Background: Plant composition changes with topography and edaphic gradients that correlate with soil-water and nutrient availability. Data on soil water for the Amazon Basin are scarce, limiting the possibility of distinguishing between soil and soil-water influences on plant composition. Aim: We tested a new proxy for water table depth, the terrain height above nearest drainage (HAND), as a predictor of composition in trees, lianas, palms, shrubs, and herbs and compared HAND to conventional measures of height above sea level (HASL) and horizontal distances from nearest drainage (HDND). Methods: Plant-species composition in 72 plots distributed across 64 km² of lowland evergreen terra firme forest was summarised using non-metric multidimensional scaling (NMDS). NMDS scores were regressed against estimates of HAND, HASL and HDND. Results: Plant composition was highly correlated with the vertical distance from water table, capturing up to 82% of variation. All life forms showed highest turnover rates in the zone with seasonally water-saturated soils, which can extend 350 m from stream margins. Conclusions: Floristic composition is closely related to water table depth, and HAND appears to be the most robust available topographical metric of soil-water gradients. Brazilian conservation laws protecting 30-m-wide riparian buffers are likely to be too narrow to encompass the full zone of highest floristic turnover and may be ineffective in safeguarding riparian plant diversity.

Leaf gas exchange characteristics were measured in twenty woody species that differ in succession status ranging from pioneer species (PS) to late succession species (LS) in a Brazilian rain-reforestation ecosystem. Photon-saturated photosynthetic rate, calculated per either a leaf area (P _NA) or a dry mass (P _NM) basis, differed among species. P _NA and P _NM were highest in PS and lowest in LS. Variation among species was 3-fold (from 7 to 23 μmol m⁻² s⁻¹) for P _NA, and 5-fold (from 50 to 275 μmol kg⁻² s⁻¹) for P _NM. The highest P _NA (23 μmol m⁻² s⁻¹) and P _NM (275 μmol kg⁻² s⁻¹) values were recorded in PS Croton urucurana, while the lowest P _NA (7 μmol m⁻² s⁻¹) and P _NM (50 μmol kg⁻² s⁻¹) values were recorded in LS Aspidosperma cylindrocarpon. A considerable overlap was recorded between PS and LS in values of stomatal conductance (g _s), transpiration rate (E), and leaf mass to area ratio (ALM). However, C. urucurana also showed highest g _s and E. P _NM was highly correlated with ALM in both PS and LS (r=−0.75 and −0.90, respectively). The high values of instantaneous transpiration efficiency (ITE) and intrinsic water use efficiency (WUE_i) were also observed in the PS when compared with the LS.

Trichomes are epidermal outgrowths generally associated with protection against herbivores and/or desiccation that are widely distributed from ferns to angiosperms. Patterns of topological variation and morphological evolution of trichomes are still scarce in the literature, preventing valid comparisons across taxa. This study integrates detailed morphoanatomical data and the evolutionary history of the tribe Bignonieae (Bignoniaceae) in order to gain a better understanding of current diversity and evolution of trichome types. Two sampling schemes were used to characterize trichome types: (1) macromorphological characterization of all 105 species currently included in Bignonieae; and (2) micromorphological characterization of 16 selected species. Individual trichome morphotypes were coded as binary in each vegetative plant part, and trichome density and size were coded as multistate. Ancestral character state reconstructions were conducted using maximum likelihood (ML) assumptions. Two main functional trichome categories were found: non-glandular and glandular. In glandular trichomes, three morphotypes were recognized: peltate (Pg), stipitate (Sg) and patelliform/cupular (P/Cg) trichomes. Non-glandular trichomes were uniseriate, uni- or multicellular and simple or branched. Pg and P/Cg trichomes were multicellular and non-vascularized with three clearly distinct cell layers. Sg trichomes were multicellular, uniseriate and long-stalked. ML ancestral character state reconstructions suggested that the most recent common ancestor (MRCA) of Bignonieae probably had non-glandular, Pg and P/Cg trichomes, with each trichome type presenting alternative histories of appearance on the different plant parts. For example, the MRCA of Bignonieae probably had non-glandular trichomes on the stems, prophylls, petiole, petiolule and leaflet veins while P/Cg trichomes were restricted to leaflet blades. Sg trichomes were not present in the MRCA of Bignonieae independently of the position of these trichomes. These trichomes had at least eight independent origins in tribe. The patterns of trichome evolution indicate that most morphotypes are probably homologous in Bignonieae and could be treated under the same name based on its morphological similarity and common evolutionary history, in spite of the plethora of names that have been previously designated in the literature. The trichome descriptions presented here will facilitate comparisons across taxa, allowing inferences on the relationsthips between trichome variants and future studies about their functional properties.

Despite the historical efforts to list and organize the taxonomic knowledge about the Brazilian ant fauna, the most diverse in the world, several gaps regarding species distribution data and sampling coverage persist. In an attempt to fill some of these gaps, we here apply a scientometric approach to provide an updated overview of the ants of Brazil based on formal publications on ant diversity in the Brazilian territory. In the last 50 years, ant diversity studies in Brazil revealed 1130 species, corresponding to around 70% of the species known to occur in the country. The Brazilian biomes with the highest number of described species recorded were, respectively, the Amazon Forest (716 species), Atlantic Forest (657 species), Cerrado (389 species), Caatinga (185 species), Pantanal (143 species), and Pampa (86 species). Considering the number and frequency of unidentified species, the genera Azteca, Hypoponera, Pheidole, and Solenopsis represent the main knowledge frontiers regarding taxonomic resolution, with more than 80% of their records associated with morphospecies codes in diversity studies in Brazil. Moreover, around 7.5% of the papers presented inconsistences in their species lists regarding the validity of taxonomic names, and we found studies for which some taxa records are geographically implausible. Besides demonstrating the importance of ecological publications to the ant diversity knowledge in Brazil, our findings highlight a strong sampling bias in ant occurrence data in the country, with species records unevenly distributed across Brazilian biomes. In short, our results constitute valuable information for future projects on ant taxonomy and surveying in Brazilian natural areas.