Partial Mantel Tests Research Articles

Diversity of Picea omorika (Pančić) Purk. Populations Based on Morpho-anatomical Needle Traits and Bioclimatic Parameters

Picea omorika (Pančić) Purkyne is a well-known endemic conifer species. However, there have been few morpho-anatomical studies to date. Several years ago, preliminary population studies of P. omorika were published, but with the inclusion of additional populations, it became necessary to confirm whether the southernmost population from Mileševka Canyon, also known as var. vukomanii, (Pavlović and Matović 1994), remains distinct from the others. Two-year-old needles from the lower third of the crown were collected in late autumn from seven natural populations of P. omorika from Serbia and from the border with Bosnia and Herzegovina. The variability of ten morpho-anatomical traits and the cross-sectional anatomy of Serbian spruce needles were examined in seven natural populations in Serbia. Needle length was measured with a digital calliper, and the nine other needle traits, needle width, needle thickness, vascular bundle diameter, resin ducts diameter, number of resin ducts, distance between vascular bundle and resin duct, cuticle and epidermal thickness, hypodermal thickness, and hypodermal width, were examined under a light microscope. For most of the traits studied, the Štula population had the highest values, whereas the Bilo population had the lowest. Needles with triangular sections are most common in the southern part of Mt. Tara, while elliptical and rhomboidal sections are characteristic in populations at the edge of the distribution range in Serbia. Multivariate analyses separated populations into two main groups. Both principal component analysis and discriminant analysis indicated population overlap, while cluster analysis identified three main groups. Multivariate analysis of bioclimatic data and a correlation study of morpho-anatomical traits were also performed. Based on bioclimatic parameters, individuals in the populations from Mileševka and Štula showed the most distinct characteristics. Mantel and partial Mantel tests confirmed no correlation between the complete set of morphological traits and bioclimatic parameters, even after adjusting for regional differences.

Landscape Heterogeneity Drives Genetic Diversity in the Highly Dispersive Moss Funaria hygrometrica Hedw.

Funaria hygrometrica, a cosmopolitan moss species known for its remarkable dispersal capacity, was selected as the focal organism to investigate the relationship between landscape features and genetic diversity. Our study encompassed samples collected from two distinct regions: the Spanish Sierra Nevada Mountains (SN), characterized by a diverse landscape with an altitudinal difference of nearly 3500 m within a short distance, and the Murcia Region (MU) in Southeast Spain, characterized by a uniform landscape akin to the lowlands of Sierra Nevada. Genotyping analysis targeted three genetic regions: the nuclear ribosomal internal transcribed spacer (nrITS), the chloroplast rps3-rpl16 region, and the mitochondrial rpl5-rpl16 spacer. Through this analysis, we aimed to assess genetic variability and population structure across these environmentally contrasting regions. The Sierra Nevada populations exhibited significantly higher haplotype diversity (Hd = 0.78 in the highlands and 0.67 overall) and nucleotide diversity (π% = 0.51 for ITS1) compared to the Murcia populations (Hd = 0.35, π% = 0.14). Further investigation unveiled that samples from the lowlands of Sierra Nevada showed a closer genetic affinity to Murcia than to the highlands of Sierra Nevada. Furthermore, the genetic differentiation between highland and lowland populations was significant (ΦST = 0.55), with partial Mantel tests and ResistanceGA analysis revealing a strong correlation between ITS1-based genetic diversity and landscape features, including altitude and bioclimatic variables. Our study elucidated potential explanations for the observed genetic structuring within F. hygrometrica samples' populations. These included factors such as a high selfing rate within restricted habitats, a limited average dispersal distance of spores, hybrid depression affecting partially incompatible genetic lineages, and recent migration facilitated via human activities into formerly unoccupied areas of the dry zones of Southeast Spain.

Different Adaption Strategies of Abundant and Rare Microbial Communities in Sediment and Water of East Dongting Lake.

The dynamics of aquatic microbes is of great importance for comprehending the acclimatisation and evolution of microorganisms in lake ecology. However, little is known about the adaption strategies of microbial communities in East Dongting Lake, which had special and complexity geographical characteristics. A semi-enclosed lake area (A) and a waterway connected to Yangtze River (B) both existed in the lake zone. Here, we investigated bacterial and fungal community diversity, community network and community assembly processes in sediment and water. The results indicated that the proportion of OTU numbers and their relative abundance for rare and abundant taxa were different obviously between sediment and water, but not between bacteria and fungi. However, abundant subcommunities dominated the shifts of bacterial community diversity and structure in A region, while rare subcommunities for fungal community diversity. Compared to fungal community, bacterial network was more compact and more key stones were identified as rare taxa. In addition, stochastic processes (dispersal limitation) drove the community assembly of abundant and rare subcommunities, but the effects of deterministic processes (including variable and heterogeneous selections) affected more on rare rather than abundant taxa. Partial Mantel test further indicated that the effect of environmental factors was a stronger force in shaping abundant bacterial subcommunities (TOC, NH4+-N, TN, and ORP) and rare fungal subcommunities (ORP). Environmental factors explained more of the variation in bacterial community structure than that in fungal community structure, although they had additional effects on fungal community diversity and community assembly. Moreover, bacterial community affected the fungal community as a biotic factor in water. This research provided new insights into better understanding of microbial communities in the complex environment of the East Dongting Lake.

A Global Comparison of Stream Diatom Beta Diversity on Islands Versus Continents Across Scales

ABSTRACTAimTo evaluate the patterns of stream diatom beta diversity in islands versus continents across scales, to relate community similarities with spatial and environmental distances and to investigate the role of island characteristics in shaping insular diatom beta diversity.LocationAfrica, America, Europe and the Pacific.Time PeriodPresent.Major Taxa StudiedStream diatoms.MethodsWe compared diatom beta diversity between islands and continents at large scales (within biogeographic regions) in two study regions (America and Europe) and at small scales (within islands/equivalent areas in continents) in three regions (Africa, America and Europe) partitioning beta diversity into turnover and nestedness components. We used a partial Mantel test and distance–decay curves to assess how diatom beta diversity on islands and continents is affected by spatial and environmental distances. Finally, using island data from all four regions, we evaluated the relationship between island beta diversity and island latitude, area, age and isolation using linear models.ResultsAt large scales, mean dissimilarities were higher on islands than in continents in Europe but lower in America. At smaller scales, the differences varied mostly depending on island isolation. Beta diversity was mainly caused by species turnover. Partial Mantel test and distance–decay curves revealed that spatial and environmental distances shaped diatom beta diversity at large, but not at small scales. Moreover, diatom beta diversity on islands was affected by island latitude, age and isolation, but not by island area.Main ConclusionsDiatom beta diversity on islands versus continents and its responses to spatial and environmental factors are scale and region dependent. Incomplete colonisation, evolutionary processes and environmental filtering likely contribute to insular beta diversity, which further varies with island latitude, age and isolation. This study sheds new light on beta diversity of microorganisms on islands and suggests that beta diversity should be explicitly considered in island biogeographical research.

Revealing synergistic mechanisms of biochar-assisted microbial electrolysis cells in enhancing the anaerobic digestion performance of waste activated sludge: Extracellular polymeric substances characterization, enzyme activity assay, and multi-omics analysis

Although biochar (BC)-assisted microbial electrolysis cells (MEC) has been shown to improve anaerobic digestion (AD) performance of waste activated sludge (WAS), the underlying mechanisms remain unclear. This study conducted an in-depth investigation into the mechanism based on analyses of extracellular polymeric substances (EPS) characteristics, enzyme activities and multi-omics. The results showed that compared with the control group, methane production improved by 16.73 %, 21.32 %, and 29.37 % in the BC, MEC, and BC-assisted MEC (BC-MEC) groups, respectively. The reconfiguration of the protein secondary structure increased the hydrophobicity of the EPS, thereby promoting microbial aggregation. In addition, partial least-squares path modeling (PLS-PM) and mantel test based on the enzyme activity and multi-omics analyses revealed that the promotional effect of MEC on the hydrolysis of WAS was superior to that of BC, while BC was more advantageous in promoting electron transfer and biofilm formation regulated by quorum sensing. The synergistic effects of BC and MEC were exemplified in the BC-MEC group. g_norank_Aminicenantales responsible for the hydrolysis of WAS was enriched (29.6 %), and the activities of hydrolytic enzymes including α-glucosidases and proteases were increased by 29.1 % and 43.6 %, respectively. Further, the expressions of genes related to acyl homoserine lactones (AHLs) and diffusible signal factor (DSF) in quorum sensing systems, as well as the genes related to hydrogenase involved in electron transfer (mbhJKL, hyfB-JR, hypA-F, and hoxFHUY), were up-regulated in the BC-MEC group. This facilitated electron transfer and microbial communication, consequently enhancing methane production. This research significantly advances the understanding of the mechanism by which BC-assisted MEC enhances AD performance and provides valuable insights into strategies for improving energy recovery from WAS.

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.

The joint effects of local, climatic, and spatial variables determine soil oribatid mite community assembly along a temperate forest elevational gradient.

Numerous factors influence mountain biodiversity variation across elevational gradients and recognizing the relative importance is vital for understanding species distribution mechanisms. We examined oribatid mites at nine elevations (from 600 to 2200 m a.s.l) and four vegetation types from mixed coniferous and broad-leaved forests to alpine tundra on Changbai Mountain. We assessed the contribution of environmental factors (climatic and local factors) and spatial processes (geographic or elevation distances) to oribatid mite community assembly and identified 59 oribatid mite species from 38 families and 51 genera. With increasing elevation, species richness and the Shannon index declined significantly, whereas abundance followed a hump-shaped trend. Soil TP, NH4 +-N, MAT, MAP, and elevation were the critical variables shaping oribatid mite communities based on random forest analysis. Moreover, environmental and spatial factors, and oribatid mite communities were significantly correlated based on Mantel and partial Mantel tests. Local characteristics (3.9%), climatic factors (1.9%), and spatial filtering (8.8%) played crucial roles in determining oribatid mite communities across nine elevational bands (based on variation partitioning analyses of abundance data). Within the same vegetation types, spatial processes had relatively little effects, with local characteristics the dominant drivers of oribatid mite community variation. Environmental and spatial filters together shape oribatid mite community assembly and their relative roles varied with elevation and vegetation type. These findings are crucial for the conservation, restoration, and management of Changbai mountain ecosystems in the context of climate change, along with the prediction of future vertical biotic gradient pattern evolution.

Environment and management jointly shape the spatial patterns of plant species diversity of moist grasslands in the mountains of Northeastern Yunnan

Grasslands account for about a quarter of the Earth’s land area and are one of the major terrestrial ecosystems, with significant ecological and economic value. The influence of environmental factors and management types on grassland biodiversity has garnered considerable attention. This study investigated how patterns of species richness are influenced by geographical distance, environmental gradients, and management type in the grasslands of northeastern Yunnan, China. We used structural equation modeling to disentangle the impacts of environment and management on phylogenetic community structure, and partial Mantel tests to estimate the roles of dispersal limitation and environmental filtering on taxonomic and phylogenetic beta diversity of three types of grasslands. Our results show that taxonomic alpha diversity increased in grazed grasslands and decreased in mowed grasslands, compared with protected grasslands. However, the phylogenetic structure of both grazed and mowed grassland communities was clustered, whereas that of protected communities was random. Moreover, both grazing and mowing significantly reduced the taxonomic and phylogenetic beta diversity of grasslands, with the lowest values observed in mowed grasslands. Both taxonomic and phylogenetic beta diversity were dominated by species turnover under different management types. The taxonomic and phylogenetic beta diversities of protected and grazed grasslands were simultaneously affected by environmental filtering and dispersal limitation, with the later playing a stronger role. In addition, mowing and related management measures had a stronger filtering effect on grassland community structure, as reflected by changes in community composition.

Long-Term Analysis of Regional Vegetation Correlation with Climate and Phenology in the Midsection of Maowusu Sandland

It is essential to monitor the dynamics of vegetation at different scales in space and time to promote the sustainable development of terrestrial ecosystems. We used the Google Earth Engine (GEE) cloud platform to perform a comprehensive analysis of the changes in normalized difference vegetation index (NDVI) Mann-Kendall (MK) + Sen trend in the hinterland region of the Maowusu sandland in China over the last two decades. We performed bias-correlation studies using soil and climate data. Furthermore, we performed a partial Mantel test to analyze the spatial and temporal fluctuations of vegetation health-related indices. Additionally, we developed a logistic dual model of the phenology index using the Lenvenberg–Marquardt technique. The objective was to uncover the factors contributing to the regional shifts in vegetation dynamics. We provide a comprehensive analytic method designed to monitor vegetation over some time and forecast its future recovery. The findings indicate that over the past 20 years, more than 90% of the regional NDVI in the study area has exhibited a consistent and significant upward trend. This trend is primarily influenced by the adverse impact of temperature and the beneficial impact of precipitation. Additionally, long-term phenological indicators in the study area reveal that the vegetation’s growth cycle commences on the 125th day of the year and concludes on the 267th day of the year. This suggests that the shorter duration of the vegetation’s growth season may be attributed to the local climate and unfavorable groundwater depth conditions. levated temperatures throughout the next spring and autumn seasons would significantly affect the wellbeing of plants, with soil moisture being a crucial determinant of plant development in the examined region. This study presents a wide range of analytical tools for monitoring vegetation over a long period and predicting its future recovery. It considers factors such as vegetation health, phenology, and climatic influences. The study establishes a solid scientific foundation for understanding the reasons behind regional vegetation changes in the future.

Regional β-Diversity of Stream Insects in Coastal Alabama Is Correlated with Stream Conditions, Not Distance among Sites.

β-diversity is often measured over both spatial and temporal gradients of elevation, latitude, and environmental conditions. It is of particular interest to ecologists, as it provides opportunities to test and infer potential causal mechanisms determining local species assemblages. However, studies of invertebrate β-diversity, especially aquatic insects, have lagged far behind other biota. Using partial Mantel tests, we explored the associations between β-diversity of insects found in the coastal streams of Alabama, USA, and stream conditions and distances among sites. β-diversity was expressed using the Sørensen index, βSor, stream conditions were expressed as principal components (PCs), and distances as Euclidean distances (km) among sites. We also investigated the impact of seasonality (fall, summer) and taxonomic resolution (genus, species) on βSor. Regardless of season, βSor was significantly correlated (p < 0.01; r > 0.44) with stream conditions (stream size and water chemistry), while taxonomic resolution had minimal effect on associations between βSor and stream conditions. Distance was never correlated with changes in βSor (p > 0.05). We extended the use of the Sørensen pair-wise index to a multiple-site dissimilarity, βMult, which was partitioned into patterns of spatial turnover (βTurn) and nestedness (βNest). Changes in βMult were driven mostly by turnover rather than nestedness.

Long‐term processes between Classic and Postclassic populations in the Mexico basin

AbstractThe study of nonmetric traits is useful for establishing biological differences or affinities between populations. This study considered 12 nonmetric cranial characters. The objective is to compare five series of two different cultural horizons: three populations of the Teotihuacán Classic period and two of the Mexica Postclassic period. For the selection of nonmetric traits, those not altered by intentional cephalic modification were considered. From the sample of materials, it was assessed whether the populations of the Classic period could have biological and cultural affinity between them, making a migratory interpretation which indicates differences in nonmetric characters between them. The mean measure of divergence (MMD) was considered as bio‐distance. The distance matrix was analyzed using the unweighted pair group method with arithmetic mean and nonmetric multidimensional scaling. Frequencies were studied using the principal component analysis. Mantel test and partial Mantel test were used to compare the distance matrix obtained with the MMD with sites geographical distance matrix, type of settlements matrix, and period of the site's matrix. In none of those cases were found a correlation at the level. Making more plausible that the results of the nonmetric traits MMD matrix agree with a migration process. All methods agree on separating Classical populations into one group and Postclassic populations into another. The archeological contexts, and the study of the material culture found, agree with the analysis of nonmetric characters.

Environmental and spatial factors play different roles in phytoplankton community assembly in different hydrological seasons in Lake Wuchang, China

Lake phytoplankton communities are affected by environmental and spatial factors. We studied the relative importance of environmental and spatial factors on the phytoplankton community assembly in Lake Wuchang across three hydrological seasons, which were divided into dry (December to March), normal (April to June, October to November) and wet seasons (July to September) based on the water level and depth. Spatial and temporal patterns of environmental factors and phytoplankton community composition and diversity were studied using Kruskal–Wallis test, Wilcoxon test and NMDS. CCA, Mantel and partial Mantel tests, and PLS-PM were used to investigate the effects of environmental and spatial factors on phytoplankton community characteristics. Results showed that phytoplankton assemblages at the eight study sites were composed of totally 244 species belonging to 9 phyla, which changed from Bacillariophyta and Chlorophyta to Cyanophyta across the whole hydrological period. There was significantly higher abundance and biomass in the normal and wet seasons than that in the dry season. Phytoplankton alpha diversity exhibited uniform temporal distribution patterns with higher values in the dry season than in the normal and wet seasons. The Mantel and partial Mantel tests revealed that environmental (physicochemical conditions of lake water) and spatial factors (geographic distances among sites) jointly affected the phytoplankton community structure and beta diversity across the hydrological seasons, while spatial factors were more important in the wet season. Partial least squares path models showed that spatial factors exhibited a significant positive correlation with the phytoplankton diversity with the path coefficients of 0.53 and 0.71 in the normal and wet seasons, respectively. Phytoplankton composition had significant correlation with on phytoplankton diversity with the path coefficient of −0.75 and 0.61 in the normal and wet seasons, respectively. Our findings revealed that both environmental and spatial factors affected the phytoplankton community assembly in Lake Wuchang. Environmental factors played a more important role in the dry season, while spatial factors were more important in the wet season. With the exception of the abiotic factors (environmental and spatial), the impacts of biotic factors on phytoplankton community cannot be ignored. Therefore, it is also necessary to strengthen further research on the top-down control over phytoplankton communities in Lake Wuchang.

Unveiling the impact and mechanisms of Cd-driven ecological assembly and coexistence of bacterial communities in coastal sediments of Yellow Sea

The microbial community assembly processes and underlying mechanisms in response to heavy metal accumulation in coastal sediments remain underexplored. In this study, the heavy metal concentration in samples were found below the marine sediment quality standards. Through partial Mantel tests and linear regression analysis, Cd was identified as the major influencing factor, displaying strongest correlation with the bacterial community in the sediments. The class Desulfuromonadia was identified as a biomarker which showed enrichment in the sediments with high Cd content. Additionally, the results of null model and the neutral community model demonstrated the prominent role of stochastic processes in the assembly of bacterial community. However, with the increase in Cd concentration, the influence of selection processes intensified, resulting in a decline in species migration rate and subsequent reduction in ecological niche width. Furthermore, the intensified competition and an increase in keystone species among bacterial populations further enhanced the stability of the microbial co-occurrence network in response to high Cd concentration. This study offers an insight into the effects of heavy metal on microbial assembly and coexistence, which are conducive to marine ecosystem management and conservation.

Anthropogenic original DOM is a critical factor affecting LNA bacterial community assembly

We investigated the geographical and environmental distance–decay relationships for both of the two bacteria in the Haihe River, Tianjin, China. HNA bacteria exhibited a stronger geographical variation-dependent pattern while LNA bacteria exhibited a stronger environmental variation-dependent pattern. Variance partition analysis (VPA), Mantel test, and partial mantel test validated the discrepant impacts of geographical distance and environmental factors on their two communities. The heterogeneous selection dominated community assembly of LNA bacteria demonstrates their greater sensitivity to environmental conditions. As the deterministic environmental factor, anthropogenic original dissolved organic matter (DOM) functions exclusively on LNA bacteria, and it is the critical factor leading to the discrepant biogeographical patterns of LNA and HNA bacteria. LNA bacteria interact with HNA bacteria and mediate the DOM driving total bacteria assembly. The LNA keystone taxa, Pseudomonas, Rheinheimera, Candidatus Aquiluna, and hgcl clade are capable to compete with HNA bacteria for anthropogenic original DOM, and are potential indicators of anthropogenic pollution. Our research reveals the non-negligible effect of the LNA bacteria in regulating the ecological response of total bacteria.

Genetic diversity of a flightless dung beetle appears unaffected by wildfire

The wildfires of Australia’s Black Summer in 2019/2020 caused a massive loss of wildlife and habitats, but the effects of the fire on invertebrate species post-burn are unknown. We hypothesised that the fires would negatively affect the genetic diversity of invertebrate species by impeding movement between populations due to habitat loss. We studied the genetic diversity of a flightless dung beetle, Amphistomus primonactus Matthews 1974, to determine the impact of the wildfires on this species. We examined 90 SNPs from 193 individuals across seven localities impacted by the wildfires in north-eastern New South Wales. We used STRUCTURE to determine the overall population structure of the seven localities. We calculated four within-locality genetic diversity measures (observed heterozygosity (Ho), unbiased expected heterozygosity (uHe), Shannon’s Information (1H), and the inbreeding coefficient (FIS). We calculated three between-locality genetic diversity measures (Fixation Index (FST), Hedrick’s G”ST, and Shannon’s Mutual Information (I). We used partial Mantel tests to compare the between-locality genetic diversity measures with the mean fire intensity along each pairwise linear transect, while accounting for genetic variation due to geographic distance. We compared the within-locality genetic diversity measures to the mean fire intensity at each site. STRUCTURE showed a large degree of intermixing between localities. We found no significant effect of fire on any within-locality genetic diversity measure, or on any between-locality genetic diversity measure. We suggest that the genetic diversity of A. primonactus was not significantly affected by the Black Summer wildfires.Implications for insect conservation: Our results show that the 2019/2020 wildfires had a negligible impact on the genetic structure of A. primonactus. This offers a promising outlook for the species in its recovery from the fires.

Biotic and Abiotic Factors Controlling Spatial Variation of Mean Carbon Turnover Time in Forest Soil

AbstractSoil carbon persistence in forests plays a pivotal role in regulating terrestrial feedback to climate change. However, the relative contributions of biotic and abiotic factors in controlling geographic variation of forest soil carbon turnover time (τsoc) remains unclear. Here, we first sampled soils from 12 permanent forest plots across eastern China and detected higher radiocarbon‐derived mean turnover time of soil organic carbon in the deep (30–100 cm; 2,087 ± 246 years) than the surface (0–30 cm; 249 ± 80 years) layer. Further analyses based on the partial Mantel test and structural equation model illustrated that the interactions of climate, vegetation, and soil factors are more complex in deep than surface soils. Then, we established a global database of radiocarbon‐derived τsoc from 1897 forest soil samples. On the global scale, τsoc was significantly higher in the deep (3,081 ± 398 years) than the surface (332 ± 56 years) layer. Soil depth alone explained 11.7% of the spatial variation in τsoc, and the interactions between climate, stand age, and soil depth account for 68.6% of the variation. These findings highlight the joint control of climate, vegetation, and soil depth in the spatial variation of soil carbon persistence in global forests.

Insights on the assembly processes and drivers of soil microbial communities in different depth layers in an abandoned polymetallic mining district

Soil microbes, which play crucial roles in maintaining soil functions and restoring degraded lands, are impacted by heavy metal pollution. This study investigated the vertical distribution of bacterial communities along the soil profiles across four types of areas (heavy metal pollution level: tailings heap area > phytoremediation area > natural restoration area > original forest area) in an abandoned polymetallic mining district by 16S rRNA sequencing, and aimed to disentangle the assembly mechanisms and key drivers of the vertical variation in bacterial community structure. Bacterial diversity and composition were found to vary remarkably between the depth layers in all types of areas, with heterogeneous selection dominated the vertical distribution pattern of soil bacterial communities. Pearson correlation analysis and partial Mantel test revealed that soil nutrients mainly shaped the vertical distribution of bacterial microbiota along soil profiles in the original forest and natural restoration areas. Ni, As, and bioavailable As were the key drivers regulating the vertical variation of bacterial assemblages in the phytoremediation area, whereas Pb, pH, soil organic carbon, and available nitrogen were crucial drivers in the tailings heap area. These findings reveal the predominant assembly mechanisms and drivers governing the vertical distribution of soil bacterial microbiota and indicate the efficiency of phytoremediation and ecological restoration on ameliorating edaphic micro-ecosystems in heavy metal-contaminated areas.

Driving factors of soil bacterial biogeographical distribution in three alpine grassland types

AbstractThe biogeographic distribution of plants and animals on the Qinghai–Tibetan Plateau (QTP) has been extensively studied; however, the biogeographic patterns and factors affecting bacterial communities in alpine grassland ecosystems over large scales were not fully understood. In this paper, we explored the biogeographic patterns of soil bacterial communities in wet meadow, meadow, and steppe. The results showed that bacterial α‐diversity was similar in the three grassland types, while bacterial β‐diversity differed significantly. The dominant bacteria were Proteobacteria (29.86%), Acidobacteriota (17.76%), and Actinobacteriota (16.42%), which were caused by the changes in soil pH, C/N, and soil moisture. In addition, the significant distance–decay of bacterial communities was found across environmental and geographical distances. Partial Mantel test showed that the differences of bacterial community in wet meadow and meadow were influenced by environmental and geographical factors, while the difference of bacterial community in steppe was only affected by geographical distance. The MRM accounted for 38.7%, 37.2%, and 11.8% of the variability in wet meadow, meadow, and steppe, respectively. In wet meadow and meadow, geographic distance was the most powerful factor in explaining the similarity of bacterial communities, while soil moisture was the most critical factor in steppe. It was obvious that environmental and geographical factors played different roles in shaping structures of bacterial community in wet meadow, meadow, and steppe, which provided new insights for the effective management of alpine grassland.

Genomic insights into genetic diversity and local adaptation of a dominant desert steppe feather grass, Stipa breviflora Griseb.

Investigating the genetic mechanisms of local adaptation is critical to understanding how species adapt to heterogeneous environments. In the present study, we analyzed restriction site-associated DNA sequencing (RADseq) data in order to explore genetic diversity, genetic structure, genetic differentiation, and local adaptation of Stipa breviflora. In total, 135 individual plants were sequenced and 25,786 polymorphic loci were obtained. We found low genetic diversity (He=0.1284) within populations of S. breviflora. Four genetic clusters were identified along its distribution range. The Mantel test, partial Mantel test, and multiple matrix regression with randomization (MMRR) indicate that population differentiation was caused by both geographic distance and environmental factors. Through the FST outlier test and environmental association analysis (EAA), 113 candidate loci were identified as putatively adaptive loci. RPK2 and CPRF1, which are associated with meristem maintenance and light responsiveness, respectively, were annotated. To explore the effects of climatic factors on genetic differentiation and local adaptation of S. breviflora, gradient forest (GF) analysis was applied to 25,786 single nucleotide polymorphisms (SNPs) and 113 candidate loci, respectively. The results showed that both temperature and precipitation affected the genetic differentiation of S. breviflora, and precipitation was strongly related to local adaptation. Our study provides a theoretical basis for understanding the local adaptation of S. breviflora.

Focusing on the role of abiotic and biotic drivers on cross-taxon congruence

Diversity patterns can show congruence across taxonomic groups. Consistent diversity patterns allow the identification of indicator surrogates potentially representative of unobserved taxa or the broader biodiversity patterns. However, the effective use of biodiversity surrogates depends on underlying mechanisms driving the strength of the relationship among taxonomic groups. Here, we explored congruence patterns in community composition among taxa occupying different trophic levels, accounting for abiotic and biotic factors: vascular plants and six groups of ground-dwelling arthropods (pseudoscorpions, spiders, darkling beetles, rove beetles, ground beetles and ants) were chosen as potential indicator surrogates. We evaluated the cross-taxon relationships using Mantel test; subsequently, we investigated if these relationships could partially depend on abiotic drivers, using partial Mantel tests; then, we evaluated the partial contributions of abiotic and biotic drivers in explaining these relationships through a series of variation partitioning analyses. Our results showed that a consistent cross-taxon congruence pattern was evident across almost all group pairs: pseudoscorpions, spiders, ground beetles and vascular plants showed the largest number of significant correlations with other taxa. Environmental gradients resulted as drivers of cross-taxon congruence, shaping composition patterns. However, they were not the only ones. Biotic drivers account for part of cross-taxon congruence among vascular plants and arthropod predators (i.e., pseudoscorpions and spiders, but also ground beetles), as well as among taxa at high trophic levels. Almost all strictly predatory taxa, known as biological control agents, emerged as the best predictors of plant community composition even when the role of environmental factors was considered. Spiders/ants and spiders/ground beetles showed close relationships and congruent composition patterns, irrespective of environmental parameters. Relationships among taxa might be driven by several complex biotic interactions (e.g., non-trophic and trophic interactions, direct and indirect interactions). Bottom-up and top-down forces, consumptive and non-consumptive interactions may play a role in influencing the community composition of taxa and driving the observed relationships. Future studies should broaden knowledge about the role of these forces and interactions in determining the congruence across taxa. The multi-trophic perspective in cross-taxon studies can be promising for identifying biodiversity surrogates and their application in conservation planning.