Species-rich Communities Research Articles

Energy reserves and gut microbiota of marine mussels under combined exposure to pathogens and predation risk

In recent years, environmental issues such as eutrophication have led to proliferation of pathogenic bacteria and deterioration of aquaculture environmental water quality. However, the impact of pathogenic bacteria on the mussel-predator food chain in the marine environment is not yet fully understood. In this experiment, mussels were cultured with crabs (Charybdis japonica) for 14 days. Then crabs were retained or removed and pathogenic bacteria (Vibrio alginolyticus) was added and mussels were cultured for 3 days. C. japonica and V. alginolyticus were used as two stressors to explore their effects on energy content and gut microbiota of Mytilus coruscus. The metabolic parameters (protein, carbohydrate and lipid contents) of the gills and digestive glands, and the gut microbiota of the mussels were measured. The study found that presence of predation risk significantly increased the content of protein but decreased carbohydrate and lipid contents in the gills at 14th day. After 17 days of exposure, the presence of predation risk significantly reduced protein content but significantly increased lipid content in gills of mussel. The protein content in digestive gland was significantly increased, but the lipid content was significantly decreased. The presence of predation risk and pathogens had interactive effect on the protein content in the digestive glands of mussels. The presence of V. alginolyticus and predation risk affected the community structure, species richness, and diversity of gut microbiota. The most abundant phyla noted were Bacteroidota, Proteobacteria, and Firmicutes, and the most abundant genus noted were Prevotella, Klebsiella and Dialister. Alpha diversity analysis and beta diversity analysis revealed that the presence of V. alginolyticus and predation risk altered the microbial community structure. V. alginolyticus plays a positive role in the harmful microbiota of gut microbiota. The proportion of Bacteroidota and Proteobacteria in intestinal bacteria increased significantly. Linear discriminant analysis effect size (LEfSe) showed that the biomarkers in each group are significantly different at the genus level. Significant correlations between metabolic parameters (protein content and carbohydrate content) and the level of KEGG function prediction (amino acid metabolism and carbohydrate metabolism) were observed in gills and digestive glands. This study highlights the priority of energy responses in mussels under dual predator-pathogen pressure, and also highlights the complexity of predator-pathogen interactions. A better understanding of their impact on the gut microbiota and health of marine mussels will help support the sustainability of mussel aquaculture production.

Intra-annual compositions and diversity variations of waterbird communities in China

Waterbirds are often used as indicators of wetland biodiversity and ecosystem health due to their sensitivity to environmental changes. However, most studies have focused on long-term variations of waterbird communities, while the intra-annual changes have rarely been investigated. Here, we analyzed the seasonal dynamics of compositions and the intra-annual variations of species richness and abundance of waterbird communities among the nine major river basins of China, and focused on the effects of different residential types and taxonomic groups on the diversity variations. In most of the nine basins, the waterbird communities in spring and autumn showed high similarity, while those in summer and winter were quite different. Such a seasonal cycle of species composition was caused by the seasonal migration of waterbirds. The season with higher species richness shifted from summer to winter as the latitude of the basin decreased within China, but almost all basins had the lowest community abundance in summer. This was because the variation of richness was directly influenced by the variation in species composition, but the variation of abundance was more influenced by the population size of different waterbird assemblages. Our results emphasized the importance of seasonal dynamics of waterbird communities to the understanding of their migration patterns, and highlighted the impact of different waterbird assemblages on intra-annual community variations. Additionally, we also noted the potential effects of population size and behaviors at different parts of the waterbird life circle on the observations of them. The information gathered in this study will provide guidance for the conservation of waterbird species and their habitats.

Achieving structural heterogeneity and high multi-taxon biodiversity in managed forest ecosystems: a European review

AbstractThe European Biodiversity Strategy has set the key goal to maintain and promote biodiversity. Managed forests here play a key role, as they are among the most diverse ecosystems. To create biodiversity rich managed forest landscapes, we need a deep understanding on how management affects forest structure and subsequently habitat quality on the local and landscape level. However, to date a confusingly large amount of different terms for various management systems exist and it remains unclear how forest structure and composition affected by specific management systems affect biodiversity. Here, we first aim to clarify forest management systems terminology. Second, we link existing management systems with forest structure and review at European level how these structures affect local α-, as well as landscape-scale β- and γ-biodiversity. We found that research and derived management guidelines have a strong focus on local forest stand heterogeneity and related α-diversity, while ignoring the importance of landscape-scale heterogeneity and therefore β- and γ-diversity. Instead of promoting one management system as an all-in-one-solution, a diversity of different forest management systems seems the most promising way to create biodiversity rich forest landscapes. We finally discuss how a combination of different management systems might help to create structurally rich forest habitats and landscapes, simulating different successional stages and promoting species rich communities.

Decrease due to pollution in the rhizosphere microbial diversity can be amended by supplementation from adapted plants of another species

Manipulating the rhizosphere microbiome to enhance plant stress tolerance is an environmentally friendly technology and a renewable resource to restore degraded environments. Here we suggest a sustainable bioremediation strategy on the example of Stebnyk mine tailings storage. We consider Salicornia europaea rhizosphere community, and the ability of the phytoremediation plant Salix viminalis to recruit its beneficial microbiome to mediate the pollution stress at the Stebnyk mine tailings storage. The tailings contain large amounts of brine salts and heavy metals that contaminate the ground water and surrounding areas, changing soil biogeochemistry and causing increased erosion. The species richness of the endophytic bacterial community of S. viminalis roots was assessed based on observed OTUs, Shannon-InvSimpson, and evenness index. Our results obtained using the plant-based enrichment strategy show that biodiversity was decreased across the contamination zones and that S. europaea supplementation significantly increased the species richness. Our results also indicate that the number of dominating bacteria was not changed across zones in both S. europaea-treated and untreated bacterial populations, and that the decrease in richness was mainly caused by the low abundant bacterial OTUs. The importance of selecting the bioremediation strains that are likely to harbor a reservoir of genetic traits that aid in bioremediation function from the target environment is discussed

Reduction of damage by the exotic invasive conifer seed bug Leptoglossus occidentalis in mixed pine-birch plantations: A case of biotic resistance

The number of invasive non-native pests is increasing rapidly in forests as a result of global change. It is therefore important to prevent their damage in order to preserve the integrity of forest ecosystems and the associated services. According to the biotic resistance hypothesis, species-rich communities are less likely to be invaded. The associational resistance hypothesis states that insect herbivores are more likely to colonise and exploit plants surrounded by conspecific neighbours than heterospecific, non-host plant species. More diverse forests would therefore be less damaged by non-native pests than tree monocultures. We tested these hypotheses by comparing the damage caused to seeds by the western conifer bug Leptoglossus occidentalis, an invasive insect native to North America, in plots of pure maritime pine and mixed plots of maritime pine and birch. These plots were in two tree diversity experiments in Europe. Mixed pine plots differed in terms of pine density (1250 versus 625 pines/ha), proportion of pine and birch (25 %, 50 %, 75 %) and spatial mixing pattern (aggregated versus dispersed). We sampled 635 cones in 37 plots. Overall, the proportion of seeds damaged by the invasive bug was significantly lower in mixed plots than in pure pine plots at both experimental sites. There was no significant effect of pine density or relative proportion in the mixtures on seed damage. Aggregated pines in the mixed plots were significantly more damaged than dispersed pines, suggesting that bugs may have done less damage when they had more difficulty locating their host trees. This is consistent with the hypothesis of lower plant apparency. These results support the view that forest plantations of mixed species, which are known to be less vulnerable to attack by native insects, may also be more resistant to infestation by exotic insects. Row-wise, intimate mixtures of two species represent a promising option for designing tree plantations that are more resistant and easier to manage.

Topography and soil variables drive the plant community distribution pattern and species richness in the Arjo-Diga forest in western Ethiopia.

Understanding plant community characteristics, distributions, and environmental relationships is crucial for sustainable forest management. Thus, this study examined the relationships between plant community composition and topographic and soil variables within the Arjo-Diga forest. Vegetation data were collected from 72 nested plots (30 × 30 m2 and 2 × 2 m2) systematically laid along nine transects spaced 300 to 700 m apart. Environmental variables, including soil properties and anthropogenic disturbance, were recorded within each main plot. Agglomerative hierarchical cluster analysis and canonical correspondence analysis (CCA) using R software were employed to identify distinct plant community types and examine their relationships with environmental factors. The Shannon‒Wiener diversity index was calculated to quantify and compare species diversity among the identified community types. The analysis revealed five distinct plant community types: 1: Maesa lanceolata-Ehretia cymosa, 2: Trichilia dregeana-Flacourtia indica, 3: Acacia abyssinica-Millettia ferruginea, 4: Combretum collinum-Croton macrostachyus, and 5: Terminalia macroptera-Piliostigma thonningii. The CCA results highlighted the significant influence (p < 0.05) of altitude, CEC, TN, and disturbance on species distribution and plant community formation. The findings indicate that variation in plant communities is closely associated with altitude, TN, and CEC, as well as with disturbance factors such as human interventions, with elevation being the most influential factor. Based on these findings, it is recommended that conservation plans consider the effects of human interventions to address the challenges in conserving forests in the future. Additionally, further research efforts should focus on mitigating disturbance factors and understanding the environmental variables that affect forests to improve their protection.

A century of wild bee sampling: historical data and neural network analysis reveal ecological traits associated with species loss.

We analysed the wild bee community sampled from 1921 to 2018 at a nature preserve in southern Michigan, USA, to study long-term community shifts in a protected area. During an intensive survey in 1972 and 1973, Francis C. Evans detected 135 bee species. In the most recent intensive surveys conducted in 2017 and 2018, we recorded 90 species. Only 58 species were recorded in both sampling periods, indicating a significant shift in the bee community. We found that the bee community diversity, species richness and evenness were all lower in recent samples. Additionally, 64% of the more common species exhibited a more than 30% decline in relative abundance. Neural network analysis of species traits revealed that extirpation from the reserve was most likely for oligolectic ground-nesting bees and kleptoparasitic bees, whereas polylectic cavity-nesting bees were more likely to persist. Having longer phenological ranges also increased the chance of persistence in polylectic species. Further analysis suggests a climate response as bees in the contemporary sampling period had a more southerly overall distribution compared to the historic community. Results exhibit the utility of both long-term data and machine learning in disentangling complex indicators of bee population trajectories.

Multiple cropping effectively increases soil bacterial diversity, community abundance and soil fertility of paddy fields

BackgroundCrop diversification is considered as an imperative approach for synchronizing the plant nutrient demands and soil nutrient availability. Taking two or more crops from the same field in one year is considered as multiple cropping. It improves the diversity and abundance of soil microbes, thereby improving the growth and yield of crops. Therefore, the present study was conducted to explore the effects of different multiple winter cropping on soil microbial communities in paddy fields. In this study, eight rice cropping patterns from two multiple cropping systems with three different winter crops, including Chinese milk vetch (CMV), rape, and wheat were selected. The effects of different multiple winter cropping on soil microbial abundance, community structure, and diversity in paddy fields were studied by 16 S rRNA high-throughput sequencing and real-time fluorescence quantitative polymerase chain reaction (PCR).ResultsThe results showed that different multiple winter cropping increased the operational taxonomic units (OTUs), species richness, and community richness index of the bacterial community in 0 ~ 20 cm soil layer. Moreover, soil physical and chemical properties of different multiple cropping patterns also affected the diversity and abundance of microbial bacterial communities. The multiple cropping increased soil potassium and nitrogen content, which significantly affected the diversity and abundance of bacterial communities, and it also increased the overall paddy yield. Moreover, different winter cropping changed the population distribution of microorganisms, and Proteobacteria, Acidobacteria, Nitrospira, and Chloroflexi were identified as the most dominant groups. Multiple winter cropping, especially rape-early rice-late rice (TR) andChinese milk vetch- early rice-late rice (TC) enhanced the abundance of Proteobacteria, Acidobacteria, and Actinobacteria and decreased the relative abundance of Verrucomicrobia and Euryarchaeota.ConclusionIn conclusion, winter cropping of Chinese milk vetch and rape were beneficial to improve the soil fertility, bacteria diversity, abundance and rice yield.

Alpine wetlands degradation leads to soil nutrient imbalances that affect plant growth and microbial diversity

Alpine wetlands degrade rapidly due to climate change and human activities. Studying degradation effects on flora, soil, and microbes, and their mechanisms, can aid wetland management and global carbon dynamic insights. Here, we conducted transect surveys across various levels of degradation in the Qinghai-Tibet Plateau, ranging from non-degraded to severely degraded alpine wetlands. Severe degradation reduced aboveground biomass by 72.5%. As degradation intensified, the abundance of high-quality forage plants, especially Cyperaceae, gradually declined. Degradation resulted in soil nutrient deficiencies and stoichiometric imbalances, which significantly affected plant growth and soil microbial diversity. These changes ultimately led to a decline in carbon sequestration. The diversity of microbial and plant communities’ response to degradation aligned with the “intermediate interference hypothesis.” The altered bacterial community composition, which favors oligotrophic dominance, and its nonlinear response to soil stoichiometry and pH, could explain the maintenance of diversity and species richness of microbial communities under intermediate disturbance.

Relationship between potentially toxic elements and macrophyte communities in the Sava river

Freshwater ecosystems are at significant risk of contamination by potentially toxic elements (PTEs) due to their high inherent toxicity, their persistence in the environment and their tendency to bioaccumulate in sediments and living organisms. We investigated aquatic macrophyte communities and the concentrations of As, Cu, Cd, Cr, Pb, Zn, Ni and Fe in water and sediment samples to identify a pollution pattern along the Sava River and to investigate the potential impact of these PTEs on the diversity and structure of macrophyte communities. The study, which covered 945 km of the Sava River, showed a downstream increase in sediment concentrations of the analyzed elements. Both species richness and alpha diversity of macrophyte communities also generally increase downstream. Ordinary and partial Mantel tests indicate that macrophyte communities are significantly correlated with sediment chemistry, but only weakly correlated with water chemistry. In the lowland regions (downstream), beta diversity decreases successively, which can be attributed to an increasing similarity of environmental conditions at downstream sites. Species richness is relatively low at sites with low concentrations of Cr, Cd, Fe, and Cu in the sediment. However, species richness increases to a certain extent with increasing element concentrations; as element concentrations increase further, species richness decreases, probably as a result of increased toxicity. Some species that are generally more tolerant to high concentrations of PTEs are: Ceratophyllum demersum, Iris pseudacorus, Najas marina, Butomus umbellatus, Vallisneria spiralis, Potamogeton gramineus and Bolboschoenus maritimus maritimus. Potamogeton perfoliatus and the moss species Cinclidotus fontinaloides and Fontinalis antipyretica have narrow ecological amplitudes in relation to the concentrations of PTEs in the sediment.

Phytoremediation of technogenically disturbed soils of coal mines

The use of joint planting of tree species with different life strategies, annual growth rates, but with a complementary reaction to co-growth in reclamation sites makes it possible to more effectively use ecological niches and ensure the formation of species-rich forest communities with higher biological productivity. At each age stage of planting, a certain category of woody plants "works" on carbon accumulation, which generally provides an increased deposition effect compared to single-species plantations. Modern recommendations on forest reclamation are focused on the creation of monocultures that are insufficiently stable, do not create a nature-like structure of plant communities and are not sustainable for a long period of time. Currently, technologies have been developed taking into account the sustainability of forest plantations on landfills.

Containing alien plants in coastal dunes: Evidence from a soil manipulation experiment

Biological invasion is recognised as one of the major threats to biodiversity, particularly in disturbance-prone ecosystems such as costal dunes. Many studies have associated alien plant invasion of dune ecosystem to human disturbances, but less is known about the role of soil properties in invasion after disturbance. Soil properties are crucial filters during plant succession and soil-related changes in the initial stage of species colonization might shape the final success of the invaders.We performed a manipulative experiment aimed at elucidating the effects of soil properties on plant colonization processes in highly invaded dune systems, as a proxy for plausible management actions to curb the success of exotic plant species over native ones, which was measured through species richness and abundance.In a barrier island of the Marano and Grado lagoon, Northern Adriatic Sea, we mechanically removed all the native and alien vegetation present in the back dune (also known as secondary dune), triggering a new ecological succession and further altered, for the following three months, soil properties by adding salt, nitrogen, and organic matter in a full factorial design with randomized blocks.The soil treatments reduced the overall species richness and abundance of alien plants. Further, soil treatment interactions strongly shaped community evenness and species richness. Soil salinity had a positive effect on native cover while decreasing the overall number of alien species, especially in soil with added organic matter.Our findings suggest that soil salinity, and its interplay with organic matter, might significantly reduce the initial success of alien species propagule pressure (i.e. alien plant germination), with likely implications for the trajectories of future plant communities. This study highlights that alien plant containment should be focused on early stages of succession, giving new perspective on future environmental management actions for dune restoration and conservation.

Bioindication potentials of the grass stand and soil macrofauna for assessing the level of anthropogenic transformation of an urban park are complementary

Changes in the environment induced by anthropogenic impact or natural stressors are subject to bioindication. Most often, the anthropogenic stressors are the main object of bioindication research. Hemeroby and naturalness are considered as indicators of the level of anthropogenic transformation of ecosystems. Hemeroby is frequently used to assess disturbances in different types of vegetation. However, this concept has rarely been used to assess the impact on animals. According to the method of indicator values, species richness of a community is a marker of bioindication potential. The article compares the patterns of response of species richness of soil macrofauna and herbaceous cover communities in a city park, taking into account gradients of environmental factors, naturalness, and hemeroby. Within the study area, test plots were located. Soil macrofauna samples were taken at 105 points in each of the test sites, and soil hardness, electrical conductivity and soil temperature, litter height, and grass cover height were also measured. A geobotanical description of the vegetation cover was made within each plot. In the survey plots, 7.6 ± 3.0 plant species were found in the herbaceous layer. In soil samples, 6.8 ± 2.9 species of macrofauna were found. With an increase in the number of plant species in the herbaceous layer, the number of soil macrofauna species showed a downward trend. An increase in the number of soil macrofauna species is accompanied by a decrease in both naturalness and hemeroby of the plant community. The naturalness index does not depend on the number of plant species, but the largest number of plant species was observed under conditions of naturalness level from 0 to 1. With an increase in hemeroby, the number of plant species increases, although this relationship also has a nonlinear component. The largest number of plant species is observed at hemeroby levels from 45 to 65. Environmental factors and indicators of hemeroby and naturalness were able to explain 27% of the variation in the number of soil macrofauna species. Humidity regime and continentality did not affect the number of species. Increased variability in moisture conditions, carbonate content, and indicators of frost and cryoclimate contributed to an increase in the number of invertebrate species. Increases in acidity, mineral salts, nitrates, and soil aeration had a negative impact on the number of soil macrofauna species. Soil properties were able to explain 21% of the variation in the number of soil macrofauna species. Environmental factors and indicators of hemeroby and naturalness were able to explain 72% of the variation in the number of herbaceous plant species. Increases in moisture, acidity, mineralization, thermocline, and cryoclimate indicators had a negative impact on the number of plant species. Biological indicators can be used to assess complex environmental factors that are difficult to measure using instrumental methods. Bioindicators are also used to assess the level of anthropogenic transformation of ecosystems. The key concepts for solving this problem are the naturalness and hemeroby of plant communities, which are used as markers of ecosystem disturbance in general. Vegetation cover as a source of bioindication information can provide a biased assessment of the level of anthropogenic transformation due to its greater sensitivity to certain types of anthropogenic pressure. The potential of soil animals as a source of information on the level of anthropogenic transformation in the urban environment is quite significant. Species richness is a marker of the potential ability of a plant or animal community to provide reliable bioindication information. The bioindication complementarity of animal and plant communities is that the highest species richness of soil macrofauna is observed at a relatively low level of species richness of plant communities. Therefore, soil macrofauna can complement and clarify estimates of the level of anthropogenic transformation made using plant communities or can be an independent source of information for such estimates.

Species richness and evenness of European bird communities show differentiated responses to measures of productivity.

Understanding patterns of species diversity is crucial for ecological research and conservation, and this understanding may be improved by studying patterns in the two components of species diversity, species richness and evenness of abundance of species. Variation in species richness and evenness has previously been linked to variation in total abundance of communities as well as productivity gradients. Exploring both components of species diversity is essential because these components could be unrelated or driven by different mechanisms. The aim of this study was to investigate the relationship between species richness and evenness in European bird communities along an extensive latitudinal gradient. We examined their relationships with latitude and Net Primary Productivity, which determines energy and matter availability for heterotrophs, as well as their responses to territory densities (i.e. the number of territories per area) and community biomass (i.e. the bird biomass per area). We applied a multivariate Poisson log-normal distribution to unique long-term, high-quality time-series data, allowing us to estimate species richness of the community as well as the variance of this distribution, which acts as an inverse measure of evenness. Evenness in the distribution of abundance of species in the community was independent of species richness. Species richness increased with increasing community biomass, as well as with increasing density. Since both measures of abundance were explained by NPP, species richness was partially explained by energy-diversity theory (i.e. the more energy, the more species sustained by the ecosystem). However, species richness did not increase linearly with NPP but rather showed a unimodal relationship. Evenness was not explained either by productivity nor by any of the aspects of community abundance. This study highlights the importance of considering both richness and evenness to gain a better understanding of variation in species diversity. We encourage the study of both components of species diversity in future studies, as well as use of simulation studies to verify observed patterns between richness and evenness.

Changes in plant diversity of European lowland forests: Increased homogenization and expansion of shade-tolerant trees

European lowland forests have undergone significant transformations over the past century due to increased canopy closure, eutrophication and plant invasions. The new millennium has brought plant invasions, alien fungal pathogens, and extreme weather conditions, all contributing to forest diebacks. However, the response of plant diversity remains poorly understood. We examined changes in understorey vegetation following a decade (2012–2021) of severe drought in four temperate lowland forest types (dominated by oaks, hornbeams, ashes, and willows) to understand how water availability, canopy openness, and alien fungal pathogens altered diversity in interaction with climate change. Following an exceptionally warm decade, the vegetation exhibited increased homogeneity, with denser shrub and herb layers, likely resulting from diminished tree canopy, particularly in hornbeam and ash forests. Homogenization was manifested by the colonization of plants with conservative life-history strategies (higher leaf dry matter content) to cope with increased drought. Consequently, communities with fewer species increased their species richness, while species-rich communities experienced impoverishment. Conversely, herbaceous species with higher specific leaf area were declining. Compositional changes were particularly prominent in hornbeam and oakwoods at the drier end of moisture gradient where the understorey became dominated by woody plants. Ashwoods were opening up due to ash dieback by fungal pathogens, causing replacement of wetland forbs by nitrophilous forbs and woody saplings. The overall number of species decreased in oakwoods but increased in hornbeam and ashwoods due to increased cover of grasses and shade-tolerant woody species, mostly Acer campestre. Conversely, willow understorey vegetation at the wetter end of the moisture gradient remained relatively stable. Our findings suggest shifts towards more homogeneous vegetation. Conservation plans for managing the remnants of species-rich lowland forests should consider the accelerated environmental changes linked to canopy alterations, biological invasions, and extreme climate events.

Why are plant communities stable? Disentangling the role of dominance, asynchrony and averaging effect following realistic species loss scenario

Abstract A growing number of studies have demonstrated that biodiversity is a strong and positive predictor of ecosystem temporal stability by simultaneously affecting multiple underlying mechanisms of stability, that is dominance, asynchrony and averaging effects. However, to date, no study has disentangled the relative role of these key mechanisms of stability in biodiversity experiments. We created a species richness gradient by mimicking a loss of rare species and assessed the role of species richness on community stability and, more importantly, quantified the relative role of three stabilizing mechanisms, that is dominance (stabilization due to stable dominants compared to the rest of the species in the community), asynchrony (stabilization due to temporal asynchrony between species), and averaging effects (pure effect of diversity) on community stability across a species richness gradient. We found that extreme species loss negatively impacted community stability, but just three species were enough to stabilize biomass production to a level similar to highly diverse communities. However, the similar stability of communities resulted from differing contributions from each stabilizing mechanism, depending on the community diversity. Since less abundant species were more temporally variable, species loss stabilized the populations of the remaining species. The loss of rare and subordinate species reduced the dominance and averaging effects, but increased the asynchrony effect. Hence, the asynchrony effect played a major role in the stability of species poor communities, while the averaging effect drove most of the stability of species rich communities. Overall, dominance played only a minor role, accounting for 5%–15% of the stabilization, while asynchrony and averaging effects were dominating forces contributing to ~85%–95% of the total stabilization. Synthesis. This study highlights the importance of biodiversity and roles of dominant and rare species for long‐term community stability and, for the first time, disentangles relative roles of dominance effect, asynchrony and averaging effect on community stability in a real‐world biodiversity experiment.

Multigenerational Drought Reveals a Stable Wheat Seed Fungal Community

Wheat ( Triticum spp.) is a staple food crop, providing a fifth of the world's protein and caloric needs. Our research examines the impact of multigeneration postflowering drought stress on the wheat seed endophytic fungal community. Understanding how wheat seed fungal communities respond to drought stress over several generations can improve our knowledge of legacy drought stress. In this article, we aim to identify seed-associated fungi that play critical roles within the wheat seed under drought stress conditions. We examined the endophytic seed fungal communities of three winter wheat cultivars, Catawba, Shirley, and USG 3640. Moderate drought was imposed on a subset of plants immediately after flowering, with plants relieved from drought stress after 1 week. Seeds harvested from generation 1 were planted for a second generation of drought experiments. When examining the postflowering drought impact on wheat physiology, drought-exposed plants consistently exhibited lower daily transpiration rates, chlorophyll-a values, and seed yield compared with control plants, indicating that drought implementation was successful. Internal transcribed spacer 1 metabarcoding revealed that wheat seed fungal community species richness decreased during postanthesis drought stress across both generations. We also observed that generation accounted for variation in fungal species richness and community structure, independent of drought treatment. The most abundant taxa recovered across all cultivars, treatments, and generations included Cladosporium, Penicillium, Alternaria, and Epicoccum. These results support our hypothesis that postanthesis drought shapes the wheat seed fungal community.

Revisiting the invasion paradox: Resistance-richness relationship is driven by augmentation and displacement trends.

Host-associated resident microbiota can protect their host from pathogens-a community-level trait called colonization resistance. The effect of the diversity of the resident community in previous studies has shown contradictory results, with higher diversity either strengthening or weakening colonization resistance. To control the confounding factors that may lead to such contradictions, we use mathematical simulations with a focus on species interactions and their impact on colonization resistance. We use a mediator-explicit model that accounts for metabolite-mediated interactions to perform in silico invasion experiments. We show that the relationship between colonization resistance and species richness of the resident community is not monotonic because it depends on two underlying trends as the richness of the resident community increases: a decrease in instances of augmentation (invader species added, without driving out resident species) and an increase in instances of displacement (invader species added, driving out some of the resident species). These trends hold consistently under different parameters, regardless of the number of compounds that mediate interactions between species or the proportion of the facilitative versus inhibitory interactions among species. Our results show a positive correlation between resistance and diversity in low-richness communities and a negative correlation in high-richness communities, offering an explanation for the seemingly contradictory trend in the resistance-diversity relationship in previous reports.

Stand diversity increases pine resistance and resilience to compound disturbance

BackgroundDrought, fire, and insects are increasing mortality of pine species throughout the northern temperate zone as climate change progresses. Tree survival may be enhanced by forest diversity, with growth rates often higher in mixed stands, but whether tree defenses are likewise aided remains in question. We tested how forest diversity-productivity patterns relate to growth and defense over three centuries of climate change, competition, wildfire, and bark beetle attack. We used detailed census data from a fully mapped 25.6-ha forest dynamics plot in California, USA to conduct a spatially explicit, dendroecological assessment of large-diameter Pinus lambertiana survival following fire reintroduction. Our structural equation models investigated direct and indirect pathways by which growth, defense, and forest composition together mediated pine resistance and resilience.ResultsIn the historical era of frequent, mixed-severity fire (pre-1900), trees that were ultimately resistant or susceptible to the post-fire bark beetle epidemic all showed similar growth and defenses, as measured by axial resin duct traits. During the era of fire exclusion (1901–2012), however, susceptible trees had slower growth. Following fire re-entry in 2013, both growth and defense declined precipitously for susceptible trees, resulting in fatal bark beetle attack. Spatial analysis showed that monodominant crowding by shade-tolerant competitors contributed to the long-term stress that prevented susceptible trees from recuperating defenses quickly following fire re-entry. For beetle-resistant trees, however, we found positive feedbacks between diversity, growth, and survival: trees in species-rich communities had higher growth rates pre-fire, which promoted a rapid recuperation of defenses following fire that helped trees resist bark beetle attack. Overall, this associational resistance outweighed associational susceptibility (+8.6% vs. −6.4% change in individual tree survival odds), suggesting a relaxation effect that ultimately allowed 58% of large pines to survive.ConclusionsThough climate change threatens forest biodiversity, biodiversity is key to forest climate adaptation in return. Our findings demonstrate centennial-scale feedbacks by which forest diversity increases pine resistance and resilience to climate-amplified disturbances. The spatially explicit, dendroecological framework provides new insights into diversity-productivity theory, while also informing climate-adaptive forest management by identifying thresholds of tree density and richness that maximize large pine survival.

Potential distribution and ecological impacts of Acmella radicans (Jacquin) R.K. Jansen (a new Yunnan invasive species record) in China

Background Acmella radicans(Jacquin) R.K. Jansen is a new invasive species record for Yunnan Province, China. Native to Central America, it has also been recently recorded invading other parts of Asia. To prevent this weed from becoming a serious issue, an assessment of its ecological impacts and potential distribution is needed. We predicted the potential distribution of A. radicans in China using the MaxEnt model and its ecological impacts on local plant communities and soil nutrients were explored.ResultsSimulated training using model parameters produced an area under curve value of 0.974, providing a high degree of confidence in model predictions. Environmental variables with the greatest predictive power were precipitation of wettest month, isothermality, topsoil TEB (total exchangeable bases), and precipitation seasonality, with a cumulative contribution of more than 72.70% and a cumulative permutation importance of more than 69.20%. The predicted potential suitable area of A. radicans in China is concentrated in the southern region. Projected areas of A. radicans ranked as high and moderately suitable comprised 5425 and 26,338 km2, accounting for 0.06 and 0.27% of the Chinese mainland area, respectively. Over the 5 years of monitoring, the population density of A. radicans increased while at the same time the population density and importance values of most other plant species declined markedly. Community species richness, diversity, and evenness values significantly declined. Soil organic matter, total N, total P, available N, and available P concentrations decreased significantly with increasing plant cover of A. radicans, whereas pH, total K and available K increased.ConclusionOur study was the first to show that A. radicans is predicted to expand its range in China and may profoundly affect plant communities, species diversity, and the soil environment. Early warning and monitoring of A. radicans must be pursued with greater vigilance in southern China to prevent its further spread.