Limited effects of fire disturbances on the species diversity and structure of ant-plant interaction networks in Brazilian Cerrado

Fire is one of the main natural disturbances in Tropical Savannas, changing the diversity of species, altering the structure of species interactions, and driving the evolution of adaptations. Here, we investigated the effects of fire disturbance on interactions between ants and plants with extrafloral nectaries in Cerrado (Brazilian Savanna). We carried out the study in two different ecosystems of Brazilian Cerrado 700 km apart; Woody Cerrado and Rupestrian Grasslands. We conducted a Before-After-Control-Impact (BACI) experiment, in which the impact was the disturbance caused by fire. In Woody Cerrado, we found no evidence of fire affecting the diversity and composition of plants or its interactions. Fire also did not affect ant diversity but changed the interaction pattern of its interactions by reorganizing the paired interactions between species (i.e., rewiring). However, this effect did not result in changes on the overall structure of the network. In Rupestrian Grasslands, fire also did not affect the diversity and composition of plant species or its interactions, but it did increase the number of ant species and change its composition, leading to a reorganization of the its paired interactions. However, these fire disturbances in the ant level did not affect the overall structure of the network. Our findings indicate that the structure of ant-plant interaction networks is robust to fire disturbances, more in Woody Cerrado than Rupestrian Grasslands, confirming our hypothesis that ant-plant interactions in Cerrado are adapted to fire disturbances. In sum, our study enhances the understanding of the effects of environmental disturbances and the stability of the ant-plant interactions in fire-adapted ecosystems such as Brazilian Cerrado.     

The assembly of plants used as nectar sources by hummingbirds in a Cerrado area of Central Brazil

Studies on hummingbird–plant interactions commonly use a pollination approach emphasizing mutualistic relationships. But floral resources are often used opportunistically by these birds. Plant–pollinator assemblies and pollination sustainability will depend both on the well-adapted plants and other potential floral resources. The Cerrado, Neotropical savannas of Central Brazil, has ca. 7.5 % of its flora supposedly adapted to hummingbird pollination. But detailed information about flowers effectively used by hummingbirds at community level is still lacking. Hence, we recorded all plant species visited by hummingbirds, to determine how these nectariferous flowers were distributed in time and space in different plant formations of a Cerrado area, and also the hummingbird species that visit them. The study was conducted between March 2007 and December 2008 in the Panga Ecological Station. Data regarding flowering phenology, floral morphology and visitation were collected monthly. Forty-six nectariferous species from 39 genera and 17 families were recorded, most with annual flowering dynamics and tubular flowers. But only 21 species had a combination of traits fitting classic ornithophilous syndrome. For the remaining species hummingbird visitation was ascertained from observations at the study site or other sites in the region. Eight hummingbird species occurred in the area and were recorded visiting directly 36 plant species. The study area presented a relatively low number of ornithophilous plants, but a great habitat diversity and many non-ornithophilous plants that hummingbirds used as nectar sources. Therefore, in the studied Cerrado, the diversity of environments and nectariferous plants favour the maintenance of resident and migrant hummingbirds.     

Frugivory and seed dispersal in the Cerrado: Network structure and defaunation effects

Seed dispersal is a fundamental process that is highly threatened by the rapid decline of large-bodied frugivores worldwide. The Brazilian Cerrado, the largest savanna in the world, represents an ideal site for investigating seed dispersal because of its biodiversity, environmental challenges, and knowledge shortfalls. We performed a systematic literature review to analyze the seed dispersal network in the Cerrado and the potential impacts of the defaunation of large-bodied frugivores on it. We considered network metrics, calculated the defaunation index of the frugivore assemblage, and compared traits among different fruit-sized plants and their respective dispersers in the network. We retrieved 1565 interactions involving 193 plant species and 270 animal species. Results show that the Cerrado seed dispersal network is slightly nested and considerably modular, dominated by small- to medium-sized generalist species, such as passerines, marsupials, and mesocarnivores. Nonetheless, large-bodied frugivores like the lowland tapir have a key role in the network due to their great foraging and network integration capacity. The Cerrado frugivore assemblage is moderately defaunated, with possible effects in its interactions with large-fruited plants. The Cerrado's defaunation and functional loss of large vertebrates deserve urgent attention to further understand the impacts on seed dispersal mechanisms and ecosystem functioning.     

The old world salsola as a source of valuable secondary metabolites endowed with diverse pharmacological activities: a review

Salsola is an important genus in the plant kingdom with diverse traditional, industrial, and environmental applications. Salsola species are widely distributed in temperate regions and represent about 45% of desert plants. They are a rich source of diverse phytochemical classes, such as alkaloids, cardenolides, triterpenoids, coumarins, flavonoids, isoflavonoids, and phenolic acids. Salsola spp. were traditionally used as antihypertensive, anti-inflammatory, and immunostimulants. They attracted great interest from researchers as several pharmacological activities were reported, including analgesic, antipyretic, antioxidant, cytotoxic, hepatoprotective, contraceptive, antidiabetic, neuroprotective, and antimicrobial activities. Genus Salsola is one of the most notorious plant genera from the taxonomical point of view. Our study represents a comprehensive review of the previous phytochemical and biological research on the old world Salsola secies. It is designed to be a guide for future research on different plant species that still belong to this genus or have been transferred to other genera.     

Concordance between Phylogeographical and Biogeographical Patterns in the Brazilian Cerrado: Diversification of the Endemic Tree Dalbergia miscolobium (Fabaceae)

Few studies have addressed the phylogeography of species of the Cerrado, the largest savanna biome of South America. Here we aimed to investigate the phylogeographical structure of Dalbergia miscolobium, a widespread tree from the Cerrado, and to verify its concordance with plant phylogeographical and biogeographical patterns so far described. A total of 287 individuals from 32 populations were analyzed by sequencing the trnL intron of the chloroplast DNA and the internal transcribed spacer of the nuclear ribosomal DNA. Analysis of population structure and tests of population expansion were performed and the time of divergence of haplotypes was estimated. Twelve and 27 haplotypes were identified in the cpDNA and nrDNA data, respectively. The star-like network configuration and the mismatch distributions indicated a recent spatial and demographic expansion of the species. Consistent with previous tree phylogeographical studies of Cerrado trees, the cpDNA also suggested a recent expansion towards the southern Cerrado. The diversity of D. miscolobium was widespread but high levels of genetic diversity were found in the Central Eastern and in the southern portion of Central Western Cerrado. The combined analysis of cpDNA and nrDNA supported a phylogeographic structure into seven groups. The phylogeographical pattern showed many concordances with biogeographical and phylogeographical studies in the Cerrado, mainly with the Cerrado phytogeographic provinces superimposed to our sampling area. The data reinforced the uniqueness of Northeastern and Southeastern Cerrados and the differentiation between Eastern and Western Central Cerrados. The recent diversification of the species (estimated between the Pliocene and the Pleistocene) and the ‘genealogical concordances’ suggest that a shared and persistent pattern of species diversification might have been present in the Cerrado over time. This is the first time that an extensive ‘genealogical concordance’ between phylogeographic and phytogeographic patterns is shown for the Cerrado biome.     

The many dimensions of phytochemical diversity: linking theory to practice

Research on the ecological and evolutionary roles of phytochemicals has recently progressed from studying single compounds to examining chemical diversity itself. A key conceptual advance enabling this progression is the use of species diversity metrics for quantifying phytochemical diversity. In this perspective, we extend the theory developed for species diversity to further our understanding of what exactly phytochemical diversity is and how its many dimensions impact ecological and evolutionary processes. First, we discuss the major dimensions of phytochemical diversity – richness, evenness, functional diversity, and alpha, gamma and beta diversity. We describe their potential independent roles in biotic interactions and the practical challenges associated with their analysis. Second, we re‐analyse the published and unpublished datasets to reveal that the phytochemical diversity experienced by an organism (or observed by a researcher) depends strongly on the scale of the interaction and the total amount of phytochemicals involved. We argue that we must account for these frames of reference to meaningfully understand diversity. Moving from a general notion of phytochemical diversity as a single measure to a precise definition of its multidimensional and multiscale nature yields overlooked testable predictions that will facilitate novel insights about the evolutionary ecology of plant biotic interactions.     

Legal deforestation can jeopardize plant diversity conservation in an agricultural frontier in the brazilian Cerrado: a spatial explicit contribution to Santana and Simon (2022)

The work of Santana and Simon (2022) provides a unique database on angiosperm flora in the Cerrado?s agricultural frontier (known as MATOPIBA), revealing that its plant biodiversity remains largely unknown. However, ongoing deforestation combined with areas that can still be legally deforested, has the potential to jeopardize plant conservation in the region if measures to prevent land clearing are not adopted. Based on the databased provided by the authors, high resolution vegetation maps and land tenure data, it is demonstrated that almost 5 Mha of Cerrado vegetation has been converted from 1990 to 2020, and further 10.1 Mha can still be legally cleared, which 1.58 Mha in small, 2.25 Mha in medium and 6.27 Mha in large farms. This has practical implications for biodiversity conservation in the MATOPIBA and, thus, the clearing of “areas where populations of endemic and threatened”, as well as rare, species occur should be avoided. In general, the whole region should be better sampled in order to fill the knowledge gap on its plant diversity, but certain areas could be prioritized to optimize sampling efforts and provide botanical information that inform conservation plans with the objective to avoid the extinction of endemic, threatened and unknown species. Proactive conservation measures are yet palliative because the current environmental legislation still allows the suppression of large extensions of Cerrado vegetation – likely to be converted to mechanized agriculture as soon as it becomes profitable.

     

Boron application increases growth of Brazilian Cerrado grasses

Nutrients are known to limit productivity of plant communities around the world. In the Brazilian Cerrado, indirect evidences point to phosphorus as the main limiting nutrient, but some fertilization experiments suggest that one or more micronutrients might play this role. Boron is one of the essential micronutrients for plants. Agronomically, it received some attention, but it has mostly been neglected in ecological studies assessing the effects of nutrients on plant growth. Through field fertilization and mesocosm experiments in a degraded area in the Cerrado, we show that boron addition increased biomass production of herbaceous vegetation. This could be related to a lower aluminum uptake in the boron fertilized plants. Even considering that plant growth was promoted by boron addition due to aluminum toxicity alleviation, this is the first study reporting boron limitation in natural, noncultivated plant communities and also the first report of this kind in vegetative grasses. These results contribute to disentangling patterns of nutrient limitation among plant species of the species‐rich, aluminum‐rich, and nutrient‐poor Cerrado biome and highlight the potential role of micronutrients, such as boron, for growth of noncrop plants. Understanding how nutrient limitation differs among functional groups in the highly biodiverse areas founded on ancient tropical soils may help managing these plant communities in a changing world.     

Modularity and specialization in bat–fly interaction networks are remarkably consistent across patches within urbanized landscapes and spatial scales

Patterns of specialization and the structure of interactions between bats and ectoparasitic flies have been studied mostly on non-urban environments and at local scales. Thus, how anthropogenic disturbances influence species interactions and network structure in this system remain poorly understood. Here, we investigated patterns of interaction between Phyllostomidae bats and ectoparasitic Streblidae flies, and variations in network specialization and structure across Cerrado patches within urbanized landscapes in Brazil and between local and regional scales. We found high similarity in the richness and composition of bat and fly species across communities, associated with low turnover of interactions between networks. The high specialization of bat–streblid interactions resulted in little connected and modular networks, with the emergence of modules containing subsets of species that interact exclusively or primarily with each other. Such similarities in species and interaction composition and network structure across communities and scales suggest that bat–fly interactions within Cerrado patches are little affected by the degree of human modification in the surrounding matrix. This remarkable consistency is likely promoted by specific behaviors, the tolerance of Phyllostomidae bats to surrounding urbanized landscapes as well as by the specificity of the streblid–bat interactions shaped over evolutionary time.     

Cumin (Cuminum cyminum L.) from Traditional Uses to Potential Biomedical Applications

Cumin (Cuminum cyminum L.) is a small annual and herbaceous plant belonging to the Apiaceae family. It is a multipurpose plant species cultivated in the Middle East, India, China, and several Mediterranean countries, including Tunisia. Its fruit, known as cumin seed, is most widely used for culinary and medicinal purposes. It is generally used as a food additive, popular spice, and flavoring agent in many cuisines. Cumin has also been widely used in traditional medicine to treat a variety of diseases, including hypolipidemia, cancer, and diabetes. The literature presents ample evidence for the biological and biomedical activities of cumin, which have generally been ascribed to its content and action of its active constituents, such as terpens, phenols, and flavonoids. The present paper provides an overview of phytochemical profile, biological activities, and ethnomedical and pharmacological uses of Cumin.     

What happens when fire is too early? Observations of fire-stimulated fruit opening releasing underdeveloped seeds for an endemic Cerrado shrub

The relation of fire with the reproductive process of species from tropical grasslands and savannas has long been investigated. Post-fire flowering is well documented in the Cerrado, but fire-mediated fruit opening and seed dispersal has rarely been described, with very few historical records being known. Even less is known about the effects of different fire seasons on species reproduction. Here, we describe the fire-stimulated fruit opening of Jacaranda ulei, an endemic Cerrado shrub with medical importance to traditional communities. We show that fruits opened within 2 weeks after an early dry season fire, but there were almost no viable seeds as fruits were still immature when burned. When put together with the known records for other species, dry dehiscent fruits and anemochory arise as common traits that favour fire-mediated fruit opening. As these are common attributes in the Cerrado, it is possible that several other species also have fire-stimulated seed dispersal but remain vastly unnoticed and underreported in the literature. Additionally, the peak reproductive effort of these species coincides with the period of prescribed burns of the Integrated Fire Management Program and, consequently, several species could also have their reproductive cycle interrupted to disperse immature seeds. We hope our note encourages further studies on the fire-mediated fruit opening and seed dispersal of Cerrado species, particularly in relation to fire season and seed quality.     

Seed removal patterns of pioneer trees in an agricultural landscape

The seeds of most tropical plants are dispersed by animals, many of which also act as seed predators. Shifts in animal community composition, such as those driven by the clearing of native vegetation, are therefore likely to drive changes in plant recruitment. We used manipulative experiments excluding ants, small rodents, and birds to quantify the relative impacts of these granivores on animal-dispersed pioneer trees (ADPT) in fragments of savanna vegetation and adjacent soy plantations in Brazil’s Cerrado. We found that ants were the main consumers of ADPT seeds, that the rates of seed removal varied with seed size, and that removal rates were higher in savanna fragments than in soy plantations. However, we also found significant interactions between habitat type, seed species, and the type of seed predator being excluded. Our results underscore how challenging it can be to predict the influence of human disturbances on the interactions between plant and animal communities. Because ants, rodents, and birds are Cerrado’s the main seed dispersers and granivores, seedling recruitment in Cerrado landscape mosaics will depend on how these distinct but related processes are each influenced by species-specific patterns of seed size and seed abundance.     

Metabolite Profiling Based on UPLC-Q-TOF-MS/MS and the Biological Evaluation of Medicinal Plants of Chinese Dichocarpum (Ranunculaceae)

The genus Dichocarpum is endemic to East Asia, and many species have been used to treat various diseases. However, phytochemical researches of this genus have been limited to date. In the present study, a metabolomic approach based on UPLC-Q-TOF-MS/MS was used to explore the phytochemical profiles of 10 Chinese Dichocarpum species, and cannabinoid receptor (CB1/CB2) agonistic activities evaluation of these plants was performed. A total of 128 features were putatively annotated, belonging to alkaloids, flavonoids, triterpenes saponins, phenolic acids, and others. Semi-quantitative statistics demonstrated that alkaloids and flavonoids were widely distributed, with the former the most abundant, whereas triterpenes saponins were mainly distributed in D. fargesii and D. wuchuanense. The phylogenetic results obtained from DNA sequencing assigned the 10 species to three groups. Further results of in silico annotation revealed three chemical families and helped determine the characteristic features of the three groups. In addition, the plant extracts of nine species from this genus showed agonistic activity on CB2 receptors. This comprehensive analysis revealed the chemotype distribution and pharmacophylogenetic relationship, to provide clues for the prospective resource utilization of the medicinal plants from the genus Dichocarpum.     

Revealing the reviving secret of the white dead nettle (Lamium album L.)

Lamium album, commonly known as white dead nettle or non-stinging nettle is a flowering herbaceous plant, native throughout Europe, Western Asia and North Africa. From ancient times this plant has been endowed with revival, curative and culinary virtues. In the past, in the traditional and folk medicine white dead nettle has been used mainly for its anti-inflammatory, astringent and anti-septic activity. Nowadays significant amount of knowledge on the efficacy of extracts and raw material of L. album is accumulated and a number of health-related beneficial activities have been scientifically proven. In vitro analyses conducted in various model systems have demonstrated antiviral, antimicrobial, antioxidant, anticancer, cytoprotective, wound healing and other important pharmacological effects. The present review summarizes the recent information on the phytochemical features of this pharmacologically important species. The findings on the chemical composition, biological activities and the pharmacological properties underlying the revival secret of white dead nettle are described and discussed in the view of potential applications for treatment of human diseases. Trends for further research are outlined.     

Shifts in functional traits elevate risk of fire‐driven tree dieback in tropical savanna and forest biomes

Numerous predictions indicate rising CO₂ will accelerate the expansion of forests into savannas. Although encroaching forests can sequester carbon over the short term, increased fires and drought‐fire interactions could offset carbon gains, which may be amplified by the shift toward forest plant communities more susceptible to fire‐driven dieback. We quantify how bark thickness determines the ability of individual tree species to tolerate fire and subsequently determine the fire sensitivity of ecosystem carbon across 180 plots in savannas and forests throughout the 2.2‐million km² Cerrado region in Brazil. We find that not accounting for variation in bark thickness across tree species underestimated carbon losses in forests by ~50%, totaling 0.22 PgC across the Cerrado region. The lower bark thicknesses of plant species in forests decreased fire tolerance to such an extent that a third of carbon gains during forest encroachment may be at risk of dieback if burned. These results illustrate that consideration of trait‐based differences in fire tolerance is critical for determining the climate‐carbon‐fire feedback in tropical savanna and forest biomes.     

Proximity to canopy mediates changes in the defensive chemistry and herbivore loads of an understory tropical shrub,Piper kelleyi

Phytochemical traits are a key component of plant defense theory. Chemical ecology has been biased towards studying effects of individual metabolites even though effective plant defenses are comprised of diverse mixtures of metabolites. We tested the phytochemical landscape hypothesis, positing that trophic interactions are contingent upon their spatial location across a phytochemically diverse landscape. Specifically, intraspecific phytochemical changes associated with vertical strata in forests were hypothesised to affect herbivore communities of the neotropical shrub Piper kelleyi Tepe (Piperaceae). Using a field experiment, we found that phytochemical diversity increased with canopy height, and higher levels of phytochemical diversity located near the canopy were characterised by tradeoffs between photoactive and non‐photoactive biosynthetic pathways. For understory plants closer to the ground, phytochemical diversity increased as direct light transmittance decreased, and these plants were characterised by up to 37% reductions in herbivory. Our results suggest that intraspecific phytochemical diversity structures herbivore communities across the landscape, affecting total herbivory.     

Attractiveness of dung beetles (Coleoptera: Scarabaeinae) to faeces from native mammals in different trophic guilds

Dung beetles are predominantly coprophagous and use mammalian faeces as their main food resource and for offspring rearing. However, these resources are generally ephemeral and scarce. The objective of this study was to verify the attractiveness to dung beetles of the faeces of nine native mammal species of the Cerrado biome in different trophic guilds. This study was conducted during the rainy season (October 2016 to March 2017) in two sensu stricto areas of the Cerrado in the Brasília National Park (PNB), Federal District, Brazil. Pitfalls containing faeces of nine mammals native to the region were used as bait (from three herbivores, three carnivores and three omnivores) for the collection of dung beetles. We collected 203 individuals and 19 species, and the most abundant species were Uroxys aff. thoracalis, Oxysternon palemo, Coprophanaeus spitzi and Diabroctis mirabilis. The most attractive faecal bait was from the omnivorous Chrysocyon brachyurus (32.67% of the individuals and 13 species). This study reveals variation in the attraction of dung beetles to native mammal dung of the Cerrado, with more abundance in the faeces of omnivores and carnivores and less in the faeces of herbivores. The species composition in the carnivore baits did not differ from that of the omnivore baits. These data indicate that changes in Scarabaeinae assemblages result from changes in mammal species such as those that have occurred in the Cerrado biome with the conversion to cattle production, which in recent years has caused intense fragmentation of habitats, expansion of agricultural and livestock activities and the introduction of exotic species. The mammal C. brachyurus, vulnerable to extinction in Brazil, should be a focus for future research, since its faeces support a great diversity of dung beetles in the Cerrado.     

Drug discovery from medicinal plants

Current research in drug discovery from medicinal plants involves a multifaceted approach combining botanical, phytochemical, biological, and molecular techniques. Medicinal plant drug discovery continues to provide new and important leads against various pharmacological targets including cancer, HIV/AIDS, Alzheimer's, malaria, and pain. Several natural product drugs of plant origin have either recently been introduced to the United States market, including arteether, galantamine, nitisinone, and tiotropium, or are currently involved in late-phase clinical trials. As part of our National Cooperative Drug Discovery Group (NCDDG) research project, numerous compounds from tropical rainforest plant species with potential anticancer activity have been identified. Our group has also isolated several compounds, mainly from edible plant species or plants used as dietary supplements, that may act as chemopreventive agents. Although drug discovery from medicinal plants continues to provide an important source of new drug leads, numerous challenges are encountered including the procurement of plant materials, the selection and implementation of appropriate high-throughput screening bioassays, and the scale-up of active compounds.     

Diversity of Cetoniidae (Insecta: Coleoptera) in the Cerrado of Central Brazil

Cetoniidae is a diverse family containing approximately 4,000 species, most of which feed on flowers and fruits. In Brazil, 72 species and 24 genera are recorded. Little is known about this family in the Central region of Brazil, and no research has previously been conducted in the ecologically important Cerrado biome. In this study, we evaluated the diversity and temporal variation of the Cetoniidae in an area of the Cerrado in the Federal District (Brazil) and verified whether the abundance and species richness were influenced by climatic variables. The study was carried out in an area of Cerrado sensu stricto at Água Limpa Farm in Brasília/DF. Beetles were collected weekly from October 2013 to September 2014 using 40 traps baited with banana and pineapple fermented with sugarcane juice. A total of 398 specimens comprising 8 genera and 15 species were collected. We observed temporal variation in abundance and richness of the Cetoniidae in direct relation to the climatic characteristics of the Cerrado, with a greater number of individuals and species appearing in the rainy season. Climatic variables such as temperature and humidity appear to have a significant effect on the diversity of Cetoniidae. This is the first study conducted on this family in Central Brazil.     

Phylogeographic Studies Depict the Role of Space and Time Scales of Plant Speciation in a Highly Diverse Neotropical Region

Phylogeographic studies have merged different disciplines to explain speciation processes at both spatial and time scales. Although the number of phylogeographic extant studies has increased almost exponentially, few have been conducted in tropical countries, especially using plants. Plants are interesting models for such studies because their responses to different habitat conditions are reflected directly in the size and distribution of populations, enabling direct tests of alternative demographic scenarios. Here, we review phylogeographic studies using plant species occurring in different vegetation domains within Brazil, which has the greatest number of plant species in the world. Based on a detailed examination of 41 published articles, we synthesized the current knowledge and discussed the main processes driving the high levels of plant diversity within Brazilian domains. General patterns of diversification could be inferred due to the number of species studied, especially in the Cerrado and Atlantic Forest, the most intensively studied domains (34.1% and 17.1% of the studies, respectively). Distinct vegetation types within both biomes were affected differently by the Pleistocene climatic oscillations. Edaphic conditions and geographical barriers (rivers and mountains) have also influenced the phylogeographical patterns of plants species from Amazonia and the Atlantic Forest. Other Brazilian domains, such as the Caatinga, Pantanal, and Pampas, have been studied to a lesser extent and no common phylogeographic pattern across species could be inferred. Issues regarding past connections between distinct domains also remain unclear, including those affecting the two main forest domains in South America. Future research on plant species will fill these information gaps, improving our understanding of the complex diversification processes affecting the South American biota.