North American tree migration paced by climate in the West, lagging in the East.

Tree fecundity and recruitment have not yet been quantified at scales needed to anticipate biogeographic shifts in response to climate change. By separating their responses, this study shows coherence across species and communities, offering the strongest support to date that migration is in progress with regional limitations on rates. The southeastern continent emerges as a fecundity hotspot, but it is situated south of population centers where high seed production could contribute to poleward population spread. By contrast, seedling success is highest in the West and North, serving to partially offset limited seed production near poleward frontiers. The evidence of fecundity and recruitment control on tree migration can inform conservation planning for the expected long-term disequilibrium between climate and forest distribution.

Is there tree senescence? The fecundity evidence.

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current estimates are dominated by overrepresentation of small trees in regression models. We combined global fecundity data, including a substantial representation of large trees. We compared size-fecundity relationships against traditional allometric scaling with diameter and two models based on crown architecture. All allometric models fail to describe the declining rate of increase in fecundity with diameter found for 80% of 597 species in our analysis. The strong evidence of declining fecundity, beyond what can be explained by crown architectural change, is consistent with physiological decline. A downward revision of projected fecundity of large trees can improve the next generation of forest dynamic models.

Genomic and metabolomic insights into the antimicrobial compounds and plant growth-promoting potential of Bacillus velezensis Q-426.

BACKGROUND: The Q-426 strain isolated from compost samples has excellent antifungal activities against a variety of plant pathogens. However, the complete genome of Q-426 is still unclear, which limits the potential application of Q-426. RESULTS: Genome sequencing revealed that Q-426 contains a single circular chromosome 4,086,827 bp in length, with 4691 coding sequences and an average GC content of 46.3%. The Q-426 strain has a high degree of collinearity with B. velezensis FZB42, B. velezensis SQR9, and B. amyloliquefaciens DSM7, and the strain was reidentified as B. velezensis Q-426 based on the homology analysis results. Many genes in the Q-426 genome have plant growth-promoting activity, including the secondary metabolites of lipopeptides. Genome mining revealed 14 clusters and 732 genes encoding secondary metabolites with predicted functions, including the surfactin, iturin, and fengycin families. In addition, twelve lipopeptides (surfactin, iturin and fengycin) were successfully detected from the fermentation broth of B. velezensis Q-426 by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS/MS), which is consistent with the genome analysis results. We found that Q-426 produced indole-3-acetic acid (IAA) at 1.56 mg/l on the third day of incubation, which might promote the growth of plants. Moreover, we identified eighteen volatile compounds (VOCs, including 2-heptanone, 6-methylheptan-2-one, 5-methylheptan-2-one, 2-nonanone, 2-decanone, 2-undecanone, 2-dodecanone, 2-tridecanone, 2-tetradecanone, 2-nonadecanone, pentadecanoic acid, oleic acid, dethyl phthalate, dibutyl phthalate, methyl (9E,12E)-octadeca-9,12-dienoate), pentadecane, (6E,10E)-1,2,3,4,4a,5,8,9,12,12a-decahydro-1,4-methanobenzo[10]annulene, and nonanal) based on gas chromatograph-mass spectrometer (GC/MS) results. CONCLUSIONS: We mined secondary metabolite-related genes from the genome based on whole-genome sequence results. Our study laid the theoretical foundation for the development of secondary metabolites and the application of B. velezensis Q-426. Our findings provide insights into the genetic characteristics responsible for the bioactivities and potential application of B. velezensis Q-426 as a plant growth-promoting strain in ecological agriculture.

Biosynthetic Profile in the Co-culture of Aspergillus sydowii and Bacillus subtilis to Produce Novel Benzoic Derivatives.

Microbial co-culture simulates the natural ecosystem through the combination of artificial microbes. This approach has been widely applied in the study of activating silent genes to reveal novel secondary metabolites. However, there are still challenges in determining the biosynthetic pathways. In this study, the effects of microbial co-culture on the morphology of the microbes were verified by the morphological observation. Subsequently, through the strategy combining substrate feeding, stable isotope labeling, and gene expression analysis, the biosynthetic pathways of five benzoic acid derivatives N1-N4 and N7 were demonstrated: the secondary metabolite 10-deoxygerfelin of A. sydowii acted as an inducer to induce B. subtilis to produce benzoic acid, which was further converted into 3-OH-benzoic acid by A. sydowii. Subsequently, A. sydowii used 3-OH-benzoic acid as the substrate to synthesize the new compound N2, and then N1, N3, N4, and N7 were biosynthesized upon the upregulation of hydrolase, hydroxylase, and acyltransferase during co-culture. The plate zone analysis suggested that the biosynthesis of the newly induced compounds N1-N4 was mainly attributed to A. sydowii, and both A. sydowii and B. subtilis were indispensable for the biosynthesis of N7. This study provides an important basis for a better understanding of the interactions among microorganisms, providing new ideas for studying the biosynthetic pathways of the newly induced secondary metabolites in co-culture.

Globally, tree fecundity exceeds productivity gradients.

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250-fold increase in seed abundance from cold-dry to warm-wet climates, driven primarily by a 100-fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics.

Tree diversity regulates forest pest invasion.

Nonnative pests often cause cascading ecological impacts, leading to detrimental socioeconomic consequences; however, how plant diversity may influence insect and disease invasions remains unclear. High species diversity in host communities may promote pest invasions by providing more niches (i.e., facilitation), but it can also diminish invasion success because low host dominance may make it more difficult for pests to establish (i.e., dilution). Most studies to date have focused on small-scale, experimental, or individual pest/disease species, while large-scale empirical studies, especially in natural ecosystems, are extremely rare. Using subcontinental-level data, we examined the role of tree diversity on pest invasion across the conterminous United States and found that the tree-pest diversity relationships are hump-shaped. Pest diversity increases with tree diversity at low tree diversity (because of facilitation or amplification) and is reduced at higher tree diversity (as a result of dilution). Thus, tree diversity likely regulates forest pest invasion through both facilitation and dilution that operate simultaneously, but their relative strengths vary with overall diversity. Our findings suggest the role of native species diversity in regulating nonnative pest invasions.

Worldwide effects of non-native species on species-area relationships.

Non-native species have invaded most parts of the world, and the invasion process is expected to continue and accelerate. Because many invading non-native species are likely to become permanent inhabitants, future consideration of species-area relationships (SARs) should account for non-native species, either separately or jointly with native species. If non-native species occupy unused niches and space in invaded areas and extinction rate of native species remains low (especially for plants), the resultant SARs (with both native and non-native species) will likely be stronger. We used published and newly compiled data (35 data sets worldwide) to examine how species invasions affect SARs across selected taxonomic groups and diverse ecosystems around the world. We first examined the SARs for native, non-native, and all species. We then investigated with linear regression analyses and paired or unpaired t tests how degree of invasion (proportion of non-native species) affected postinvasion SARs. Postinvasion SARs for all species (native plus non-native) became significantly stronger as degree of invasion increased (r2 = 0.31, p = 0.0006), thus, reshaping SARs worldwide. Overall, native species still showed stronger and less variable SARs. Also, slopes for native species were steeper than for non-native species (0.298 vs. 0.153). There were some differences among non-native taxonomic groups in filling new niches (especially for birds) and between islands and mainland ecosystems. We also found evidence that invasions may increase equilibrial diversity. Study of such changing species-area curves may help determine the probability of future invasions and have practical implications for conservation.

Efectos Globales de las Especies No Nativas sobre las Relaciones Especie-Área Resumen Las especies no nativas han invadido la mayor parte del mundo y se espera que el proceso de invasión continúe y se acelere. Ya que muchas especies invasoras no nativas probablemente se conviertan en habitantes permanentes, la consideración a futuro de las relaciones especie-área (REA) debería considerar a las especies no nativas, ya sea por separado o en conjunto con las especies nativas. Si las especies no nativas ocupan nichos sin usar y el espacio en las áreas invadidas y la tasa de extinción de las especies nativas permanecen bajas (especialmente para las plantas), las REA resultantes (tanto con las especies nativas como las no nativas) probablemente sean más fuertes. Usamos datos publicados y recientemente compilados (35 conjuntos de datos mundiales) para examinar cómo las invasiones de especies afectan a las REA en grupos taxonómicos selectos y en diversos ecosistemas en todo el mundo. Primero examinamos las REA para todas las especies, así como para las nativas y las no nativas. Después investigamos con análisis de regresión lineal y pruebas t emparejadas o no emparejadas cómo afectó el grado de invasión (proporción de la especie no nativa) a las REA post-invasión. Las REA post-invasión para todas las especies (nativas más no nativas) se volvieron significativamente más fuertes conforme incrementó el grado de invasión (r2 = 0.31, p = 0.0006), remodelando así las REA en todo el mundo. En general, las especies nativas todavía mostraron REA más fuertes y menos variables. De igual manera, las pendientes de las especies nativas fueron más pronunciadas para las especies no nativas (0.298 vs. 0.153). Hubo algunas diferencias entre los grupos taxonómicos no nativos al llenar nichos nuevos (especialmente para las aves) y entre las islas y los ecosistemas de tierra firme. También encontramos evidencias de que las invasiones pueden incrementar la diversidad equilibrada. El estudio de dichas curvas cambiantes de relación especie-área podría ayudar a determinar la probabilidad de las futuras invasiones y tener implicaciones prácticas para la conservación.

Biodiversity increases the resistance of ecosystem productivity to climate extremes.

It remains unclear whether biodiversity buffers ecosystems against climate extremes, which are becoming increasingly frequent worldwide. Early results suggested that the ecosystem productivity of diverse grassland plant communities was more resistant, changing less during drought, and more resilient, recovering more quickly after drought, than that of depauperate communities. However, subsequent experimental tests produced mixed results. Here we use data from 46 experiments that manipulated grassland plant diversity to test whether biodiversity provides resistance during and resilience after climate events. We show that biodiversity increased ecosystem resistance for a broad range of climate events, including wet or dry, moderate or extreme, and brief or prolonged events. Across all studies and climate events, the productivity of low-diversity communities with one or two species changed by approximately 50% during climate events, whereas that of high-diversity communities with 16-32 species was more resistant, changing by only approximately 25%. By a year after each climate event, ecosystem productivity had often fully recovered, or overshot, normal levels of productivity in both high- and low-diversity communities, leading to no detectable dependence of ecosystem resilience on biodiversity. Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events. Anthropogenic environmental changes that drive biodiversity loss thus seem likely to decrease ecosystem stability, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity to climate events.

Alterations in leaf nitrogen metabolism indicated the structural changes of subtropical forest by canopy addition of nitrogen.

Globally, nitrogen deposition increment has caused forest structural changes due to imbalanced plant nitrogen metabolism and subsequent carbon assimilation. Here, a 2 consecutive-year experiment was conducted to reveal the effects of canopy addition of nitrogen (CAN) on nitrogen absorption, assimilation, and allocation in leaves of three subtropical forest woody species (Castanea henryi, Ardisia quinquegona, and Blastus cochinchinensis). We hypothesized that CAN altered leaf nitrogen absorption, assimilation and partitioning of different plants in different ways in subtropical forest. It shows that CAN increased maximum photosynthetic rate (Amax), photosynthetic nitrogen use efficiency (PNUE), and metabolic protein content of the two understory species A. quinquegona and B. cochinchinensis. By contrary, for the overstory species, C. henryi, Amax, PNUE, and metabolic protein content were significantly reduced in response to CAN. We found that changes in leaf nitrogen metabolism were mainly due to the differences in enzyme (e.g. Ribulose-1,5-bisphosphate carboxylase, nitrate reductase, nitrite reductase and glutamine synthetase) activities under CAN treatment. Our results indicated that C. henryi may be more susceptible to CAN treatment, and both A. quinquegona and B. cochinchinensis could better adapt to CAN treatment but in different ways. Our findings may partially explain the ongoing degradation of subtropical forest into a community dominated by small trees and shrubs in recent decades. It is possible that persistent high levels of atmospheric nitrogen deposition will lead to the steady replacement of dominant woody species in this subtropical forest.

A unified approach for quantifying invasibility and degree of invasion.

Habitat invasibility is a central focus of invasion biology, with implications for basic ecological patterns and processes and for effective invasion management. "Invasibility" is, however, one of the most elusive metrics and misused terms in ecology. Empirical studies and meta-analyses of invasibility have produced inconsistent and even conflicting results. This lack of consistency, and subsequent difficulty in making broad cross-habitat comparisons, stem in part from (1) the indiscriminant use of a closely related, but fundamentally different concept, that of degree of invasion (DI) or level of invasion; and (2) the lack of common invasibility metrics, as illustrated by our review of all invasibility-related papers published in 2013. To facilitate both cross-habitat comparison and more robust ecological generalizations, we clarify the definitions of invasibility and DI, and for the first time propose a common metric for quantifying invasibility based on a habitat's resource availability as inferred from relative resident species richness and biomass. We demonstrate the feasibility of our metric using empirical data collected from 2475 plots from three forest ecosystems in the eastern United States. We also propose a similar metric for DI. Our unified, resource-based metrics are scaled from 0 to 1, facilitating cross-habitat comparisons. Our proposed metrics clearly distinguish invasibility and DI from each other, which will help to (1) advance invasion ecology by allowing more robust testing of generalizations and (2) facilitate more effective invasive species control and management.

Using ecological memory as an indicator to monitor the ecological restoration of four forest plantations in subtropical China.

A large area of plantations has been established worldwide and especially in China. Evaluating the restoration status of these plantations is essential for their long-term management. Based on our previous work, we used an ecological memory (EM) approach to evaluate four 26-year-old plantations that represent four common kinds of plantations in subtropical China, i.e., mixed broad-leaved plantation (MBP), mixed coniferous plantation (MCP), eucalyptus plantation (EP), and mixed legume plantation (MLP). Comparing them with the regional climax community, i.e., monsoon evergreen broad-leaved forest (BF), all four plantations accumulated nearly the same pattern of EM during succession. EM was >50 % for soil minerals, light conditions, soil age, soil animals, and soil microbes. EM was about 25 % for soil pollen and 10 % for birds, soil seed bank, and plant species. The total EM value of the four plantations ranged from 50.96 to 52.54, which indicated that all four plantations were in the regional, natural trajectory of succession and between the early and medium successional stages. The results indicated that natural succession processes are unlikely to be accelerated by planting late-stage tree species without sufficient EM. The results also demonstrated that all four plantations were in positive successional trajectories, and the positive succession dynamics were greater in the MLP and MCP. We suggest that the entire natural succession trajectory be used to evaluate the restoration of a site and that the ultimate restoration target be divided into several milestones along the reference trajectory to monitor progress. Forest restoration may be accelerated by starting with a minimum dynamic unit supporting sufficient EM.

Effect of urbanization on the structure and functional traits of remnant subtropical evergreen broad-leaved forests in South China.

We investigated the effects of major environmental drivers associated with urbanization on species diversity and plant functional traits (PFTs) in the remnant subtropical evergreen broad-leaved forests in Metropolitan Guangzhou (Guangdong, China). Twenty environmental factors including topography, light, and soil properties were used to quantify the effects of urbanization. Vegetation data and soil properties were collected from 30 400-m(2) plots at 6 study sites in urban and rural areas. The difference of plant species diversity and PFTs of remnant forests between urban and rural areas were analyzed. To discern the complex relationships, multivariate statistical analyses (e.g., canonical correspondence analysis and regression analysis) were employed. Pioneer species and stress-tolerant species can survive and vigorously establish their population dominance in the urban environment. The native herb diversity was lower in urban forests than in rural forests. Urban forests tend to prefer the species with Mesophanerophyte life form. In contrast, species in rural forests possessed Chamaephyte and Nanophanerophyte life forms and gravity/clonal growth dispersal mode. Soil pH and soil nutrients (K, Na, and TN) were positively related to herb diversity, while soil heavy metal concentrations (Cu) were negatively correlated with herb diversity. The herb plant species diversity declines and the species in the remnant forests usually have stress-tolerant functional traits in response to urbanization. The factors related to urbanization such as soil acidification, nutrient leaching, and heavy metal pollution were important in controlling the plant diversity in the forests along the urban-rural gradients. Urbanization affects the structure and functional traits of remnant subtropical evergreen broad-leaved forests.

Does regional species diversity resist biotic invasions?

The role of regional species diversity in large-scale species invasions has been largely controversial. On the one hand, it has been proposed that diversity may facilitate invasion ("diversity begets diversity") because regions with higher diversity may indicate favorable conditions for many more species. On the other hand, high diversity may indicate high levels of niche occupation, thus making it more difficult for new species to invade. In the past, invasion biologists have evaluated how regional native and exotic richness are related. Here, we test whether the range size of exotic species may be constrained by regional native richness using plant data from three continental regions in the Northern Hemisphere, i.e., Europe, Eastern Asia, and North America. We found that regional native plant diversity is inversely related to the range size of exotic species. This result may be due to stronger species interactions such as competition in species-rich habitats that limit the establishment and spread of exotic species.

Integrating gradient with scale in ecological and evolutionary studies.

Gradient and scale are two key concepts in ecology and evolution that are closely related but inherently distinct. While scale commonly refers to the dimensional space of a specific ecological/evolutionary (eco-evo) issue, gradient measures the range of a given variable. Gradient and scale can jointly and interactively influence eco-evo patterns. Extensive previous research investigated how changing scales may affect the observation and interpretation of eco-evo patterns; however, relatively little attention has been paid to the role of changing gradients. Here, synthesizing recent research progress, we suggest that the role of scale in the emergence of ecological patterns should be evaluated in conjunction with considering the underlying environmental gradients. This is important because, in most studies, the range of the gradient is often part of its full potential range. The difference between sampled (partial) versus potential (full) environmental gradients may profoundly impact observed eco-evo patterns and alter scale-gradient relationships. Based on observations from both field and experimental studies, we illustrate the underlying features of gradients and how they may affect observed patterns, along with the linkages of these features to scales. Since sampled gradients often do not cover their full potential ranges, we discuss how the breadth and the starting and ending positions of key gradients may affect research design and data interpretation. We then outline potential approaches and related perspectives to better integrate gradient with scale in future studies.

Combinational application of the natural products 1-deoxynojirimycin and morin ameliorates insulin resistance and lipid accumulation in prediabetic mice.

BACKGROUND: Prediabetes, a stage characterized by chronic inflammation, obesity and insulin resistance. Morin and 1-deoxynojirimycin (DNJ) are natural flavonoids and alkaloids extracted from Morus nigra L., exhibiting anti-hyperglycemic efficacy. However, the benefits of DNJ are shadowed by the adverse events, and the mechanism of morin in anti-diabetes remains under investigation. PURPOSE: In this study, the combinational efficacy and mechanisms of DNJ and morin in ameliorating insulin resistance and pre-diabetes were investigated. METHODS: The mice model with prediabetes and Alpha mouse liver-12 (AML-12) cell model with insulin resistance were established. The anti-prediabetic efficacy of the drug combination was determined via analyzing the blood glucose, lipid profiles and inflammatory factors. The application of network pharmacology provided guidance for the research mechanism. RESULTS: In our study, the intervention of morin ameliorated the insulin resistance via activating the Peroxisome proliferator-activated receptor γ (PPARγ). However, PPARγ activation leaded to the lipid accumulation in prediabetic mice. The combination of 5 mg/kg dose of DNJ and 25 mg/kg morin effectively hindered the progression of T2DM by 87.56%, which was achieved via inhibition of Suppressors of cytokine signaling 3 (SOCS3) and promotion of PPARγ as well as SOCS2 expression. Furthermore, this treatment exhibited notable capabilities in combating dyslipidemia and adipogenesis, achieved by suppressing the Cluster of differentiation 36/ Sterol-regulatory element binding proteins-1/ Fatty acid synthetase (CD36/Serbp1/Fas) signaling. CONCLUSION: This research confirmed that the drug combination of DNJ and morin in ameliorating insulin resistance and lipid accumulation, and revealed the potential mechanisms. In summary, the combination of DNJ and morin is an underlying alternative pharmaceutical composition in T2DM prevention.

Masting is uncommon in trees that depend on mutualist dispersers in the context of global climate and fertility gradients.

The benefits of masting (volatile, quasi-synchronous seed production at lagged intervals) include satiation of seed predators, but these benefits come with a cost to mutualist pollen and seed dispersers. If the evolution of masting represents a balance between these benefits and costs, we expect mast avoidance in species that are heavily reliant on mutualist dispersers. These effects play out in the context of variable climate and site fertility among species that vary widely in nutrient demand. Meta-analyses of published data have focused on variation at the population scale, thus omitting periodicity within trees and synchronicity between trees. From raw data on 12 million tree-years worldwide, we quantified three components of masting that have not previously been analysed together: (i) volatility, defined as the frequency-weighted year-to-year variation; (ii) periodicity, representing the lag between high-seed years; and (iii) synchronicity, indicating the tree-to-tree correlation. Results show that mast avoidance (low volatility and low synchronicity) by species dependent on mutualist dispersers explains more variation than any other effect. Nutrient-demanding species have low volatility, and species that are most common on nutrient-rich and warm/wet sites exhibit short periods. The prevalence of masting in cold/dry sites coincides with climatic conditions where dependence on vertebrate dispersers is less common than in the wet tropics. Mutualist dispersers neutralize the benefits of masting for predator satiation, further balancing the effects of climate, site fertility and nutrient demands.

Incorporating latitudinal and central-marginal trends in assessing genetic variation across species ranges.

The genetic variation across a species' range is an important factor in speciation and conservation, yet searching for general patterns and underlying causes remains challenging. While the majority of comparisons between central and marginal populations have revealed a general central-marginal (C-M) decline in genetic diversity, others show no clear pattern. Similarly, most latitudinal studies (although much fewer, especially those conducted rangewide) also showed latitudinal trends in genetic variation. To date, the C-M and latitudinal patterns have often been examined independently and have rarely been considered together when accounting for the observed genetic variation across species ranges. Here, in the light of the most recent findings, I show how latitude might be responsible for some of the deviations from the general C-M trends in genetic diversity, and vice versa. In the future, integrating latitude and range geometry with climate-induced species migration would offer important insights into conservation prioritization across species ranges.

Scale dependency in native-exotic richness relationships revisited.

In their seminal paper, Shea and Chesson (Trends in Ecology & Evolution, 2002, 17, 170) developed a highly cited model (S&C model) showing scale dependency in the native-exotic richness relationships. Two decades later, extensive additional data have been accumulated, leading to new findings and insights. Accordingly, two updates were made here to the original S&C model: (1) changing the "negative" richness relationship between natives and exotics to "non-consistent" or "non-significant"; and (2) modifying the original diagram to correctly represent native and exotic species richness and their correlations across both small and large scales.

The ecology of COVID-19 and related environmental and sustainability issues.

Around the globe, human behavior and ecosystem health have been extensively and sometimes severely affected by the unprecedented COVID-19 pandemic. Most efforts to study these complex and heterogenous effects to date have focused on public health and economics. Some studies have evaluated the pandemic's influences on the environment, but often on a single aspect such as air or water pollution. The related research opportunities are relatively rare, and the approaches are unique in multiple aspects and mostly retrospective. Here, we focus on the diverse research opportunities in disease ecology and ecosystem sustainability related to the (intermittent) lockdowns that drastically reduced human activities. We discuss several key knowledge gaps and questions to address amid the ongoing pandemic. In principle, the common knowledge accumulated from invasion biology could also be effectively applied to COVID-19, and the findings could offer much-needed information for future pandemic prevention and management.

Ameliorating Effect of the Total Flavonoids of Morus nigra L. on Prediabetic Mice Based on Regulation of Inflammation and Insulin Sensitization.

Prediabetes is a critical stage characterized by insulin resistance. Morus nigra L., an edible plant, is widely used in food and nutritive supplements and exhibits various pharmacological activities; however, its therapeutic effects and mechanisms on prediabetes have rarely been reported. In this research, the major components of total flavonoids of M. nigra L. (TFM) were identified, and TFM treatment was found to reduce prediabetes progressing to type 2 diabetes mellitus (T2DM) from 93.75 to 18.75%. The microbiota and next-generation sequencing combined with western blotting in vivo and in vitro demonstrated that TFM and its components ameliorated insulin resistance mediated by the suppressor of cytokine signaling and protein tyrosine phosphatase 1B, which benefited by maintaining intestinal homeostasis and restraining plasma levels of inflammatory factors. This study confirmed the T2DM prevention effect of TFM and revealed the underlying mechanism, setting the stage for the design of functional foods for diabetes prevention.