Patterns Of Community Composition Research Articles

Glimpsing the 2020 spring bloom in the Strait of Georgia (Canada) with autonomous ferry-based sensors

Spatiotemporal observations are data rich and offer insights into links between ecological patterns and underlying processes. We present fine-scale autonomous observations from repeated ferry transects in the Strait of Georgia (British Columbia, Canada) during the 2020 spring bloom period using a FerryBox system (temperature, salinity, chlorophyll a fluorescence) and a digital inline holographic microscope. Despite instrument cleaning interruptions related to COVID-19 restrictions, 3 periods from late winter (February) to springtime (March and April) contained 14 days of high-quality holograms (>70000) capturing >10500 identifiable micro- to mesoplankton using automatic object detection. The ferry set-up provided automatic data storage through Ocean Networks Canada, which also automatized data flagging and guaranteed remote access. The highest-quality holograms repeatedly covered the central and eastern Strait and showed aspects of bloom succession. Fast-growing diatoms (Skeletonema sp.) emerged first, followed by a diverse assemblage including Chaetoceros spp., Ditylum spp., and Eucampia spp., and by April, larger centric cells prevailed. The combined approach captured local suppression of chlorophyll a fluorescence and diatom concentrations in Fraser River plume waters during the freshet, suggesting fine-scale spatial patterns in seasonal planktonic community composition. This work is among the first of its kind to autonomously generate in situ imaging and physicochemical data with spatiotemporal resolution.

Effect of Altitude Gradients on the Spatial Distribution Mechanism of Soil Bacteria in Temperate Deciduous Broad-Leaved Forests

Soil bacteria are an important part of the forest ecosystem, and they play a crucial role in driving energy flow and material circulation. Currently, many uncertainties remain about how the composition and distribution patterns of bacterial communities change along altitude gradients, especially in forest ecosystems with strong altitude gradients in climate, vegetation, and soil properties. Based on dynamic site monitoring of the Baiyun Mountain Forest National Park (33°38′–33°42′ N, 111°47′–111°51′ E), this study used Illumina technology to sequence 120 soil samples at the site and explored the spatial distribution mechanisms and ecological processes of soil bacteria under different altitude gradients. Our results showed that the composition of soil bacterial communities varied significantly between different altitude gradients, affecting soil bacterial community building by influencing the balance between deterministic and stochastic processes; in addition, bacterial communities exhibited broader ecological niche widths and a greater degree of stochasticity under low-altitude conditions, implying that, at lower altitudes, community assembly is predominantly influenced by stochastic processes. Light was the dominant environmental factor that influenced variation in the entire bacterial community as well as other taxa across different altitude gradients. Moreover, changes in the altitude gradient could cause significant differences in the diversity and community composition of bacterial taxa. Our study revealed significant differences in bacterial community composition in the soil under different altitude gradients. The bacterial communities at low elevation gradients were mainly controlled by stochasticity processes, and bacterial community assembly was strongly influenced by deterministic processes at middle altitudes. Furthermore, light was an important environmental factor that affects differences. This study revealed that the change of altitude gradient had an important effect on the development of the soil bacterial community and provided a theoretical basis for the sustainable development and management of soil bacteria.

Water physicochemical quality as driver of spatial and temporal patterns of microbial community composition in lake ecosystems

This study aimed at monitoring and management of the surface water and potentially pathogenic microbes of Lake Tonga (Algeria) with respect to. It characterized the main bacterial diversity patterns of Lake Tonga and predicted from water physicochemical parameters and water quality index (WQI) the distribution of bacterial species and the main indicator groups of faecal water contamination. Water samples were taken monthly at three sampling sites of different water depths. Several physicochemical parameters were measured; of which some were included in computing WQI to characterize the water quality of the lake. Counting, isolation and bacterial identification methods were used to characterize the existing aerobic heterotrophic bacteria. The composition of the microbial community of the waterbody of Lake Tonga included an abundant culturable bacterial flora belonging to several bacterial families and whose specific richness varied between water depths of the sites sampled. Species richness of the bacteria identified phenotypically varied between 7 and 11 per sample. The site with shallow water was the richest in bacterial species, compared to moderate and deep waters. The redundancy analysis showed the main physicochemical drivers of the microbial community composition. Our findings showed that high WQI scores indicated the water quality deterioration which triggered the increase in total load of faecal indicator bacterial groups. This study identified in Lake Tonga an important culturable aerobic bacterial flora whose specific richness and distribution varied spatially following the effects of water physicochemical parameters. Lake Tonga needs an integrated management plan to mitigate human disturbances declining water quality.

The scimitar-cat Homotherium from the submerged continental shelf of the Gulf Coast of Texas.

The machairodontine felid Homotherium achieved a global geographic distribution throughout much of the Pleistocene. Accordingly, that large carnivore is important for understanding patterns of community composition. We report on a new record of Homotherium based on a fragmentary premaxilla-maxilla discovered on McFaddin Beach, Texas, along the Gulf of Mexico. Skeletal remains of extinct, Pleistocene vertebrates accumulate on McFaddin Beach. Those fossils appear to originate from submerged deposits on the continental shelf in the Gulf of Mexico, an area that was subaerially exposed in the Late Pleistocene during glacial intervals. Marine erosion and transport altered the externally visible morphology of the current specimen, obscuring and/or damaging taxonomically informative details of the preserved dentition. However, high-resolution X-ray computed tomography revealed diagnostic portions of the unerupted crown of an upper canine within its alveolus. The serrated edges of the canine combined with the position of the incisors demonstrate that the specimen from McFaddin Beach represents a species of Homotherium. That specimen is the latest in a larger sample of Homotherium in Texas that spans most of the Pliocene-Pleistocene. This is the first occurrence of Homotherium from the continental shelf of the Gulf Coast. That landscape may have formed a broad subtropical Gulf Coast corridor that facilitated the dispersal of Neotropical taxa along the coast between Texas and Florida. The associated fauna from McFaddin Beach contains Neotropical mammals common to southern Texas and Florida and indicates that Homotherium was a member of the fauna inhabiting the Gulf Coast corridor during the Late Pleistocene.

Exploring fish communities in the mud volcano polluted river using environmental DNA metabarcoding

In ecosystems subjected to environmental disturbances such as mud volcanoes, understanding the dynamics of fish communities is essential for ecological assessment and conservation. This study employs environmental DNA (eDNA) metabarcoding for the first time to explore fish communities within a challenging and unique environment—a mud volcano-polluted river. High-throughput sequencing was utilized to assess alpha and beta diversity, revealing distinct patterns in fish community composition in response to mud discharge activity. The results indicate that affected sites exhibit remarkably different communities during active and inactive mud discharge, with the impact extending downstream to the river mouth. Notably, the application of eDNA metabarcoding identified a vulnerable species, Rasbora lateristriata, emphasizing its utility in detecting high-risk species. Despite challenges in species identification and reference databases, the use of longer 16S rRNA fragments offered enhanced taxonomic resolution and interspecific sequence variation. This approach showcases the potential of eDNA metabarcoding in assessing fish diversity and community dynamics in polluted aquatic ecosystems, emphasizing its significance in biodiversity surveys and ecological monitoring. The study underscores the value of eDNA metabarcoding as an efficient and comprehensive tool for studying freshwater ecosystems and highlights the need for expanding reference databases to address genetic coverage gaps, particularly in less-studied environments.

Plant Community Composition and Structural Pattern Dynamics in Robe-Raya Natural Forest, Southeast Ethiopia

Due to its fortuitous mix of geography, terrain, and geology, Ethiopia is the home of unique assemblages of rich biodiversity. However, this impressive biological diversity is increasingly threatened by the combined effects of different drivers before they are sufficiently investigated. The present work was carried out in Robe-Raya Natural Forest, located in Southeast Ethiopia, with the intention of examining plant community formation and structural dynamics of the forest species. Sixty (20 m × 20 m) quadrats were placed at 100 m distance along eleven east-west directed transect lines systematically. In order to gather juvenile’s data, five subquadrats (2 m × 2 m) were established within the main quadrat, distributed at each corner and middle. In each quadrat, all woody species were recorded and counted; diameter (DBH) and height were measured using tape meter and a hypsometer, respectively, and cover abundance was recorded (in %). Cluster analysis was computed using R-Package to map-out the community types. Species diversity and composition among community types were computed using the Shannon-Wiener index and Sorenson’s coefficient, respectively. Frequency, density, height, DBH, basal area, and IVI were used to analyze structural dynamics. Age-class density ratios were used to examine the regeneration status. Ninety-four woody plant species belonging to 39 families were documented. Asteraceae was the most species-rich family (10 species). The common growth form was shrubs (44.7%) followed by trees (41.5%). Cluster analysis produced four community types. In total, the species diversity and evenness were 3.75 and 0.88, respectively. The forest density and basal area were 1183.3 stems/ha and 57.52 m2·ha−1, respectively. Structural dynamics analyses demonstrated that the forest was composed of, largely, young trees and shrubs and under fair regeneration status. Certain species that have been identified to have low IVI and poor regeneration status should be prioritized for conservation.

Interaction between phytoplankton and heterotrophic bacteria in Arctic fjords during the glacial melting season as revealed by eDNA metabarcoding.

The hydrographic variability in the fjords of Svalbard significantly influences water mass properties, causing distinct patterns of microbial diversity and community composition between surface and subsurface layers. However, surveys on the phytoplankton-associated bacterial communities, pivotal to ecosystem functioning in Arctic fjords, are limited. This study investigated the interactions between phytoplankton and heterotrophic bacterial communities in Svalbard fjord waters through comprehensive eDNA metabarcoding with 16S and 18S rRNA genes. The 16S rRNA sequencing results revealed a homogenous community composition including a few dominant heterotrophic bacteria across fjord waters, whereas 18S rRNA results suggested a spatially diverse eukaryotic plankton distribution. The relative abundances of heterotrophic bacteria showed a depth-wise distribution. By contrast, the dominant phytoplankton populations exhibited variable distributions in surface waters. In the network model, the linkage of phytoplankton (Prasinophytae and Dinophyceae) to heterotrophic bacteria, particularly Actinobacteria, suggested the direct or indirect influence of bacterial contributions on the fate of phytoplankton-derived organic matter. Our prediction of the metabolic pathways for bacterial activity related to phytoplankton-derived organic matter suggested competitive advantages and symbiotic relationships between phytoplankton and heterotrophic bacteria. Our findings provide valuable insights into the response of phytoplankton-bacterial interactions to environmental changes in Arctic fjords.

Influences of the Integrated Rice-Crayfish Farming System with Different Stocking Densities on the Paddy Soil Microbiomes.

Integrated rice-fish farming has emerged as a novel agricultural production pattern to address global food security challenges. Aiming to determine the optimal, scientifically sound, and sustainable stocking density of red claw crayfish (Cherax quadricarinatus) in an integrated rice-crayfish farming system, we employed Illumina high-throughput 16S rRNA gene sequencing to evaluate the impact of different stocking densities of red claw crayfish on the composition, diversity, function, and co-occurrence network patterns of soil bacterial communities. The high stocking density of red claw crayfish reduced the diversity and evenness of the soil bacterial community during the mid-culture stage. Proteobacteria, Actinobacteria, and Chloroflexi emerged as the most prevalent phyla throughout the experimental period. Low stocking densities initially boosted the relative abundance of Actinobacteria in the paddy soil, while high densities did so during the middle and final stages. There were 90 distinct functional groups identified across all the paddy soil samples, with chemoheterotrophy and aerobic chemoheterotrophy being the most abundant. Low stocking densities initially favored these functional groups, whereas high densities enhanced their relative abundances in the later stages of cultivation. Medium stocking density of red claw crayfish led to a more complex bacterial community during the mid- and final culture stages. The experimental period showed significant correlations with soil bacterial communities, with total nitrogen (TN) and total phosphorus (TP) concentrations emerging as primary factors contributing to the alterations in soil bacterial communities. In summary, our findings demonstrated that integrated rice-crayfish farming significantly impacted the soil microbiomes and environmental factors at varying stocking densities. Our study contributed to theoretical insights into the profound impact of integrated rice-crayfish farming with various stocking densities on bacterial communities in paddy soils.

Flying by the river side: Survey of bat distributions and environmental contexts along a 1000‐mile river corridor, Green and Colorado Rivers, USA

AbstractAimEmerging research shows how bioindicators, specifically bats, can serve as a means for monitoring conservation and management of riparian corridors for multiple taxonomic groups. To track changes in the composition or abundance of bioindicator species, researchers must attain a baseline in species presence and relative activity. We examined the spatial and temporal patterns of bat community composition and activity along a 1000‐mile river corridor to determine species diversity trends by latitude and habitat.LocationColorado River Basin.MethodsHere we describe the results from an acoustic bat survey conducted opportunistically on the 2019 Sesquicentennial Colorado River Exploring Expedition. This broad, 1000‐mile survey provides a baseline for species distributions over a large geographic range.ResultsIn total, we collected 63 nights of acoustic data over 70 days and recorded over 59,000 files equating to 45,363 caLL files (≥2 pulses). 18,490 (41% of caLL files) were identified as species (n = 19 bat species). We applied non‐metric multidimensional scaling to characterize spatiotemporal patterns of activity between species, as well as compared bat activity among river features and local environmental conditions (i.e., temperature and time since sunset) using an information theoretic approach.ConclusionSpecies composition varied by physiographic region and adjacent river habitat, thus providing a quantifiable measure of determining habitat quality along this major river system and providing baseline information for using bats as bioindicators of habitat quality.

Unveiling the diversity, composition, and dynamics of phyllosphere microbial communities in Alhagi sparsifolia across desert basins and seasons in Xinjiang, China.

Phyllosphere microbes residing on plant leaf surfaces for maintaining plant health have gained increasing recognition. However, in desert ecosystems, knowledge about the variety, composition, and coexistence patterns of microbial communities in the phyllosphere remains limited. This study, conducted across three basins (Turpan-TLF, Tarim-CL, and Dzungaria-MSW) and three seasons (spring, summer, and autumn) in Xinjiang, China, aimed to explore the diversity and composition of microbial communities in the phyllosphere, encompassing both bacteria and fungi in Alhagi sparsifolia. We also investigated the co-occurrence patterns, influencing factors, and underlying mechanisms driving these dynamics. Results indicate that phyllosphere bacteria exhibited lower diversity indices (ACE, Shannon, Simpson, Fisher phylogenetic diversity, and Richness) in spring compared to summer and autumn, while the Goods Coverage Index (GCI) was higher in spring. Conversely, diversity indices and GCI of phyllosphere fungi showed an opposite trend. Interestingly, the lowest level of multi-functionality and niche width in phyllosphere bacteria occurred in spring, while the highest level was observed in phyllosphere fungi. Furthermore, the study revealed that no significant differences in multi-functionality were found among the regions (CL, MSW, and TLF). Network analysis highlighted that during spring, phyllosphere bacteria exhibited the lowest number of nodes, edges, and average degree, while phyllosphere fungi had the highest. Surprisingly, the multi-functionality of both phyllosphere bacteria and fungi showed no significant correlation with climatic and environmental factors but displayed a significant association with the morphological characteristics and physicochemical properties of leaves. Structural Equation Model indicated that the morphological characteristics of leaves significantly influenced the multi-functionality of phyllosphere bacteria and fungi. However, the indirect and total effects of climate on multi-functionality were greater than the effects of physicochemical properties and morphological characteristics of leaves. These findings offer new insights into leaf phyllosphere microbial community structure, laying a theoretical foundation for vegetation restoration and rational plant resource utilization in desert ecosystems.

Microbial difference and its influencing factors in ice-covered lakes on the three poles

Most lakes in the world are permanently or seasonally covered with ice. However, little is known about the distribution of microbes and their influencing factors in ice-covered lakes worldwide. Here we analyzed the microbial community composition in the waters of 14 ice-covered lakes in the Hoh Xil region of northern Qing-Tibetan Plateau (QTP), and conducted a meta-analysis by integrating published microbial community data of ice-covered lakes in the tripolar regions (the Arctic, Antarctica and QTP). The results showed that there were significant differences in microbial diversity, community composition and distribution patterns in the ice-covered tripolar lakes. Microbial diversity and richness were lower in the ice-covered QTP lakes (including the studied lakes in the Hoh Xil region) than those in the Arctic and Antarctica. In the ice-covered lakes of Hoh Xil, prokaryotes are mainly involved in S-metabolic processes, making them more adaptable to extreme environmental conditions. In contrast, prokaryotes in the ice-covered lakes of the Arctic and Antarctica were predominantly involved in carbon/nitrogen metabolic processes. Deterministic (salinity and nutrients) and stochastic processes (dispersal limitation, homogenizing dispersal and drift) jointly determine the geographical distribution patterns of microorganisms in ice-covered lakes, with stochastic processes dominating. These results expand the understanding of microbial diversity, distribution patterns, and metabolic processes in polar ice-covered lakes.

Rehydration under extreme drought conditions affected rhizosphere microorganisms more than bulk soil in broomcorn millet farmland

Rehydration is a primary adaptation strategy for alleviating the detrimental effects of drought on crop growth. However, the effects of rehydration on microbial communities in various compartments under drought conditions remain poorly understood. Herein, we explored the response patterns of bacterial and fungal community composition, diversity, ecological network, and assembly process in the bulk soil and rhizosphere of broomcorn millet farmland at 5, 10, 20, and 30 days after rehydration during drought conditions. Compared to drought, rehydration significantly decreased the organic matter (OM), total nitrogen (TN), available potassium (AK), available phosphorus (AP), nitrate nitrogen (NO3--N), and ammonium nitrogen (NH4+-N) contents in rhizosphere, but had no obvious influences on the OM and TN contents in bulk soil on the four sampling days. In the rhizosphere of broomcorn millet field, Firmicutes and Actinobacteria were enriched in drought condition, but Proteobacteria and Bacteroidetes were enriched in rehydration regime. Compared to drought, the relative abundances of Eurotiomycetes, Dothideomycetes, Mortierellomycetes, and Leotiomycetes were enhanced, but Sordariomycetes was reduced on the 5th and 10th days after rehydration. Rehydration increased the bacterial and fungal observed ASVs and Shannon index in the rhizosphere to varying degrees, but had little effect on the bulk soil. Null-model analysis indicated that rehydration deceased the stochastic process of fungal communities in the bulk soil, whereas had no influence on deterministic process of bacterial community in the bulk soil and rhizosphere. More importantly, rhizosphere properties had a greater impact on the bacterial and fungal community composition, diversity, and assembly process than bulk soil. Network analysis revealed that rehydration improved the interconnected taxa in the rhizosphere bacterial network, but reduced microbial interactions in the rhizosphere fungal network compared to drought. This work provides a theoretical foundation for elucidating the role of rehydration regime in governing the ecological services of microbiome of broomcorn millet farmland under drought conditions.

Seasonality and longer-term development generate temporal dynamics in the Populus microbiome.

Temporal variation in community composition is central to our understanding of the assembly and functioning of microbial communities, yet the controls over temporal dynamics for microbiomes of long-lived plants, such as trees, remain unclear. Temporal variation in tree microbiomes could arise primarily from seasonal (i.e., intra-annual) fluctuations in community composition or from longer-term changes across years as host plants age. To test these alternatives, we experimentally isolated temporal variation in plant microbiome composition using a common garden and clonally propagated plants, and we used amplicon sequencing to characterize bacterial/archaeal and fungal communities in the leaf endosphere, root endosphere, and rhizosphere of two Populus spp. over four seasons across two consecutive years. Microbial community composition differed among seasons and years (which accounted for up to 21% of the variation in microbial community composition) and was correlated with seasonal dissimilarity in climatic conditions. However, microbial community dissimilarity was also positively correlated with time, reflecting longer-term compositional shifts as host trees aged. Together, our findings demonstrate that temporal patterns in tree microbiomes arise from both seasonal fluctuations and longer-term changes, which interact to generate unique seasonal patterns each year. In addition to shedding light on two important controls over the assembly of plant microbiomes, our results also suggest future studies of tree microbiomes should account for background temporal dynamics when testing the drivers of spatial patterns in microbial community composition and temporal responses of plant microbiomes to environmental change.IMPORTANCEMicrobiomes are integral to the health of host plants, but we have a limited understanding of the factors that control how the composition of plant microbiomes changes over time. Especially little is known about the microbiome of long-lived trees, relative to annual and non-woody plants. We tested how tree microbiomes changed between seasons and years in poplar (genus Populus), which are widespread and ecologically important tree species that also serve as important biofuel feedstocks. We found the composition of bacterial, archaeal, and fungal communities differed among seasons, but these seasonal differences depended on year. This dependence was driven by longer-term changes in microbial composition as host trees developed across consecutive years. Our findings suggest that temporal variation in tree microbiomes is driven by both seasonal fluctuations and longer-term (i.e., multiyear) development.

Pathogen community composition and co-infection patterns in a wild community of rodents

Pathogen community composition and co-infection patterns in a wild community of rodents

Climate and Environmental Variables Drive Stream Biofilm Bacterial and Fungal Diversity on Tropical Mountainsides.

High mountain freshwater systems are particularly sensitive to the impacts of global warming and relevant environmental changes. Microorganisms contribute substantially to biogeochemical processes, yet their distribution patterns and driving mechanism in alpine streams remain understudied. Here, we examined the bacterial and fungal community compositions in stream biofilm along the elevational gradient of 745-1874 m on Mt. Kilimanjaro and explored their alpha and beta diversity patterns and the underlying environmental drivers. We found that the species richness and evenness monotonically increased towards higher elevations for bacteria, while were non-significant for fungi. However, both bacterial and fungal communities showed consistent elevational distance-decay relationships, i.e., the dissimilarity of assemblage composition increased with greater elevational differences. Bacterial alpha diversity patterns were mainly affected by chemical variables such as total nitrogen and phosphorus, while fungi were affectedby physical variables such as riparian shading and stream width. Notably, climatic variables such as mean annual temperature strongly affected the elevational succession of bacterial and fungal community compositions. Our study is the first exploration of microbial biodiversity and their underlying driving mechanisms for stream ecosystems in tropical alpine regions. Our findings provide insights on the response patterns of tropical aquatic microbial community composition and diversity under climate change.

Ecological succession of abundant and rare subcommunities during aerobic composting in the presence of residual amoxicillin

Aerobic composting increases the content of soluble nutrients and facilitates the safe treatment of livestock manure. Although different taxa play crucial roles in maintaining ecological functionality, the succession patterns of community composition and assembly of rare and abundant subcommunities during aerobic composting under antibiotic stress and their contributions to ecosystem functionality remain unclear. Therefore, this study used 16 S rRNA gene sequencing technology to reveal the response mechanisms of diverse microbial communities and the assembly processes of abundant and rare taxa to amoxicillin during aerobic composting. The results indicated that rare taxa exhibited distinct advantages in terms of diversity, community composition, and ecological niche width compared with abundant taxa, highlighting their significance in maintaining ecological community dynamics. In addition, deterministic (heterogeneous selection) and stochastic processes (dispersal limitation) play roles in the community succession and functional dynamics of abundant and rare subcommunities. The findings of this study may contribute to a better understanding of the relative importance of deterministic and stochastic assembly processes in composting systems, and the ecological functions of diverse microbial communities, ultimately leading to improved ecological environment.

Diskontinuum Gornje Neretve: gradienti taksonomske in funkcionalne raznolikosti bentoških nevretenčarjev v divji balkanski reki

Free-flowing rivers are highly valuable to understand the taxonomic and functional community structure of organisms that inhabit fluvial ecosystems. We investigated patterns of macroinvertebrate community composition and food web structure using stable isotopes (δ13C and δ15N), including potential environmental drivers, over a free-flowing river continuum in the upper course of the Neretva River in Bosnia and Herzegovina. Results showed a high taxonomic diversity, a high percentage of EPT taxa (Ephemeroptera, Plecoptera, Trichoptera), and a slightly heterotrophic ecosystem (average allochthonous assimilation = 54%). The taxonomic composition differed prominently between a tributary located upstream and the mainstem. However, we also found notable species turnover between the upper (headwater and midsection) reaches and the downstream reaches of the mainstem. Macroinvertebrate abundance and the percentage of EPT peaked downstream while midsection reaches showed the highest taxonomic richness and diversity and allochthonous assimilation. Most of the functional metrics (maximum and average trophic position and isotopic richness and evenness) showed pronounced discontinuities in their spatial patterns, which did not follow the predictions of the River Continuum Concept. These results highlight the uniqueness of this section of the Neretva, where natural discontinuities structure macroinvertebrate communities in ways and by mechanisms not captured by smooth ecological concepts.

Heavy metal contamination impacts the structure and co-occurrence patterns of bacterial communities in agricultural soils.

Heavy metal (HM) contamination caused by mining and smelting activities can be harmful to soil microbiota, which are highly sensitive to HM stress. Here, we explore the effects of HM contamination on the taxonomic composition, predicted function, and co-occurrence patterns of soil bacterial communities in two agricultural fields with contrasting levels of soil HMs (i.e., contaminated and uncontaminated natural areas). Our results indicate that HM contamination does not significantly influence soil bacterial α diversity but changes the bacterial community composition by enriching the phyla Gemmatimonadetes, Planctomycetes, and Parcubacteria and reducing the relative abundance of Actinobacteria. Our results further demonstrate that HM contamination can strengthen the complexity and modularity of the bacterial co-occurrence network but weaken positive interactions between keystone taxa, leading to the gradual disappearance of some taxa that originally played an important role in healthy soil, thereby possibly reducing the resistance of bacterial communities to HM toxicity. The predicted functions of bacterial communities are related to membrane transport, amino acid metabolism, energy metabolism, and carbohydrate metabolism. Among these, functions related to HM detoxification and antioxidation are enriched in uncontaminated soils, while HM contamination enriches functions related to metal resistance. This study demonstrated that microorganisms adapt to the stress of HM pollution by adjusting their composition and enhancing their network complexity and potential ecological functions.

Effect of fire and post-fire management on soil microbial communities in a lower subtropical forest ecosystem after a mountain fire

Wildfires and post-fire management exert profound effects on soil properties and microbial communities in forest ecosystems. Understanding microbial community recovery from fire and what the best post-fire management should be is very important but needs to be sufficiently studied. In light of these gaps in our understanding, this study aimed to assess the short-term effects of wildfire and post-fire management on both bacteria and fungi community composition, diversity, structure, and co-occurrence networks, and to identify the principal determinants of soil processes influencing the restoration of these communities. Specifically, we investigated soil bacterial and fungal community composition, diversity, structure, and co-occurrence networks in lower subtropical forests during a short-term (<3 years) post-fire recovery period at four main sites in Guangdong Province, southern China. Our results revealed significant effects of wildfires on fungal community composition, diversity, and co-occurrence patterns. Network analysis indicated reduced bacterial network complexity and connectivity post-fire, while the same features were enhanced in fungal networks. However, post-fire management effects on microbial communities were negligible. Bacterial diversity correlated positively with soil microbial biomass nitrogen, soil organic carbon, and soil total nitrogen. Conversely, based on the best random forest model, fungal community dynamics were negatively linked to nitrate-nitrogen and soil water content. Spearman's correlation analysis suggested positive associations between bacterial networks and soil factors, whereas fungal networks exhibited predominantly negative associations. This study elucidates the pivotal role of post-fire management in shaping ecological outcomes. Additionally, it accentuates the discernible distinctions between bacterial and fungal responses to fire throughout a short-term recovery period. These findings contribute novel insights that bear significance in evaluating the efficacy of environmental management strategies.

Plumage microorganism communities of tidal marsh sparrows

Microorganism communities can shape host phenotype evolution but are often comprised of thousands of taxa with varied impact on hosts. Identification of taxa influencing host evolution relies on first describing microorganism communities and acquisition routes. Keratinolytic (keratin-degrading) microorganisms are hypothesized to be abundant in saltmarsh sediments and to contribute to plumage evolution in saltmarsh-adapted sparrows. Metabarcoding was used to describe plumage bacterial (16S rRNA) and fungal (ITS) communities in three sparrow species endemic to North America's Atlantic coast saltmarshes. Results describe limited within-species variability and moderate host species-level patterns in microorganism diversity and community composition. A small percentage of overall microorganism diversity was comprised of potentially keratinolytic microorganisms, warranting further functional studies. Distinctions between plumage and saltmarsh sediment bacteria, but not fungal, communities were detected, suggesting multiple bacterial acquisition routes and/or vertebrate host specialization. This research lays groundwork for future testing of causal links between microorganisms and avian host evolution.