University of the Andes

Ground water tanks are known to be preferred Aedes aegypti oviposition places providing opportunities for adult and larvae control. Therefore, a dual‐effect insecticidal coating (IC) (alphacypermethrin/ pyriproxyfen) with a slow‐release mechanism and safe for users could be applied within Aedes spp. breeding sites, representing a promising option. Bioassays were designed to determine the mortality and sterilizing effects on gravid mosquitoes exposed to IC. The effect of inhibition of emergence was evaluated in eggs, larvae and pupae exposed in different containers. For the water safety assessment concentrations of active ingredients were determined by reverse phase high performance liquid chromatography (RP‐HPLC) and the health risk was calculated. The IC applied to the interior walls of water‐holding containers showed efficacy against Ae. aegypti in terms of high gravid‐female mortality (81% at 24 h, p < 0.01), sterilizing effect (inhibition of oviposition by 63%, p < 0.01) and emergence inhibition (100% in eggs, L3 and L4; 97% in pupae). The offspring rate was reduced [only 0.15 (38/250) new adults emerged per exposed gravid females as against 11.90 per unexposed female (2976/250) at baseline]. Emergence inhibition was recorded up to 12 months and adult mortality >80% up to 6 months. The use of water stored in treated containers, either for washing or drinking, is not expected to pose a health risk to users. IC applied to domestic water containers has dual and complementary action that reduces Ae. aegypti densities (immature and adult stages). This represents baseline information for a cluster randomized efficacy trial in Colombia.

The adsorption of As(V) and As(III) (0.01–1 mM) on a calcined oxidic lithologic material substrate with pH-dependent surface variable charges, chemically modifiable, was investigated. The substrate was prepared via thermal treatment using a natural lithologic material rich in amphoteric oxides of Fe, Al, Mn and Ti. The calcined substrate was treated with acid media (HCl 0.1) to homogenize the positive charge density on the oxide surface via oxide protonation so that anion adsorption would be favored. A batch experiment was performed on the acid-treated substrate (activated) and non-activated substrate. L-type isotherms were obtained, which fit the Freundlich model. Isotherm constants showed that there was a greater affinity between the activated substrate and As(V) (K = 10.58) compared to As(III) (K = 5.45). The adsorption capacity of the activated substrate was two times greater than that of the non-activated substrate, As(V) (Kact = 10.58 and Knoact = 5.45) vs. As(III) (Kact = 5.45 y Knoact = 2.44), which was due to the greater positive charge density on the activated surface, created by the protonation of the surface oxides. Protons were liberated during the adsorption reaction (As(V): 2.17×10−3 and As(III): 0.96×10−3 mmol/mL). The forms H2AsO4− and H3AsO3 deprotonated when adsorbed by the surface groups M-OH2 + (M: Fe, Al). Kinetic data showed a second-order process for As(V) adsorption and a first-order process for As(III) adsorption. The adsorption rate on the activated substrate was two times greater compared with the non-activated substrate: As(V) (kact = 3.78×10−5 L/mg×min and knoact = 2.16×10−5 L/mg×min) vs. As(III) (kact = 0.055 h−1 and knoact = 0.027 h−1). The tested substrate is potentially useful as a low-cost natural material for arsenic removal from contaminated water.

Lactic acid (LA) is an essential chemical that produces high-value-added products across various industries. However, its traditional production via sugar fermentation raises environmental concerns, highlighting the need for alternative, biomass-based production methods. This study investigates the production of LA from hydroxyacetone (HA) oxidation using a Cu/ZrO₂ catalyst prepared by the incipient impregnation method. The catalyst was characterized through several techniques such as ICP-MS, SEM-EDS, N2-physisorption, XRD, XPS, H2-TPR, N2O chemisorption, NH3-TPD, CO2-TPD, Pyridine FT-IR, and TPO analyses, revealing well-dispersed copper species in the zirconia’s tetragonal phase, imparting distinctive redox and acid-base properties. In this contribution, we progressively assessed some reaction parameters and established conditions, including a temperature of 120 °C, a specific HA concentration, and an HA-to-catalyst ratio, to boost the lactic acid performance. Moreover, computational chemistry calculations of Gibbs free energy on model intramolecular and intermolecular Cannizzaro-type reactions demonstrated a distinct preference for lactic acid formation over pyruvic acid, offering valuable insights into the reaction mechanism and spontaneity. Graphical Abstract

The agricultural use of synthetic pesticides, fertilizers, and growth regulators may represent a serious public health and environmental problem worldwide. All this has prompted the exploration of alternative chemical compounds, leading to exploring the potential of chitosan and PGPB in agricultural systems as a potential biotechnological solution to establish novel agricultural production practices that not only result in fewer adverse impacts on health and the environment but also improve the resilience and growth of the plants. In this work, an analysis of the impact of plant growth-promoting bacteria (PGPB) and chitosan on plant growth and protection has been conducted, emphasizing the crucial bioactivities of the resistance of the plants to both biotic and abiotic stressors. These include inducing phytohormone production, mobilization of insoluble soil nutrients, biological nitrogen fixation, ethylene level regulation, controlling soil phytopathogens, etc. Moreover, some relevant aspects of chitin and chitosan are discussed, including their chemical structures, sources, and how their physical properties are related to beneficial effects on agricultural applications and mechanisms of action. The effects of PGPB and chitosan on photosynthesis, germination, root development, and protection against plant diseases have been compared, emphasizing the intriguing similarities and synergistic effects observed in some of these aspects. Although currently there are limited studies focused on the combined application of PGPB and chitosan, it would be important to consider the similarities highlighted in this work, and those that may emerge in future studies or through well-designed investigations, because these could permit advancing towards a greater knowledge of these systems and to obtain better formulations by combining these bioproducts, especially for use in the new contexts of sustainable agriculture. Thus, it seems feasible to augur a promising near future for these combinations, considering the wide range of possibilities offered by chitinous biomaterials for the development of innovative formulations, as well as allowing different application methods. Likewise, the studies related to the PGPB effects on plant growth appear to be expanding due to ongoing research to test on plants the impacts of microorganisms derived from different environments, whether known or recently discovered, making it a very exciting field of research.

Hypertension is responsible for more than two million deaths due to cardiovascular disease annually in Latin America (LATAM), of which one million occurs before 70 years of age. Hypertension is the main risk factor for cardiovascular morbidity and mortality, affecting between 20 and 40% of LATAM adults. Since the publication of the 2017 LASH hypertension guidelines, reports from different LATAM countries have confirmed the burden of hypertension on cardiovascular disease events and mortality in the region. Many studies in the region have reported and emphasized the dramatically insufficient blood pressure control. The extremely low rates of awareness, treatment, and control of hypertension, particularly in patients with metabolic disorders, is a recognized severe problem in LATAM. Earlier implementation of antihypertensive interventions and management of all cardiovascular risk factors is the recognized best strategy to improve the natural history of cardiovascular disease in LATAM. The 2024 LASH guidelines have been developed by a large group of experts from internal medicine, cardiology, nephrology, endocrinology, general medicine, geriatrics, pharmacology, and epidemiology of different countries of LATAM and Europe. A careful search for novel studies on hypertension and related diseases in LATAM, together with the new evidence that emerged since the 2017 LASH guidelines, support all statements and recommendations. This update aims to provide clear, concise, accessible, and useful recommendations for health professionals to improve awareness, treatment, and control of hypertension and associated cardiovascular risk factors in the region.

Objectives Evaluate the controlled release of silicon from smart polydioxanone suture (Smart PDOs™) and the clinical effect of the Cartesian Technique™ in face lifting. Material and Methods This study was preclinical and clinical trials randomized, uncontrolled, and phase I carried out. Preclinical trials included instrumental analysis of silicon-enriched sutures by light microscopy, electron microscopy, and Ultraviolet-visible (UV-vis) spectroscopy. The clinical trial included 35 patients with primary and secondary rhytides, grade I lipomatosis, and grade I deflation. Polydioxanone (PDO) sutures are inserted following the Cartesian Technique™, a vectorial lift from the intersection of the Cartesian planes of the face. Once the cannulas were inserted with the PDO thread, 0.1 mL of organic silicon was dosed. Turgidity was examined by the pinch test of skin turgor. To measure the position of flaccid or deflated tissues, the scale used was the deflation scale. Results The controlled release of organic silicon from the PDO sutures was verified. Its clinical application revealed that after 8 days the improvement in turgidity, wrinkle reversal, and flaccidity tightening was maintained in 100% of the sample. At 15 days, reversal of rhytides was observed, softening of deep furrows in 80%, and the initial turgor and skin tightening maintained without deflation in 90% of cases. Histopathological findings reveal that silicon synergistically potentiates the tissue effect of the PDO suture, generating greater biostimulation of fibroblasts with better quality collagen fibers, greater restructuring and redensification of the skin, and avoiding the late inflammatory response. Conclusion The Cartesian Technique™ with Smart PDOs™ is an effective protocol for skin replenishment that enhances cell biostimulation through the release of bioactive drugs.

The chemical composition of propolis has a dual plant and animal origin, as it is in pot-honey and pot-pollen, including transformations additionally caused by associated microbes. Colonies of the highly eusocial bee tribes collect resins exuded by plants and use them as structural materials and for immune and defense strategies. Resin exudates are produced by diverse plant tissues, e.g., bark, branches, buds, flowers, fruits, leaves, roots, stems, tubers, trunks, or whole plant. This is the first bibliometric study on plant resin use by bees’ research trends. Research on the use of plant resins by stingless bees and Apis mellifera differs; for example, of the 389 documents retrieved from the Scopus database, 74 were on stingless bees (1985–2022) and 315 on Apis mellifera (1967–2022)—the latter has initiated almost 20 years earlier—Two authors were responsible for 34 publications, 15 on stingless bees from Germany and 19 on A. mellifera from Japan. The Journal of Apicultural Research was at the top with five publications on use of plant resins by stingless bee and Evidence Based Complementary and Alternative Medicine with eight articles on Apis mellifera. Apparently, only moderate interest was shown on research on plant resins collected by bees compared to research on propolis in general. However, publications increased widely during 2015–2022. Research groups from Brazil, Germany, Australia, Indonesia, and Japan focused more on resin use by stingless bees, whereas those from Brazil, United States, Japan, Turkey, and India focused on resin use by Apis mellifera. The productivity and impact of research on plant resin use by stingless bees and A. mellifera were visualized. Further progress for stingless bees was visually networked in co-author networks and keyword co-occurrence using the bibliometrix software. These networks revealed the researchers’ teams and the main topics researched. Their thematic maps had three motor themes for stingless bees and plant resins, propolis and flavonoids, antioxidant, and antibacterial activities. Conceptual maps and dendrograms of author’s keywords showed topical clusters by factorial analysis. This chapter will serve as a distinctive and impactful contribution to bee scientists focused on the use of plant resin by Apinae.

An investigation was completed to review the etymologies of 33 stingless bee genera (1806–2005), including the extinct Proplebeia, and 80 Melipona taxa (1798–2012) – 70 species with 10 subspecies for M. bicolor, M. marginata, M. quadrifasciata, and M. seminigra – from the 391 valid names for species groups recognized in the chapter Meliponini Lepeletier, 1836, based on the original references they provided, and completed with further Greek and Latin research for the given names when the etymology was not included. Each genus was identified with the authority and the year of description, the country distributions, type species – the nominal species that represents a genus or subgenus – and the species. Brief bibliographic notes of the 12 meliponine taxonomists describing and discovering 1–16 genera – individually or co-authored – were our criteria for discussing the 33 genera. A few observations and facts were added to entertain the reader by using anecdotes, and the minute considerations involved in the classification process and discovery of new taxa naming just one group of living organisms like stingless bees.

Beneficial molecules for bee colony nutrition and health are also nutritional and medicinal for humans consuming bee products. Stingless bee species are a source of entomological variability in the honey and pollen they produce, besides the plants they forage and the microbial associations receiving particular attention in classic microbiology, food science, and pharmacy. Fifteen stingless bee taxa from Argentina, Australia, Brazil, Costa Rica, Indonesia, Kenya, Malaysia, Mexico, the Philippines, Tanzania, Thailand, Venezuela, and Vietnam were selected and reviewed. How stingless bees choose their raw materials from available plant resources is one aspect of their social behavior and phylogeny. Nectar or honeydew, pollen, and resin provide phytochemical active ingredients, and microbes are vectored by the bees for the nutritional and medicinal properties of substrates processed in the nest into pot-honey, pot-pollen, cerumen, and propolis. Ten functional metabolites putatively useful for stingless bees and humans showed the chemical diversity of pot-propolis. Morphologies of pollen grains found in honey, pollen, and propolis fingerprinted the botanical origin of stingless bee products common in tropical areas, but these are distinctive in certain biomes. Ethnomedicinal uses of pot-honey, pot-pollen, and pot-propolis of stingless bees were reviewed for different cultures. More robust analyses and detailed modes of administration are suggested. “Honey regulations” was the final topic. A binomial nomenclature may apparently focus on stingless bee honey (SBH) for regulatory applications, and pot-honey for interpreting their biochemical and physicochemical transformations, biological activities, and microbial processing.

Bees transform nectar and honeydew into honey, floral pollen into bee pollen, and resins-latex-gums into propolis. Protective functions and biological activities of propolis apply for the bee nest and apitherapy. This chapter deals with the metadata on published propolis research available in Scopus, which started in 1945, and scaled-up to 7886 documents in 2021, indicating that the research on resins collected by corbiculate bees is in the focus of interest nowadays. The yearly production increased exponentially from 2015 up to 38 documents for stingless bees and 685 for other bees in 2021. Vassya Bankova was the most productive propolis researcher in stingless bee (10 documents) and other bee (99 documents). Similarly, the journal Evidence Based Complementary and Alternative Medicine was at the top for publication numbers on propolis produced by stingless and other bees. Universidade de São Paulo from Brazil was the most relevant institution for stingless bees and other bees. Universidade Estadual de Campinas ranked second for stingless bees and third for other bees. Universidade Estadual Paulista Julio de Mesquita Filho was second for other bees, with a 100 documents less than the first one. Burapha University from Thailand ranked third for stingless bee propolis research, the IOCCP Bulgarian Academy of Science fourth, and other Asian universities from Indonesia and Malaysia were top ten too. From the bibliometric search, the countries with most publications on stingless bees propolis were Brazil, Malaysia, Thailand, Indonesia, and Japan; and on other bees Brazil, United States, Turkey, China, and Japan. Dominance of propolis research by countries did not reflect the leading author from Bulgaria. There was a gap between the low quantity of documents produced on propolis research by about 600 species of stingless bees, and the 35 times more publications by other species of bees, mostly Apis mellifera. Taxonomy of Scopus database was useful to visualize with VOSviewer the co-authorship network map, co-occurrence of authors’ keywords, and the productivity in propolis research of stingless bees and other bees until 2021.

Gastrointestinal (GI) diseases can present with several extraintestinal manifestations, and cutaneous signs and symptoms are most frequent. Although conventionally GI and skin are considered two entirely separate organ systems, they are closely correlated in origin. An increasing amount of data highlights the complex relationship between GI and dermatological conditions. This review article aims to particularly explore the clinical correlation between neoplastic and autoimmune GI disorders and skin manifestations, which serve as clinical indicators of these diseases. Neoplastic diseases including pancreatic cancer, gastric adenocarcinoma, Muir-Torre syndrome, carcinoid syndrome, and malignant and benign colorectal polyposis syndromes can be accompanied by skin conditions like pancreatic panniculitis, acanthosis nigricans, keratoacanthomas, necrolytic migratory erythema, melanotic macules, oral papillomas and osteomas, respectively. Autoimmune diseases including celiac disease, autoimmune liver conditions and inflammatory bowel disease (IBD) have been linked to dermatological manifestations such as xanthomas, morphea, psoriasis, dermatitis herpetiformis, erythema nodosum and epidermolysis bullosa acquisita. The skin manifestations can precede the GI symptoms and indicate the severity of the underlying condition, serving as a significant diagnostic marker earlier in the disease. Resolution of skin findings can also indicate the efficacy of treatment strategies and provide prognostic utility. Further research is essential to outline the underlying mechanisms linking dermatological and GI diseases and there is an immediate need for collaborative efforts between dermatologists and gastroenterologists.

A colony of Tetragonisca angustula nested in a damaged 30 cm diameter porcelain Büchner funnel in a garden. This pharmaceutical hive attracted the attention of J.M.F. Camargo†, who was invited to a conference at the Faculty of Pharmacy, who then transferred the colony to a wooden hive. Six plant resin-beeswax-based materials were collected from the nest. Four types of cerumen: (1) Entrance tube. (2) Involucrum of the brood. (3) Pillars by the food reserve pots. (4) Empty honey pots. (5) Irregular resin deposited on the upper wall. (6) Layered propolis deposited on the indoor lid of the hive. These materials were described for visual, tactile, odor-aroma, and taste attributes. Sensory perception was assessed using an intensity scale of 0–3. The brittle involucrum had the strongest smell. Stickiness to teeth bite was higher in the indoor cover propolis of the hive, but the entrance tube stuck more to the fingertips. Colors varied from tortilla to brunette. The involucrum was not as malleable as the other resin-based materials analyzed. Volatile organic compounds (VOCs) from different chemical classes were identified and quantified by HS-SPME/GC-MS: 11 acids, 7 aldehydes, 16 alcohols, 16 esters, 8 ketones, 17 monoterpenes, 5 oxides, 11 sesquiterpenes, and 4 compounds from other classes; 52/95 of these VOCs were detected in the six beeswax-plant resin-based materials of T. angustula nest, as core VOCs.

The global research on yeasts of the genus Starmerella was not mapped before. This bibliometric review comprised documents published since the creation of the genus Starmerella in 1998. Classic rankings for author, affiliation, country, and source analysis were performed for 131 bibliographic records retrieved from the Scopus core collection database. The findings revealed an evolution of the research field after a group of Candida spp. yeasts were relocated as Starmerella spp. based on the concept of a single species Starmerella bombicola accommodating the teleomorph of Candida bombicola. The dataset on Starmerella (1998–2022) provided information to analyze the trends of research on this yeast, as well as support for future investigation. The bibliometric data on Starmerella presented in this chapter facilitate readers to visualize authors, keywords, articles and journals, and their publication trends. Bibliometrix-R tool utilizes factorial analysis to determine the conceptual structure. The ten most cited documents and the documents with the most contributions were plotted using factorial maps. A dendrogram by hierarchical cluster analysis (HCA) discriminated published research on Starmerella research using keywords Plus in a cluster on phylogenetics and a cluster on fermentation, sophorolipid, and controlled studies on metabolism. The thematic evolution maps visualized a current motor theme for Starmerella bombicola, biosynthesis, and sophorolipid. This landscaping can guide the formulation of novel scientific projects as well as support applied policies on antimicrobial activity, genomics, metabolism, and wine industry domains using Starmerella species.

More than 600 species of stingless bees (Hymenoptera, Apidae, Meliponini) produce honey in cerumen pots, with greater diversity than unifloral honey studied for Apis mellifera. Exceptionally, 500 of them are Neotropical meliponines that evolved since the Late Cretaceous Period, the date of the oldest bee fossil Cretotrigona prisca. Microbes associated with stingless bees may have 80 mya-shared nests and traits. In this review, importance is given to the SB species, authorities, years, ethnic names, geographical distribution, and type locality, available for Neotropical (America) in a reference chapter, but scattered for Paleotropical (Africa and Indo-Malaysia/Australasia). A summary list of these microorganisms was tabulated with corresponding substrates for each SB, 3 actinomycetes, 22 bacteria, 38 filamentous fungi, and 40 yeasts. Not all of them reached species identification, phyla, 3 classes of a phylum, family, and genus level. In addition to the microbiota, gut microbiome, and metabolites identified and quantified in their pot-food, microbial cell factories have been slowly demonstrated or suspected in recent contributions from Australia, Brazil, Ecuador, Indonesia, Kenya, Malaysia, and Tanzania. Microbiology, food science, and genomics come together to illustrate a few metabolites: 1. Alcohols: Ethanol, glycerol, isoamylic. 2. Aliphatic organic acids (AOA): Acetic, gluconic, lactic, oxalic, succinic, tartaric. 3. Amino acids: Phenylalanine, proline, pyroglutamic acid. 4. Antibiotics: Meliponamycin A, B, recently discovered as microbial metabolites in Melipona scutellaris. 5. Diphenylether: Asterric acid, 6. Polyketide pigments: Monascin. 7. Phenolic acids: 3-Phenyllactic acid. 8. Polyols: 2,3-Butanediol. 9. Statins: Lovastatin. 10. Steroids: Ergosterol. 11. Sugars: Dihydroxyacetone, maltose, raffinose, trehalulose, turanose. 12. Surfactants. 13. Vitamins: Ascorbic acid. Microbial data was retrieved from two genera, 27 Neotropical, and 13 Paleotropical (eight African, three Australasian, two Indo-Malaysian) SB species. Metabolites were studied in four genera and 20 Neotropical SB species, and 12 Paleotropical species (7 African, 3 Australasian, 2 Indo-Malaysian). The Scaptotrigona genus, and seven Neotropical species, the African Paleotropical Axestotrigona ferruginea, the three Australasian, and the two Indo-Malaysian stingless bee species were studied by both approaches.

Medicinal properties of propolis across a broad spectrum of diseases are ancestral knowledge constantly evidenced while slow to reveal mechanisms of action. Stingless bee propolis used in this review originated from the following stingless bees: Brazil (Melipona fasciculata, Melipona quadrifasciata quadrifasciata, Scaptotrigona sp., Scaptotrigona aff. postica, Tetragonisca angustula), India (Tetragonula sp.), Indonesia (Wallacetrigona incisa), the Philippines (Tetragonula biroi), Thailand (Tetragonula laeviceps, Tetrigona apicalis, Tetrigona melanoleuca), Vietnam (Lisotrigona furva). Five pathologies were selected for this review: cancer, dental plaque, microbial infections, glycemic imbalance, and respiratory disorders. Veterinary uses and in silico approaches were included. Cellular and molecular mechanisms of action elicited by propolis (granules, EEP, and HEP) involved the following: antiproliferative action, adhesion capacity, apoptosis, cell cycle arrest at the G0/G1 phase, cytostatic and cytotoxic action, inflammatory enzymes, inhibition of COX-2, integrity of cell wall and membrane, mRNA gene expression, p21 protein expression, and pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). A note on the geographical origin of propolis and a further note on stingless bee identifications are included. Finally, pharmacological propolis applications need propolis standardization, verified mechanisms of action, and more clinical trials to validate experimental findings. They all create opportunities for new research.

Ethnomedicinal uses of honey value its nutritional and medicinal properties to attain general health, diseases prevention or treatment for particular illness. Madu kelulut or stingless bee honey is produced by Meliponini species and the honey referred as superfood in Malaysia. The honey is a complete natural food product that provide safe source of energy via low GI trehalulose sugar, nourished with nutrients, vitamins, amino acids and good bacteria that is formed via unique natural pot-bioreactor processing. The honey is gaining attention for its high antioxidant levels, antimicrobial properties, anti-inflammatory, unique composition and taste. Studies revealed multiple foundations and evidence-based that the madu kelulut is highly beneficial for human possessing a promising niche in the health supplement industry with economic importance projected up to USD700 million in local markets. Honeyomics of madu kelulut aims at understanding the economic importance factors that contribute to the entire mark-up of madu kelulut as general guides for standards and the functional properties of madu kelulut. Several milestones (2005–2023) have been achieved which acknowledge the strategic development and ecosystem for the madu kelulut industry in Malaysia. Further efforts to safeguards the quality and authenticity of stingless bee honey via modernisation, capacity building and market expansion could encourage for scale-up and solidifying Malaysia’s position as a key player in the global stingless bee honey industry, providing economic benefits while preserving natural resources for future generations.

Tree growth and longevity trade-offs fundamentally shape the terrestrial carbon balance. Yet, we lack a unified understanding of how such trade-offs vary across the world’s forests. By mapping life history traits for a wide range of species across the Americas, we reveal considerable variation in life expectancies from 10 centimeters in diameter (ranging from 1.3 to 3195 years) and show that the pace of life for trees can be accurately classified into four demographic functional types. We found emergent patterns in the strength of trade-offs between growth and longevity across a temperature gradient. Furthermore, we show that the diversity of life history traits varies predictably across forest biomes, giving rise to a positive relationship between trait diversity and productivity. Our pan-latitudinal assessment provides new insights into the demographic mechanisms that govern the carbon turnover rate across forest biomes.

We describe the geographical variation in tree species composition across Amazonian forests and show how environmental conditions are associated with species turnover. Our analyses are based on 2023 forest inventory plots (1 ha) that provide abundance data for a total of 5188 tree species. Within-plot species composition reflected both local environmental conditions (especially soil nutrients and hydrology) and geographical regions. A broader-scale view of species turnover was obtained by interpolating the relative tree species abundances over Amazonia into 47,441 0.1-degree grid cells. Two main dimensions of spatial change in tree species composition were identified. The first was a gradient between western Amazonia at the Andean forelands (with young geology and relatively nutrient-rich soils) and central–eastern Amazonia associated with the Guiana and Brazilian Shields (with more ancient geology and poor soils). The second gradient was between the wet forests of the northwest and the drier forests in southern Amazonia. Isolines linking cells of similar composition crossed major Amazonian rivers, suggesting that tree species distributions are not limited by rivers. Even though some areas of relatively sharp species turnover were identified, mostly the tree species composition changed gradually over large extents, which does not support delimiting clear discrete biogeographic regions within Amazonia.