No abstract

An attempt is made to summarize what is known about the richness of the total terrestrial angiosperm flora of the "cerrados" (as a complex of formations) in Brazil, based on published surveys and species lists. A "refined" list of arboreal and shrubby species was compiled from a total of 145 individual lists from 78 localities, taking into account synonymy and recent taxonomic changes. The refined list had 1709 references to taxonomic entities at the species level (973 identified with confidence and 31 with aff or cf.), 572 references to generic entities (363 genera identified with confidence), and 210 references to the family level (88 families identified with confidence). There are many unidentified arboreal and shrubby taxa at the specific, generic, and family levels, indicating that a considerable amount of taxonomic research remains to be done on the cerrado flora, and that this flora may be much richer than is generally assumed. Depending on the assumptions made, these data suggest a total of around 1000 to 2000 arboreal and shrubby species and 2000 to 5000 herbaceous ones, yielding estimates for the total cerrado flora (terrestrial angiosperms) ranging from 3000 to 7000 species. These limits, especially the upper one, are dubious, but give an idea of the magnitude of the angiosperm flora in the Brazilian cerrados. Surveys of cerrados are very unevenly distributed, and studies of relatively unknown sites may reveal much more diversity than that presently known.

Cerrado is a species-rich savanna-like vegetation that covers a large area in central Brazil. Soil, and particularly soil fertility, is considered to be the major factor determining the wide and diverse physiognomic-floristic gradients encountered within cerrado vegetation. To describe the vegetational variations within a cerrado in southern Mato Grosso state (15° 21'S, 55° 49'W), a 1 ha transect was located to pass through an interfluvial cerrado and climb a steep talus slope. The vegetational and environmental variations are described by means of field classification, direct gradient analysis and reciprocal averaging ordination. The effects of differences in ground water regime in the interfluvial cerrado and differences in inclination with associated rockiness in the talus cerrado are related to the vegetational variations. As the soils are very similar in texture and in the majority of chemical properties, the role of the above environmental factors was more easily distinguished. In the interfluvial cerrado, the vegetation variations are probably related to the seasonal fluctuation in water table level.

-(Variations in floristic and phytosociological structure of an upper montane forest in Mantiqueira Range, Monte Verde, MG). The upper montane forests are known to have a different floristic composition and phytosociological structure from forests located at lower altitudes. A survey was carried out in an area of upper montane forest of the Mantiqueira Range near Monte Verde, municipality of Camanducaia, Minas Gerais State, Brazil. The main objective of this study was to analyze the effect of an altitudinal gradient on the floristic composition and vegetation structure. Seven blocks, each with five of 10 × 10 m plots, were located at altitudes ranging from 1,820 m to 1,940 m, and all bamboos and trees with GHB ³ 15 cm were sampled. A total of 1,191 individuals were included, belong to 64 tree species and two bamboos in a total of 42 genera and 26 families, including the standing dead individuals. The estimated density was 3,403 ind ha -1 and the value of the Shannon-Wiener (H') index was 3.284 nat ind -1 . The dead biomass had the highest importance value (42.06), followed by Pimenta pseudocaryophyllus (Gomes) Landrum (24.59), Roupala rhombifolia Mart. ex Meisn. (19.98) and Drimys brasiliensis Miers (18.57). The structural parameters maximum canopy height and number of branched individuals were correlated with altitude. Although the altitudinal gradient is relatively short, a considerable degree of species substitution was observed, leading to a well-marked floristic gradient.Key words -altitude, Atlantic Rain Forest, Mantiqueira Range, phytosociology, upper montane forest RESUMO -(Variações na composição florística e na estrutura fitossociológica de uma floresta ombrófila densa alto-montana na Serra da Mantiqueira, Monte Verde, MG). As florestas alto-montanas são reconhecidas por apresentarem composição florística e estrutura fitossociológica distintas das florestas em cotas altitudinais inferiores. Realizou-se um levantamento fitossociológico em uma floresta alto-montana localizada na Serra da Mantiqueira, distrito de Monte Verde, Camanducaia, Minas Gerais. O principal objetivo foi analisar o efeito do gradiente altitudinal na composição florística e na estrutura fitossociológica da vegetação. Foram instalados sete blocos paralelos com cinco parcelas contíguas de 10 × 10 m, distantes 50 m, entre 1.840 e 1.920 m de altitude. Todos os indivíduos arbóreos com CAP ³ 15 cm foram amostrados, assim como as "moitas de bambu" que continham no mínimo 10 perfilhos. Foram amostrados 1.191 indivíduos, pertencentes a 64 espécies arbóreas e duas espécies de bambu, distribuídas entre 42 gêneros e 26 famílias, além da classe de indivíduos mortos. A densidade total equivalente foi de 3.403 ind ha -1 e o índice de diversidade de Shannon-Wiener (H') foi de 3,284 nat ind -1 . A biomassa morta destacou-se pelo elevado valor de importância (42,06), seguida de Pimenta pseudocaryophyllus (Gomes) Landrum (24,59), Roupala rhombifolia Mart. ex Meisn. (19,98) e Drimys brasiliensis Miers (18,57). Entre os parâmetros estruturais...

The floristic composition (trees) of 26 forests in the state of S~o Paulo, Brazil, was compared using cluster analysis and Principal Coordinates Analysis (PCO) with simple Euclidean distance. The results obtained indicate the existence of two floristically distinct groups of forests. One group contains forests from higher areas (above 700 m) with a colder climate (Cfa and Cfb) and includes surveys from Angatuba, Atibaia, Guarulhos, Jundiaf, S~o Jos6 dos Compos and S~o Paulo. The second group is floristically less homogeneous and includes forests of the central and western parts of the state, usually at lower altitudes (500-700 m) and subject to hotter climatic conditions (Cwa).

Comparisons of species richness among assemblages using different sample sizes may produce erroneous conclusions due to the strong positive relationship between richness and sample size. A current way of handling the problem is to standardize sample sizes to the size of the smallest sample in the study. A major criticism about this approach is the loss of information contained in the larger samples. A potential way of solving the problem is to apply extrapolation techniques to smaller samples, and produce an estimated species richness expected to occur if sample size were increased to the same size of the largest sample. We evaluated the reliability of 11 potential extrapolation methods over a range of different data sets and magnitudes of extrapolation. The basic approach adopted in the evaluation process was a comparison between the observed richness in a sample and the estimated richness produced by estimators using a sub‐sample of the same sample. The Log‐Series estimator was the most robust for the range of data sets and sub‐sample sizes used, followed closely by Negative Binomial, SO‐J1, Logarithmic, Stout and Vandermeer, and Weibull estimators. When applied to a set of independently replicated samples from a species‐rich assemblage, 95% confidence intervals of estimates produced by the six best evaluated methods were comparable to those of observed richness in the samples. Performance of estimators tended to be better for species‐rich data sets rather than for those which contained few species. Good estimates were found when extrapolating up to 1.8‐2.0 times the size of the sample. We suggest that the use of the best evaluated methods within the range of indicated conditions provides a safe solution to the problem of losing information when standardizing different sample sizes to the size of the smallest sample.

In a previous study near the summit of Mt. Cuscuzeiro (Ubatuba, SP) (820-1270 m), on the SE Brazilian coast, we found two floristically different forests, one above 1120 m, that appears to have a number of features typical of cloud forests, and another on the lower altitude slopes below. Taking these two forests as reference points, we addressed two questions: (1) What are their floristic relationships with other Atlantic forest subtypes in S-SE Brazil?; (2) Do the cloud forests in this region constitute a particular floristic-phytogeographic formation or are they a subset of their surrounding community? Species from 109 surveys (including Mount Cuscuzeiro) of 83 locations in S-SE Brazil were compiled into a binary (presence-absence) floristic matrix. Analyses of similarity among these samples using clustering (UPGMA, TWINSPAN) and ordination (DCA, PCO and CA) methods were performed. The surveys were divided into six main groups: (1) Cloud Forests; (2) ''Salesópolis'' group (3) Coastal Forests, subdivided between (a) Slope Forests and (b) Coastal Plain (''Restinga'') Forests and Mountaintop Forests (not included in the Cloud Forests group); (4) Araucaria Forests; (5) Inland Seasonal Forests (from below ca. 700 m); and (6) Inland Montane Forests (from above ca. 700 m). The preferential and indicator species of the Cloud Forest group produced by TWINSPAN are presented. The Mount Cuscuzeiro forests from above and from below 1120 m were clustered with the Cloud Forests and the coastal Slope Forests groups, respectively. We concluded that Cloud forests comprise a distinct phytogeographic formation in Brazilian S-SE region.

Morphometric analyses of vegetative and floral characters were conducted in 21 populations of five Pleurothallis (Orchidaceae) species occurring in Brazilian 'campo rupestre' vegetation. A phylogenetic analysis of this species group was also carried out using nuclear ribosomal DNA internal transcribed spacers (ITS1 and ITS2). Results of the ordination and cluster analyses agree with species' delimitation revealed by taxonomic and allozyme studies. The groups formed in ordination analysis correspond to the pollinator groups determined in a previous pollination study. Relationships among the species in the cluster analysis using only vegetative characters are similar to those found in a previous allozyme study, but those indicated by cluster analysis using only floral characters differ. These results support the hypothesis that floral similarities are due to convergence driven by similar pollination mechanisms, and therefore floral traits may not be good indicators of phylogenetic relationships in this group. The results of the phylogenetic analysis support this conclusion to some extent. There is no correlation between genetic (allozyme) and morphological variability in the populations nor in the way this variability is distributed among conspecific populations. We describe a new subspecies of Pleurothallis ochreata based on differences in vegetative and chemical characters as well as geographic distribution. Absence of differentiation in floral characters, attraction of the same pollinator species, interfertility and genetic similarity support the argument for subspecific rather than specific status.