Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 32 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Bryophyte richness of soil islands on rocky outcrops is not driven by island size or habitat heterogeneity]]> ABSTRACT The species-area relationship (SAR) is one of the oldest and most studied ecological models, having even served as the foundation of the Theory of Island Biogeography. Nevertheless, the relative importance of habitat heterogeneity to SAR remains poorly understood. Our aim was to test the relative importance of habitat heterogeneity to the SAR of bryophyte assemblages of soil islands of rocky outcrops in the semi-arid region of Brazil. We randomly selected 15 to 20 soil islands on each of four outcrops for a total of 59 soil islands, and calculated the area, mean depth, and number of substrates for each. We used Generalized Linear Models (GLM) to test the SAR with two models, one using species richness and another using life-form richness as the dependent variables. We found no positive relationship between area and habitat heterogeneity, nor any evidence of a SAR, such as a positive relationship between area and species or life-form richness neither between habitat heterogeneity and species richness. However, our findings did show that life-form richness is related to bryophyte species richness on the soil islands. We conclude by suggesting that not only can microclimate influence bryophyte richness, but opportunistic colonization by bryophytes is also important. <![CDATA[Nutrient cycling between soil and leaf litter in the Cerrado (Brazilian savanna) on eutrophic and dystrophic Neosols]]> ABSTRACT We evaluated nutrient cycling by measuring leaf litter production and decomposition in the Brazilian savanna (cerrado sensu stricto) on eutrophic (calcareous) and dystrophic (arenitic) Neosols over the same spatiotemporal scale. We installed three transects in the Cerrado with plots in each Neosol type. Areas along the transects were randomly chosen for determining soil chemical properties, and accumulated leaf litter was collected monthly for a year for analysis. We used litter bags to test for a correlation between loss of dry mass and nutrient release. The calcareous cerrado had higher levels of macronutrients, higher pH, and lower Al compared to the arenitic cerrado. The estimated annual release of leaf litter nutrients in kg ha-1 yr-1 was higher in the calcareous cerrado. Nutrient concentration was significantly higher in different months in the calcareous cerrado, except for S and N. In general, the loss of dry mass was not correlated with nutrient release. Calcareous Neosol is unique to the cerrado sensu stricto, and retains more nutrients and facilitates higher leaf litter chemical quality than cerrado of the same physiognomy on dystrophic soils. Nutrient release is not always related to loss of dry mass, regardless of the amount of leaf litter. <![CDATA[Can the reproductive system of a rare and narrowly endemic plant species explain its high genetic diversity?]]> ABSTRACT The reproductive system of flowering plants can be highly variable, affecting their biology, gene flow and genetic variability among populations. Petunia secreta is a rare annual endemic species of Pedra do Segredo, located in the municipality of Caçapava do Sul, state of Rio Grande do Sul, Brazil. Although rare, the species possesses a high level of genetic variability. We investigated the reproductive system of P. secreta, including fruit production and seed germinability, in order to determine if its reproductive system can explain its genetic diversity. We sampled five populations and conducted five greenhouse hand-pollination treatments: 1) autonomous apomixis; 2) self-pollination; 3) hand self-pollination; 4) geitonogamy; and 5) cross-pollination. We analysed a total of 40 plants, 468 flowers, and 6,500 seeds. Only autonomous apomixis and self-pollination did not produce fruit. No differences in fruit weight were observed among pollination treatments (P &gt; 0.05). Seeds of two colours were produced, with no differences in germinability. Considering all plants, populations, and treatments, the average germinability was 73 % (range 9 % to 100 %). These results, along with other previous studies, indicate that the reproductive systems of P. secreta, and its large effective population size, can explain its high genetic diversity. <![CDATA[Vitality of lichens under different light climates in an Araucaria forest (Pró-Mata RS, South Brazil) as determined by chlorophyll fluorescence]]> ABSTRACT The vitality of 64 lichen species (107 individual lichen thalli) growing under different light climates in an Araucaria forest in South Brazil was analyzed by chlorophyll fluorescence. Study sites were grouped according to their local light availability under full sunlight (about 2200 µmol m-2 s-1): 1 = low light, up to 20 µmol m-2 s-1; 2 = medium light, 20 to 100 µmol m-2 s-1; and 3 = high light, more than 100 µmol m-2 s-1. Maximum quantum yield of photosystem II, as shown by Fv/Fm of dark-adapted samples, was mainly between 0.3 and 0.7, with extremes of below 0.1 and up to 0.85. On average, yields were highest with low light availability (0.66). Groups 1 and 2 were not significantly different from each other, but groups 1 and 3, as well as groups 2 and 3 were. After dark adaptation, lichens were exposed to different light intensities by means of a chlorophyll fluorometer. The results show that low light-adapted lichens exhibit the highest sensitivity to excess light, as was also indicated by the data for non-photochemical quenching. Thus, shade-adapted lichens are obviously well protected from possible damage caused by excess light, which is important when exposed to sun flecks. <![CDATA[Changes of wood anatomical characters of selected species of <em>Araucaria</em>- during artificial charring - implications for palaeontology]]> ABSTRACT Charcoal is widely accepted as evidence of the occurrence of palaeo-wildfire. Although fossil charcoal remains have been used in many studies, investigation into the anatomical changes occurring during charring are few. The present study analyses changes in selected anatomical characters during artificial charring of modern wood of three species of the genus Araucaria (i.e. Araucaria angustifolia, Araucaria bidwillii and Araucaria columnaris). Wood samples of the studied species was charred under controlled conditions at varying temperatures. Measurements of anatomical features of uncharred wood and artificial charcoal were statistically analysed. The anatomical changes were statistically correlated with charring temperatures and most of the parameters showed marked decreases with increasing charring temperature. Compared to the intrinsic variability in anatomical features, both within and between growth rings of an individual plant, the changes induced by temperature account only for a comparatively small percentage of the observed variability. Regarding Araucaria charcoal, it seems possible that at least general taxonomic and palaeoenvironmental implications can be drawn from such material. However, it is not clear so far whether these results and interpretations based on only three taxa, can be generalized for the entire family and anatomically similar fossil taxa or not. <![CDATA[Vegetation structure, carbon sequestration potential and species conservation in four agroforestry systems in Cameroon (Tropical Africa)]]> ABSTRACT As the rate of forest degradation continues to rise, agroforestry may serve as a way of conserving species and carbon sinks. The aim of this study was to assess agrobiodiversity and carbon sequestration potential in agrosystems in Cameroon. Three age groups of agrosystems were studied. Data were collected in 100x50 m2 quadrates. Density ranged from 53.17±0.08 to 1463±50.11; basal area from 2.07±0.00 to 988.39±16.13 m2/ha; Shannon diversity from 3.3±0.71 to 3.68±0.72; Carbon storage from 12.1±0.27 to 54.65±1.38 t C/ha for 1-10-year-old agrosystems with lowest values in neem; 34.78±0.87 to 71.34±1.6 t C/ha for 10-20-year-old stands with lowest values in cashew; 28.24±0.04 to 108.51±2.46 t C/ha for +20-year-old stands with highest values in eucalyptus; Carbon sequestration potential from 296.7±1.98 to 859.33±10.01 t CO2eq/ha. The highest carbon stocks were found in eucalyptus stands (p&lt;0.05). Several endogenous species, especially Afzelia bipindensis (EN), Leptoderris ledermannii (EN), Mansonia altissima (EN), Entandrophragma cylindricum (VU), Nesogordonia papaverifera (VU), Quassia sanguinea (VU), Vitellaria paradoxa (VU), Afzelia africana (VU), Erythrina senegalensis (LC), Detarium microcarpum (LC), senna spectabilis (LC), were assessed. Other overexploited species, especially Carissa edulis, Zanthoxylum zanthoxyloides, Adansonia digitata, Securidaca longepedonculata, were assessed as well. The studied systems are significant CO2eq sinks and refuge centre for agrobiodiversity. <![CDATA[<em>Singerocomus atlanticus</em> sp. nov., and a first record of <em>Singerocomus rubriflavus</em> (Boletaceae, Boletales) for Brazil]]> ABSTRACT Ongoing surveys of macrofungi in the Brazilian Atlantic Forest ecoregion continue to uncover a diverse assemblage of ectomycorrhizal fungi. A new species of Boletaceae, Singerocomus atlanticus sp. nov., is described. Singerocomus rubriflavus, previously known only from Guyana, is recorded for the first time from the Brazilian Atlantic Forest. Phylogenetic data, macro- and microscopic illustrations, and comments are presented for each species. <![CDATA[Growing <em>Periandra mediterranea</em> on post-mining substrate: native Fabaceae with potential for revegetation of degraded rupestrian grasslands in Brazil]]> ABSTRACT Recovery of degraded areas of rupestrian grasslands is hampered mainly by the limited knowledge regarding substrate management and the biology of native species suitable for revegetation of these areas. The aim of our study was to examine the establishment and growth of Periandra mediterranea in different textures of lateritic substrate from a mining-degraded area. The growth of P. mediterranea was evaluated using fine and coarse laterite, both with and without the addition of topsoil. Survival, dry biomass, content of chemical elements and nodulation were evaluated in ten individuals per treatment sixteen months after planting. Although the substrate has low nutrient content, yet high metal concentrations, all plants survived. Plants growing on coarse laterite had 140 % greater biomass than those growing on fine laterite. The addition of topsoil increased biomass in coarse and fine laterite by 46 and 151 %, respectively, and doubled the number of nodulated plants, regardless of grain size. The biomass accumulation of P. mediterranea to a dystrophic substrate revealed its potential for use in the revegetation of degraded areas of rupestrian grasslands. Furthermore, the addition of topsoil facilitated the association of P. mediterranea with nitrogen-fixing bacteria, and increased its growth and capacity to improve substrate fertility. <![CDATA[Temperature and light requirements for germination of species of Velloziaceae from different Brazilian rocky outcrops]]> ABSTRACT Germination is the first step to successful plant establishment. The range of factors that promote germination varies among species. Light and temperature requirements for the germination of species of Velloziaceae were investigated. Seeds of Barbacenia flava, B. markgrafii, B. purpurea, B. williamsi, Vellozia alata, V. compacta, V. glochidea and V. plicata were collected from rocky outcrops located in different Brazilian states and were incubated for germination at 10 to 40 °C in light or dark conditions. Seed mass and length were measured for each species. In general, all species exhibited a high germination percentage at temperatures of 15-40 °C in the light, with the optimal temperature being 25-30 °C for species of Barbacenia and 30 °C for species of Vellozia. Barbacenia flava, V. compacta and, particularly, B. markgrafii, germinated in the dark. In contrast, B. purpurea exhibited an absolute requirement for light and the most restricted range of temperature to germinate. Germination responses and seed traits were related to the microclimate where the species were collected, and germinability in darkness is likely a common trait for species of Velloziaceae from the Espinhaço Range. <![CDATA[Three new species of <em>Marsdenia</em> (Apocynaceae) from Brazil]]> ABSTRACT Three new species of Marsdenia (Apocynaceae) are described from Brazil: M. paganuccii, known from two disjunct populations, one in the Caatinga of Bahia and other in the Atlantic Forest of Espírito Santo; M. paraibana, restricted to the Restinga of Cabedelo National Forest in the Atlantic Forest of Paraíba; and M. trisegmentata, known from two populations in Caatinga, one in Bahia and other in Ceará. Illustrations, a geographic distribution map and comparisons with morphologically similar species are also presented for each species. <![CDATA[Temporal changes in species composition, diversity, and woody vegetation structure of savannas in the Cerrado-Amazon transition zone]]> ABSTRACT Vegetation in the transition between tropical forest and savanna is hyperdynamic and there is evidence that in the absence of fire, forest advances over savanna. Between 2008 and 2013 we evaluated changes in species composition and diversity and in the structure of the woody vegetation of savanna physiognomies in the transition between the Cerrado and Amazon biomes that were fire free for 11 years. The physiognomies form a gradient from savanna woodland (Typical Cerrado - TC), to low woodland (Dense Cerrado - DC), to woodland (locally called Cerradão - CO). We hypothesise that: 1) the more open physiognomies (TC and DC) are more dynamic compared to the closed physiognomy (CO); and 2) in the absence of fire vegetation tends to become more forested. We found that: 1) TC was more dynamic (e.g. greater increases in richness, diversity, and abundance of plants and basal area) than CO and DC; 2) The three physiognomies experienced an increase in basal area and abundance of individuals, but only certain key species contributed to these increases. These results indicate that the open physiognomies were more dynamic than the closed physiognomies, and in the absence of fire the savanna physiognomies became more forested and accumulated biomass. <![CDATA[Evidence of genetic differentiation and karyotype evolution of the sedges <em>Cyperus ligularis</em> L. and <em>C. odoratus</em> L. (Cyperaceae)]]> ABSTRACT The taxonomy of Cyperaceae is complex, with genera like Cyperus harboring species complexes. We analyzed the genetic similarity between Cyperus ligularis L. and C. odoratus L. based on DNA fingerprinting and cytogenetics. Significative genetic differentiation (G ST = 0.363) and low gene flow (N m = 0.877) indicated a clear genetic distinction between the two species. Moreover, the clustering analysis showed two distinct genetic groups, suggesting a lack of evidence for hybridization. The phenogram revealed two different lineages, and although all individuals of C. odoratus were collected from plots close to each other, they possessed greater genetic diversity than that observed among individuals of C. ligularis, which were sampled over a wider geographic range. Variation in chromosome number within the two species exhibited the opposite pattern, indicating greater karyotype stability in C. odoratus with 2n = 72 and 2n = 76, while the diploid number for C. ligularis varied from 2n = 66 to 88. The lower genetic variation in C. ligularis may be a result of the founder effect associated with seed dispersion and clonal reproduction. Field observations and analysis of reproductive biology should enrich the understanding of the genetic structure of the investigated populations and their role in successional processes. <![CDATA[How to analyze germination of species with empty seeds using contemporary statistical methods?]]> ABSTRACT Statistical analysis is considered an important tool for scientific studies, including those on seeds. However, seed scientists and statisticians often disagree on the nature of variables addressed in germination experiments. Statisticians consider the number of germinated seeds to be a binomially distributed variable, whereas seed scientists convert it into a percentage and often analyze it as a normally distributed variable. The requirement for normal adjustment restricts the models of analysis of variance that can be used. Lack of fit requires nonparametric tests, but they are known by their inferential problems. Generalized Linear Models (GLM) can provide better fit to germination variables for any species, including Lychnophora ericoides Mart., because they allow wider probability distributions with fewer requirements. Here we suggest the use of relative germination besides absolute germination for species with seed development problems, such for L. ericoides and others from the campos rupestres. This paper introduces the most current statistical advancements and increases the possibilities for their application in seed science research. <![CDATA[Nutritious tissue in petals of Annonaceae and its function in pollination by scarab beetles]]> ABSTRACT The feeding of pollinating dynastid-scarab beetles on nutritious tissue of Annonaceae flowers results in macroscopically visible gnawing marks on petals. In the present paper, we present and discuss examples of such gnawing marks on Annonaceae from the Cerrado and the Amazon Forest in Brazil. The localization of gnawing marks on the petals and the histochemistry of the nutritious tissues are emphasized. In some species, nutritious tissue is apparently distributed among all petals, while in other species it is more or less diffusely localized. There are also cases in which nutritious tissue occurs only on clearly localized regions of the inner petals. Petals of selected Amazon species were stained, and studied by light and scanning electron microscopy. The nutritious tissue consists of cells with mucilage-rich walls, which contain starch, lipids and/or tannins. Starch and lipids are not only energy-rich food for the beetles but are apparently also “fuel” for metabolic heating of the flowers, which is a further benefit for the pollinators inside the pollination chamber. <![CDATA[Seasonal variation in gas exchange by plants of <em>Erythroxylum simonis</em> Plowman]]> ABSTRACT Erythroxylum simonisis an understory species found in Northeast Brazil. Due to its shaded habitat,E. simonisis subjected to seasonal oscillations of the environment, to which it must respond ecophysiologically. The objective of this study was to evaluate the effects of seasonality on the ecophysiology ofE. simonis in a fragment of Seasonal Semideciduous Forest. Leaf area index, visible sky fraction and photosynthetically active radiation were measured for 10 individuals during the dry and rainy seasons. Soil moisture, temperature and monthly precipitation were measured, as well as photosynthetic rate, stomatal conductance, internal CO2concentration, transpiration, instantaneous water use efficiency, instantaneous carboxylation efficiency and chlorophyll content. Ecophysiological variables were correlated with environmental variables, with a greater association of rainfall and soil moisture with stomatal conductance, transpiration and photosynthetic rate, indicating that water availability has an effect on the ecophysiology ofE. simonis. With the exception of instantaneous carboxylation efficiency, gas exchange exhibited significant differences among the months studied, with the highest values being for months with greater water availability, thus showing that the ecophysiology of the species responds to seasonal changes throughout the year. <![CDATA[What matters when prioritizing a medicinal plant? A study of local criteria for their differential use]]> ABSTRACT The ethnobotanical literature lacks joint analyses of the factors that may influence the differential use of medicinal plants. This study intends to fill that void by evaluating the local criteria for the differential use of medicinal plants in a rural community in Northeastern Brazil. We chose two health problems (influenza and constipation) characterized as diseases by local (emic) classification to address the following hypotheses: (1) the most important medicinal plants are easier to acquire; (2) the most important medicinal plants are perceived as being more efficient; and (3) the most important medicinal plants taste better (greater palatability). The plants mentioned in interviews were ranked according to the perception of their use (dependent variable), the difficulty of their acquisition, their taste and their efficiency (independent variables). The perceived efficiency explained the use of medicinal plants for both diseases, while taste explained the use only for constipation. The final models for ‘influenza’ contained only efficiency, while those for ‘constipation’ contained all three variables. These findings indicate that medicinal categories many not be homogeneous and that different targets may be influenced by different variables. <![CDATA[Distribution, ecology, and reproduction of bryophytes in a humid enclave in the semiarid region of northeastern Brazil]]> ABSTRACT The ready availability of water resources distinguishes the humid forest of Chapada do Araripe, Ceará State, Brazil, from the semiarid vegetation around it. The regional climate demonstrates a marked seasonality of rainfall that affects the ecological strategies of the species found there. We studied the bryophytes of the humid forest of Chapada do Araripe, analyzing their diversity, geographic distributions, and ecological and reproductive aspects. Bryophytes were collected from different substrates using the random-walk method. We gathered information concerning the geographic distribution, functional groups (life forms, light tolerance guilds, and habits) and reproductive aspects of each taxon. We found 76 bryophyte species, predominantly mosses (45 species). Ten new occurrences were recorded for Ceará State, including a new taxon for northeastern Brazil. Most species are widely distributed in that country. Desiccation tolerant (turf) and intermediate (mat and weft) life forms predominated, as well as generalist species in terms of their light requirements. Sixty eight percent of the species demonstrated substrate preferences. Monoicous (67 %) sexual systems predominated over dioicous. The species displayed functional groups and reproductive aspects tolerant to adverse conditions that maximized the use of available resources and allowed their persistence under the seasonal conditions of the forest. <![CDATA[Chromosome numbers and the systematics of tribe Vochysieae (Vochysiaceae)]]> ABSTRACT With five neotropical genera and ca. 220 species, Vochysieae is the largest tribe of Vochysiaceae, comprising more than 90 % of its species. Preliminary phylogenetic analyses with matK sequence data indicated that Vochysieae may be paraphyletic, separated into the clades QRC (Qualea, Ruizterania and Callisthene) and VS (Vochysia, Salvertia). Whether the genera and the infrageneric taxa are artificial is still controversial. In this study, we analyzed the distribution of chromosome numbers in mitotic or meiotic cells among 20 species belonging to the genera Callisthene, Qualea, Salvertia, and Vochysia, that are native and common in Central and Southeast Brazilian forests or savannas. Species of Callisthene and Qualea possessed 2n = 22, while species of Salvertia and Vochysia had 2n = 24 (or n = 12). These chromosome numbers corroborate the recognition of two groups, and also suggest that chromosome evolution based on numerical variation is conservative in these lineages.