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Understanding the recovery time of vegetation structure and species composition to estimate the resilience of seasonally deciduous tropical forest (SDTF) is fundamental for conservation actions. Related information is still scarce for the semi-arid Brazilian SDTF (locally called Caatinga), which covers more than 800 000 km2 in the northeast of Brazil. We aimed to estimate how long it takes for 11 attributes of vegetation structure and species composition, separately and aggregated, to become similar to an old-growth forest (OGF). The attributes were floristic composition, species richness, Shannon diversity index, plant density, median and maximal diameters and height, basal area, volume and aboveground biomass. The attributes' regeneration ratios were aggregated as an arithmetic average and a geometric average, based on a variance–covariance analysis. The ratios were determined in chronosequences (5, 15, 25 and 35 regeneration years and an OGF) of SDTF, in three different locations in Ceará state. Plant density, which had a unimodal tendency, reached a peak at 15 years and then decreased, although it was still greater than that of the OGF after 35 years. Richness and diversity, with monotonic trends, reached values similar to the OGF. All other attributes, especially floristic composition, volume and biomass, had lower values than the OGF. Based on the aggregate set of attributes, the SDTF was 79 per cent recovered after 35 years of regeneration. The variance–covariance analysis indicated that species richness and aboveground biomass contributed the most to the aggregate ratio of regeneration, while maximum diameter and basal area contributed the least. Recovery of this semi-arid forest takes longer than recovery of other SDTF and requires more than 35 years of regeneration to return to a composition and structure similar to the original one. Therefore, management plans should restrict destructive uses before at least 35 years of regeneration have been reached. [ABSTRACT FROM AUTHOR]

Extrafloral nectaries are known from many plant groups but have rarely been recorded in the large genus Solanum or, in fact, in the family Solanaceae. This study set out to explore the functional role of the extrafloral nectaries recently described in Solanum fernandesii, a species endemic to northeastern Brazil. Light and scanning electron microscopy was used to study the morphoanatomical structure of the nectaries and histochemical analyses were performed to study the chemical composition of the exudates recovered from the glands on the basis of field studies. Light and scanning electron microscopy show that although the petiolar glands in S. fernandesii appear sessile to the naked eye, the glands are short stalked. The epidermis of the glands is composed of short, tightly packed multicellular trichomes. The gland secretions contain a mixture of polysaccharides, pectins, mucilage, proteins, lipids, essential oils, resins, and phenolic compounds on the basis of histochemical tests performed. These findings confirm that the petiolar glands in S. fernandesii are in fact resin glands and not extrafloral nectaries as previously claimed. Our study is the first report of resin glands in the large genus Solanum and we confirm that the glands found in S. fernandesii are unique in the genus. [ABSTRACT FROM AUTHOR]

The relative importance of different community assembly mechanisms varies depending on the environment. According to the stress-dominance hypothesis (SDH), assembly mechanisms range from strong abiotic filtering to competition as the environment becomes more favourable. Most evidence for the SDH comes from studies in gradients of conditions (i.e. abiotic environmental factors that influence the functioning of organisms but are not consumed by them). However, we hypothesized that in resource gradients, competition increases as abiotic filtering becomes stronger. To test our hypothesis, we set up eight plots at different sites along an abiotic severity gradient in the Brazilian semi-arid region (BSAR). In each plot, we identified and measured each woody plant species found, and we recorded 11 functional traits of the main species, dividing the traits into alpha (competition effects) and beta (abiotic filtering effects). We investigated the presence of phylogenetic signal in the traits, the community phylogenetic and phenotypic patterns, and associated the variation in these patterns with the availability of water and soil nutrients. We found phylogenetic signal for most (91%) of the traits analysed. The phylogenetic patterns varied from clustered in stressful sites to random or overdispersed in favourable sites, and we concluded that these phylogenetic patterns were the result of historical processes influencing community assembly in different environments in the BSAR. In general, the phenotypic patterns varied from clustered at the most stressful end to random at less stressful sites. Our results show that in resource gradients, any restriction of the resource (hydric or edaphic) intensifies abiotic filtering and, at the same time, increases the competitive hierarchy among species. On the other hand, stochastic processes seem to have a stronger influence under more favourable abiotic conditions, where abiotic filtering and competition are weaker. Thus, we conclude that the SDH is not supported in resource gradients. [ABSTRACT FROM AUTHOR]

Pseudofrenelopsis and Brachyphyllum are two conifers that were part of the Lower Cretaceous (Aptian) taphoflora of the Crato Formation, Araripe Basin, northeastern Brazil. The former genus includes, so far, P. capillata and indeterminate species, whilst the latter is mainly represented by B. obesum, the most common plant megafossil recovered from that stratigraphic unit. Here, the stem and leaf anatomy of Pseudofrenelopsis sp. and B. obesum specimens is revisited, including the first report of some epidermal and vascular traits for both taxa from the Crato Formation. Along with its paleoecological significance, the new data suggest the presence of more than one Pseudofrenelopsis species in the Aptian taphoflora of the Araripe Basin and further support the taxonomic placement of B. obesum within Araucariaceae. [ABSTRACT FROM AUTHOR]

In this paper we present new synonyms and typifications in Erythroxylum sect. Rhabdophyllum: four taxa are synonymized, three of which at the specific level and one at the infraspecific one, and fourteen lectotypifications are made. [ABSTRACT FROM AUTHOR]

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