms of forest formation, the rates values differ when weighted by the wood-density classes, indicating that unflooded forest (0.181 ± 0.083 [SE] yr−1; mean decay time 11–30 years) has a decomposition rate ∼19% higher than the seasonally flooded formations (0.152 ± 0.072 yr−1; 13–37 years). This result reflects the dominance of species with high wood density in seasonally flooded formations. In both formations 95% of the dead wood is expected to disappear within 30–40 years. Based on our results, we conclude that the CWD decomposition in the studied area is slower in forests on nutrient-poor seasonally flooded soils, where structure and species composition result in ∼40% of the aboveground biomass being in tree species with high wood density. Thus, it is estimated that CWD in seasonally flooded forest formations has longer residence time and slower carbon release by decomposition (respiration) than in unflooded forests. These results improve our ability to model stocks and fluxes of carbon derived from decomposition of dead wood in undisturbed oligotrophic forests in the Rio Negro-Rio Branco Basin, northern Brazilian Amazon.

Ensinando botânica nas florestas no sul do Estado de Roraima

Meliaceae

Sapindaceae em remanescentes de floresta montana no sul da Bahia, Brasil

Este trabalho apresenta um tratamento taxonômico de Sapindaceae em remanescentes de florestas montanas do sul da Bahia, Brasil. O objetivo principal foi realizar o levantamento de Sapindaceae em três remanescentes de floresta montana na região sul do estado da Bahia. O primeiro capítulo apresenta uma visão geral da morfologia do grupo, baseada nas espécies amostradas no estudo florístico. O segundo capítulo trata da descrição de uma nova espécie (Paullinia unifoliolata) encontrada neste inventário. O terceiro capítulo apresenta o resultado do levantamento florístico. Foram encontradas 21 espécies em seis gêneros. Paullinia apresentou a maior riqueza de espécies (7 spp.), seguido de Cupania (5 spp.), Allophylus (4 spp.), Matayba e Serjania (2 spp. cada) e Talisia (1 sp.). Allophylus leucoclados, Cupania furfuracea, Matayba intermedia e Paullinia micrantha representam novos registros para a região Nordeste. Paullinia unifoliolata, espécie recém-descrita a partir deste estudo, é conhecida de uma região entre Arataca e Una. Apenas um espécime não foi determinado especificamente, por não se enquadrar em nenhuma das espécies descritas do gênero (Cupania sp. 1). Todas as espécies de Cupania e cinco de Paullinia são endêmicas do domínio Atlântico. As áreas amostradas neste estudo apresentaram a maior diversidade de espécies de Sapindaceae para o domínio Atlântico, em comparação com outros estudos no mesmo domínio. São apresentadas chave de identificação das espécies, descrições, e informações sobre floração, frutificação, distribuição geográfica e hábitat.

Angiospermas em remanescentes de floresta montana no sul da Bahia, Brasil

A floristic study of three areas of montane Atlantic forest in southern Bahia, Brazil, was carried out. From 2004 to 2008 regular botanical collections were made, principally along trails in the interior of the forest fragments at: the Reserva Serra da Pedra Lascada (SPL), the Reserva Serra das Lontras (SLO) and the Reserva Particular do Patrimônio Natural Serra Bonita (SBO). The species richness of each area was compared to that of the other two, and together to other areas of Atlantic coastal forest in Bahia and southeastern Brazil. For all three areas, a total of 1129 species in 467 genera and 124 families were found. Trees represented 46.9% of the species, followed by herbs (20.1%), epiphytes (19.5%), and vines and lianas (13.5%). The families Araceae, Asteraceae, Bromeliaceae, Fabaceae, Lauraceae, Melastomataceae, Myrtaceae, Orchidaceae, Piperaceae, Poaceae, Rubiaceae, and Solanaceae showed the highest species richness for the three areas together. The genus Psychotria (Rubiaceae) had the highest number of species for all three areas (21 spp.), followed by Miconia (20 spp.), Solanum (20 spp.), Piper (19 spp.), Ocotea (16 spp.), Leandra (16 spp.), Peperomia (15 spp.), and Myrcia (14 spp.). The results confirm the high species diversity of angiosperms in southern Bahia and demonstrate for the first time the presence of species characteristic of montane regions of southeastern Brazil in this region.