Low Functional Redundancy Research Articles

Low functional redundancy revealed high vulnerability of the subtropical evergreen broadleaved forests to environmental change

Anthropogenic-induced environmental changes threaten forest ecosystems by reducing their biodiversity and adaptive capacity. Understanding the sensitivity of ecosystem function to loss of diversity is vital in designing conservation strategies and maintaining the resilience of forest ecosystems in a changing world. Here, based on unique combinations of ten functional traits (termed as functional entities; FEs), we quantified the metrics of functional redundancy (FR) and functional vulnerability (FV) in 250 forest plots across five locations in subtropical evergreen broadleaved forests. We then examined the potential impacts of species loss on functional diversity in subtropical forest communities along environmental gradients (climate and soil). Results showed that the subtropical forests displayed a low level of functional redundancy (FR < 2). Over 75 % of the FEs in these subtropical forest communities were composed of only one species, with rare species emerging as pivotal contributors to these vulnerable FEs. The number of FEs and functional redundancy both increased with the rise in species richness, but functional vulnerability decreased with increasing species richness. Climatic factors, especially mean diurnal range, played crucial roles in determining the functions that the forest ecosystem delivers. Under variable temperature conditions, species in each plot were packed into a few FEs, leading to higher functional redundancy and lower functional vulnerability. These results highlighted that rare species contribute significantly to ecosystem functions and the highly diverse subtropical forest communities could show more insurance effects against species loss under stressful environmental conditions.

Freshwater genome-reduced bacteria exhibit pervasive episodes of adaptive stasis

The emergence of bacterial species is rooted in their inherent potential for continuous evolution and adaptation to an ever-changing ecological landscape. The adaptive capacity of most species frequently resides within the repertoire of genes encoding the secreted proteome (SP), as it serves as a primary interface used to regulate survival/reproduction strategies. Here, by applying evolutionary genomics approaches to metagenomics data, we show that abundant freshwater bacteria exhibit biphasic adaptation states linked to the eco-evolutionary processes governing their genome sizes. While species with average to large genomes adhere to the dominant paradigm of evolution through niche adaptation by reducing the evolutionary pressure on their SPs (via the augmentation of functionally redundant genes that buffer mutational fitness loss) and increasing the phylogenetic distance of recombination events, most of the genome-reduced species exhibit a nonconforming state. In contrast, their SPs reflect a combination of low functional redundancy and high selection pressure, resulting in significantly higher levels of conservation and invariance. Our findings indicate that although niche adaptation is the principal mechanism driving speciation, freshwater genome-reduced bacteria often experience extended periods of adaptive stasis. Understanding the adaptive state of microbial species will lead to a better comprehension of their spatiotemporal dynamics, biogeography, and resilience to global change.

Resistance not resilience traits structure macroinvertebrate communities in newly drying stream sections

Transitioning from perennial to non-perennial flow regimes causes ecological shifts in aquatic communities. Aquatic macroinvertebrates deploy resistance and resilience strategies to cope with flow intermittency, crucial in rivers with long-term seasonal dry episodes. Less is known, about how these strategies support community persistence in streams that only recently have experienced drying, and where local assemblages lack such adaptations. Our study conducted two four-season campaigns, separated by a one-year break, to assess macroinvertebrate responses in newly drying intermittent streams by comparing intermittent and perennial stream sections. We characterize communities from structural and functional perspectives, and then evaluate the response at the trait state level. We observed a decline in taxa richness and abundance, but not structural diversity, in response to flow intermittency. Resistance traits are more important than resilient traits in structuring macroinvertebrate communities in newly intermittent stream sections. Taxa in intermittent sections exhibit a smaller trait space, indicating lower functional redundancy. The macroinvertebrate response to intermittency lacks a predictable pattern, suggesting time-dependent and trait-state-specific colonization by adapted taxa and community assembly with resistance and resilience strategies. As river drought increases due to climate change, recognizing the temporal dimension becomes crucial for understanding ecological responses to intermittency.

Restoration promotes ecological functioning through greater complementarity

Restoration projects are increasingly widespread and many promote habitat succession and the diversity and abundance of faunal communities. These positive effects on biodiversity and abundance may extend to enhancing the ecological functioning and resilience of previously degraded ecosystems, but this is rarely quantified. This study surveyed a 200‐ha restoring coastal wetland and three control wetlands in the Maroochy River, eastern Australia to compare the effects of wetland restoration on the consumption of carrion and the biodiversity, abundance, and functional diversity of functionally important fish and crustaceans. Carrion consumption by fish and crustaceans was measured every 6 months from spring 2017 until spring 2021 for nine events using a combination of baited cameras and scavenging assays. We found restoration improved rates of carrion consumption and the biodiversity, functional diversity, and abundance of scavenger species. Despite positive effects on the diversity of scavengers and carrion consumption, the abundance of two species, longfin eels (Anguilla reinhardtii) and mud crabs (Scylla serrata), was the most important predictors of carrion consumption rates. The spatial distribution of carrion consumption was concentrated in areas with high saltmarsh extent, moderate to high mangrove extent, and high salinity, which also resembled the distribution of both longfin eels and mud crabs. We show that restoration can promote the rates of key ecological functions but that increases to functions are likely to be characterized by low functional redundancy and greater complementarity. Therefore, maintaining or increasing the abundance of functionally important species should become a key objective in future restoration projects.

Taxonomic and functional diversity of subtidal benthic communities associated with hard substrates at Crozet archipelago (sub-Antarctic, Southern Ocean)

Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.

The Restructuring of Ecological Networks by the Pleistocene Extinction

Most terrestrial large mammals went extinct on different continents at the end of the Pleistocene, between 50,000 and 10,000 years ago. Besides the loss in species diversity and the truncation of body mass distributions, those extinctions were even more impactful to interaction diversity. Along with each extinction, dozens of ecological interactions were lost, reorganizing species interaction networks, which attained species-poor configurations with low functional redundancy. Extinctions of most large herbivores impacted energy flow and the rates of nutrient cycling, reconfiguring ecosystem-level networks. Because large mammals have high mobility, their loss also shortened seed-dispersal distance and reduced nutrient diffusivity, disrupting spatial networks. This review examines the recent advances in understanding how different types of ecological networks have been restructured by megafaunal extinctions and how this reorganization affected ecosystem functions. ▪Megafaunal extinctions resulted in the loss of multiple ecological interactions in terrestrial systems.▪Interaction loss reshaped different types of ecological networks including food webs and spatial networks.▪The reorganization of ecological networks changed how terrestrial ecosystems are structured and function.

High-resolution optical remote sensing geomorphological mapping of coral reef: Supporting conservation and management of marine protected áreas

Brazilian corals are unique ecosystems with high endemism and low functional redundancy. Hence, mapping its geomorphology is an important step to inferring analyzes on benthic habitats. We observe several difficulties during this mapping of coastal areas by remote sensing and a lack of fine-scale depth data for reef areas in Brazil. The present study aims to present the bathymetry extracted by satellite imagery in murky waters using a mosaic of Sentinel-2 images in Google Earth Engine (GEE) calibrated with field samples. We used the satellite extracted DBM to map the bottom geomorphology through BTM (Benthic Terrain Modeler). We then present the first detailed geomorphological map for the largest marine coastal protected area in Brazil- MPA Costa dos Corais. The geomorphological raster was differentiated into seven classes: Flat Plains, Depressions, Gentle Slopes, Slopes, Terrestrial Reef Flat, Reef Flat, and Crest. Altogether, we estimate >275 km2 of area representing reef structures (coral reef or beachrocks), or about 48% of the total MPA area. Mapping coral reefs can contribute to conservation, particularly in selecting areas for in situ monitoring activities and in prioritizing the application of remedial actions in the event of environmental disasters or threats to coral health, such as oil spills and bleaching episodes. Our findings encourage the applicability of these methodologies in other reef areas and collaborate for the management and monitoring of marine protected areas. In addition, all mapping is available online for any user.

Low redundancy among caddisflies sharing a mid‐mountain stream

AbstractIn fast‐flowing streams, caddisfly larvae are responsible for processes that collectively determine the efficiency with which the detritivore community is able to decompose autochthonous and allochthonous detritus. This ecosystem function ensures high water quality and represents a precious service for resident rural communities. The analysis of δ13C and δ15N in eight caddisfly taxa from a mid‐mountain stream evidenced a remarkable complementarity in their feeding preferences. An aquatic moth mimicking the caddis mode of life was also included in the survey and its feeding niche appeared to be in between the one of caddis taxa. Moderate niche overlap was interpreted in terms of low functional redundancy, implying that in case of a reduction in diversity, no taxon could be a perfect substitute for another, with a loss of functional efficiency. Low redundancy could be caused by niche segregation due to avoidance of competition/interference between taxa. The broad range of δ13C and δ15N described in this study warns against attributing single δ13C and δ15N to Trichoptera as a group, or even to single families. These results contribute to the still poorly known distribution of East African caddisflies and to the characterisation of feeding preferences of Afrotropical trichopteran larvae.

The Coral Triangle and Strait of Malacca are two distinct hotspots of mangrove biodiversity

Knowledge of the biogeography of marine taxa has lagged significantly behind terrestrial ecosystems. A hotspot of marine biodiversity associated with coral reefs is known in the Coral Triangle of the Indo-West Pacific, but until now there was little data with which to evaluate broad patterns of species richness in the coastal fauna of ecosystems other than coral reefs. This data is critically needed for fauna with low functional redundancy like that of mangroves, that are vulnerable to habitat loss and rising sea levels. Here we show that the diversity of mangrove fauna is characterized by two distinct hotspots in the Indo-West Pacific, associated with two habitat types: fringe mangroves in the Coral Triangle, and riverine mangroves in the Strait of Malacca, between the west coast of Peninsular Malaysia and Sumatra. This finding, based on a family of slugs of which the systematics has been completely revised, illustrates an unexpected biogeographic pattern that emerged only after this taxon was studied intensively. Most organisms that live in the mangrove forests of Southeast Asia remain poorly known both taxonomically and ecologically, and the hotspot of diversity of onchidiid slugs in the riverine mangroves of the Strait of Malacca indicates that further biodiversity studies are needed to support effective conservation of mangrove biodiversity.

Saltwater Intrusion Impacts Microbial Diversity and Function in Groundwater Ecosystems

Background: Groundwater ecosystem services provided by microbial communities are essential for the maintenance of water quality. For example, nitrate contamination is a recognised health and ecosystem issue in most groundwater systems, often alleviated through microbial processes. The effects of climate change, including increasing salinity from rising sea levels, or over-abstraction, on these communities are largely unknown. Methods: This study uses a combination of culture-dependent (growth curves, isolation of bacteria) and culture-independent (16S rRNA gene sequencing) methods to identify the potential effects of saltwater intrusion on groundwater microbes and their ecosystem functions. Results: Some groundwater microbial communities are negatively impacted by increasing chloride concentrations, including declines in bacteria responsible for nitrate and ammonia removal. These ecosystems should be prioritised for future protection from sea level rise or increased extraction of groundwater for agriculture and other uses. Other microbial communities are stimulated in the presence of chloride, often caused by an increase in abundance of salt-tolerant heterotrophic bacteria using sugars, peptides, or organic acids for energy. Conclusion: There have been no previous studies investigating the impact of chloride on Aotearoa New Zealand groundwaters. The identification of keystone species that are affected by increasing salinity, which have a disproportionately large effect on the ecosystem and low functional redundancy, is essential. Water management decisions about future abstraction limits and defences against sea level rise can be underpinned by robust scientific knowledge about microbial community sensitivity to salinity.

Heavy metal effects on multitrophic level microbial communities and insights for ecological restoration of an abandoned electroplating factory site

The response of soil microbes to heavy metal pollution provides a metric to evaluate the soil health and ecological risks associated with heavy metal contamination. However, a multitrophic level perspective of how soil microbial communities and their functions respond to long-term exposure of multiple heavy metals remains unclear. Herein, we examined variations in soil microbial (including protists and bacteria) diversity, functional guilds and interactions along a pronounced metal pollution gradient in a field surrounding an abandoned electroplating factory. Given the stressful soil environment resulting from extremely high heavy metal concentrations and low nutrients, beta diversity of protist increased, but that of bacteria decreased, at high versus low pollution sites. Additionally, the bacteria community showed low functional diversity and redundancy at the highly polluted sites. We further identified indicative genus and “generalists” in response to heavy metal pollution. Predatory protists in Cercozoa were the most sensitive protist taxa with respect to heavy metal pollution, whereas photosynthetic protists showed a tolerance for metal pollution and nutrient deficiency. The complexity of ecological networks increased, but the communication among the modules disappeared with increasing metal pollution levels. Subnetworks of tolerant bacteria displaying functional versatility (Blastococcus, Agromyces and Opitutus) and photosynthetic protists (microalgae) became more complex with increasing metal pollution levels, indicating their potential for use in bioremediation and restoration of abandoned industrial sites contaminated by heavy metals.

Estimating Effects of Sea Level Rise on Benthic Biodiversity and Ecosystem Functioning in a Large Meso-Tidal Coastal Lagoon.

Estuaries are among the world's most productive ecosystems, but due to their geographic location, they are at the forefront of anthropogenic pressures. Sea level rise (SLR) is one major consequence of climate change that poses a threat to estuaries with extensive intertidal habitats. The ecological implications of intertidal habitat loss have been largely overlooked despite their likely significance. We aimed to address this knowledge gap by investigating how benthic macroinvertebrate communities and their contributions to ecosystem function are likely to respond to SLR. Based on a spatially extensive dataset (119 sites) from a large coastal lagoon, depth, sediment chlorophyll concentrations, mud content, and average current speed were identified as the main drivers of community compositional turnover. Shifts in benthic community structure and associated functional implications were then evaluated using depth as a proxy for SLR. Three main macrofaunal groups representing intertidal, shallow subtidal, and deep subtidal habitats were identified. Functional trait analysis indicated low functional redundancy for a key intertidal suspension-feeding bivalve (Austrovenus stutchburyi) and the lack of a shallow subtidal functional replacement should intertidal habitats become inundated. These findings strongly suggest SLR and the associated environmental changes will alter estuarine macroinvertebrate communities, with implications for future ecosystem function and resilience.

Bacterial functional redundancy and carbon metabolism potentials in soil, sediment, and water of thermokarst landscapes across the Qinghai-Tibet Plateau: Implications for the fate of permafrost carbon

Permafrost thaw create widespread thermokarst landscapes. As a result, distinct habitats are provided to harbor different bacterial communities in degraded permafrost soil (PBCs), thermokarst lake sediment (SBCs), and lake water (WBCs), driving carbon metabolism differentially. In this study, we investigated functional diversity and redundancy, and carbon metabolism potentials of PBCs, SBCs, and WBCs in thermokarst landscapes across the Qinghai-Tibet Plateau. The results showed that PBCs and SBCs had higher taxonomic and functional alpha diversity than WBCs, while WBCs had lower functional redundancy. WBCs had the highest beta diversity followed by SBCs and PBCs, suggesting strong determination of taxonomic variations on functional differences. Community assembly processes also had significant influences on beta diversity, especially for SBCs. Metabolism pathways of carbohydrate metabolism, methane metabolism, and carbon fixation were enriched differentially in PBCs, SBCs, and WBCs, suggesting different C fate in distinct habitats. Carbohydrate metabolism data suggested that PBCs might have stronger potentials to mineralize a greater diversity of organic carbon substrate than SBCs and WBCs, promoting degradation of organic carbon stocks in degraded permafrost soils. Methane metabolism data showed that SBCs had a stronger methanogenesis potential followed by PBCs and WBCs, while PBCs had a stronger methane oxidation potential. High abundance of genes involving in formaldehyde assimilation might suggested that a large proportion of produced methane might be assimilated by methanotrophs in the thermokarst landscapes. Both aerobic and anaerobic carbon fixation pathways were enriched in PBCs. The results added our understanding of functional properties and biogeochemical carbon cycles in thermokarst landscapes, improving our abilities in accurate modeling of carbon dynamics and the ultimate fate of permafrost carbon in a warming world.

Comparative Morphological, Metabolic and Transcriptome Analyses in elmo1 -/- , elmo2 -/- , and elmo3 -/- Zebrafish Mutants Identified a Functional Non-Redundancy of the Elmo Proteins.

The ELMO protein family consists of the homologues ELMO1, ELMO2 and ELMO3. Several studies have shown that the individual ELMO proteins are involved in a variety of cellular and developmental processes. However, it has poorly been understood whether the Elmo proteins show similar functions and act redundantly. To address this question, elmo1 −/− , elmo2 −/− and elmo3 −/− zebrafish were generated and a comprehensive comparison of the phenotypic changes in organ morphology, transcriptome and metabolome was performed in these mutants. The results showed decreased fasting and increased postprandial blood glucose levels in adult elmo1 −/− , as well as a decreased vascular formation in the adult retina in elmo1 −/− , but an increased vascular formation in the adult elmo3 −/− retina. The phenotypical comparison provided few similarities, as increased Bowman space areas in adult elmo1 −/− and elmo2 −/− kidneys, an increased hyaloid vessel diameter in elmo1 −/− and elmo3 −/− and a transcriptional downregulation of the vascular development in elmo1 −/− , elmo2 −/− , and elmo3 −/− zebrafish larvae. Besides this, elmo1 −/− , elmo2 −/− , and elmo3 −/− zebrafish exhibited several distinct changes in the vascular and glomerular structure and in the metabolome and the transcriptome. Especially, elmo3 −/− zebrafish showed extensive differences in the larval transcriptome and an impaired survivability. Together, the data demonstrated that the three zebrafish Elmo proteins regulate not only similar but also divergent biological processes and mechanisms and show a low functional redundancy.

Spatial turnover of core and occasional bacterial taxa in the plastisphere from a plateau river, China

Plastic surfaces in the environment are a comparatively new niche for microbial colonization, also known as the “plastisphere”. However, our understanding of the core and occasional bacterial taxa in the plastisphere is limited. Here, environmental plastic, water, and sediment samples were collected from 10 sites in a plateau river (Lhasa River, China) in September of 2019. The composition and spatial turnover of core and occasional bacterial taxa in the plastisphere were revealed via 16S rRNA gene sequencing and compared with water and sediment. The results indicated that deterministic processes dominated the habitat specialization that shaped the formation of core and occasional taxa in the plastisphere, water, and sediment of the Lhasa River because the decline in zeta diversity in the plastisphere, water, and sediment was more fitted to a power-law form rather than an exponential form. Proteobacteria (65.9%), Bacteroidetes (16.0%), and Cyanobacteria (11.7%) dominated the plastic core taxa. Core taxa rather than occasional taxa in the plastisphere had a lower (21.7%) proportion of OTUs and a higher (81.7%) proportion of average relative abundance than water and sediment, which were dominant in plastic bacterial communities. The spatial turnover of core and occasional bacterial taxa in the plastisphere was governed by abiotic as well as biotic factors. Specifically, the spatial turnover of core taxa in the plastisphere with high connectivity but low functional redundancy was easily affected by geographical distance, altitude, and heavy metals. Furthermore, strong drug resistance was found in the spatially persistent core taxa in the plastisphere. This study provides empirical support for the spatial turnover (species variation) and potential ecological mechanisms of bacterial communities in the plastisphere from river ecosystems.

Unprecedented Coral Mortality on Southwestern Atlantic Coral Reefs Following Major Thermal Stress

Thermal stress is now considered the major recent cause of coral reef degradation; yet few studies have been conducted describing those effects on Southwestern Atlantic (SWA) reefs. The SWA represents a coral endemism hotspot with low-functional redundancy and therefore high extinction risk. Recent research has suggested a “thermal refuge” potential for SWA; however, evidence could suggest a different trend. We report herein an unprecedented coral mortality on the largest coastal Brazilian Marine Protected Area (MPA) following the worst thermal stress event since 1985. Degree Heating Week (DHW) values over 4.0 were observed for 107 days, averaging 8.70 for the period, with a maximum of 12.1. Average live coral cover was reduced by 18.1% while average turf algae cover increase by 19.3%. Mortality was highest for three coral species, with a mean mortality of 50.8% per transect for Millepora braziliensis, 32.6% for Mussismilia harttii and 16.6% for Millepora alcicornis. Our unique data for SWA indicates that the populations of two Brazilian endemic species (Millepora braziliensis and Mussismilia harttii) are under severe threat from global warming and that overall coral cover has been dramatically reduced. Hence, the idea of a possible “thermal” refugia within the SWA must be taken with caution for this coral endemism hotspot.

New index of functional specificity to predict the redundancy of ecosystem functions in microbial communities.

An ecosystem function is suggested to be more sensitive to biodiversity loss (i.e. low functional redundancy) when focusing on specific-type functions than broad-type functions. Thus far, specific-type functions have been loosely defined as functions performed by a small number of species (facilitative species) or functions involved in utilizing complex substrates. However, quantitative examination of functional specificity remains underexplored. We quantified the functional redundancy of 33 ecosystem functions in a freshwater system from 76 prokaryotic community samples over 3 years. For each function, we used a sparse regression model to estimate the number of facilitative Amplicon Sequence Variants (ASVs) and to define taxon-based functional specificity. We also used Bertz structural complexity to determine substrate-based functional specificity. We found that functional redundancy increased with the taxon-based functional specificity, defined as the proportion of facilitative ASVs (= facilitative ASV richness/facilitative ASV richness + repressive ASV (ASVs reducing functioning) richness). When using substrate-based functional specificity, functional redundancy was influenced by Bertz complexity per se and by substrate acquisition mechanisms. Therefore, taxon-based functional specificity is a better predictive index for evaluating functional redundancy than substrate-based functional specificity. These findings provide a framework to quantitatively predict the consequences of diversity losses on ecosystem functioning.

Drivers of ecological assembly in the hindgut of Atlantic Cod fed a macroalgal supplemented diet

It is difficult to disentangle the many variables (e.g. internal or external cues and random events) that shape the microbiota in the gastrointestinal tract of any living species. Ecological assembly processes applied to microbial communities can elucidate these drivers. In our study, farmed Atlantic cod (Gadus morhua) were fed a diet of 10% macroalgae supplement (Ulva rigida [ULVA] or Ascophyllum nodosum [ASCO] or a non-supplemented control diet [CTRL]) over 12 weeks. We determined the influence of ecological assembly processes using a suite of null-modelling tools. We observed dissimilarity in the abundance of common OTUs over time, which was driven by deterministic assembly. The CTRL samples showed selection as a critical assembly process. While dispersal limitation was a driver of the gut microbiome for fish fed the macroalgae supplemented diet at Week 12 (i.e., ASCO and ULVA). Fish from the ASCO grouping diverged into ASCO_N (normal) and ASCO_LG (lower growth), where ASCO_LG individuals found the diet unpalatable. The recruitment of new taxa overtime was altered in the ASCO_LG fish, with the gut microbiome showing phylogenetic underdispersion (nepotistic species recruitment). Finally, the gut microbiome (CTRL and ULVA) showed increasing robustness to taxonomic disturbance over time and lower functional redundancy. This study advances our understanding of the ecological assembly and succession in the hindgut of juvenile Atlantic cod across dietary treatments. Understanding the processes driving ecological assembly in the gut microbiome, in fish research specifically, could allow us to manipulate the microbiome for improved health or resilience to disease for improved aquaculture welfare and production.

Lower functional redundancy in “narrow” than “broad” functions in global soil metagenomics

Abstract. Understanding the relationship between soil microbial taxonomic compositions and functional profiles is essential for predicting ecosystem functions under various environmental disturbances. However, even though microbial communities are sensitive to disturbance, ecosystem functions remain relatively stable, as soil microbes are likely to be functionally redundant. Microbial functional redundancy may be more associated with “broad” functions carried out by a wide range of microbes than with “narrow” functions in which specific microorganisms specialize. Thus, a comprehensive study to evaluate how microbial taxonomic compositions correlate with broad and narrow functional profiles is necessary. Here, we evaluated soil metagenomes worldwide to assess whether functional and taxonomic diversities differ significantly between the five broad and the five narrow functions that we chose. Our results revealed that, compared with the five broad functions, soil microbes capable of performing the five narrow functions were more taxonomically diverse, and thus their functional diversity was more dependent on taxonomic diversity, implying lower levels of functional redundancy in narrow functions. Co-occurrence networks indicated that microorganisms conducting broad functions were positively related, but microbes specializing in narrow functions were interacting mostly negatively. Our study provides strong evidence to support our hypothesis that functional redundancy is significantly different between broad and narrow functions in soil microbes, as the association of functional diversity with taxonomy was greater in the five narrow than in the five broad functions.

Temporal effects of fine sediment deposition on benthic macroinvertebrate community structure, function and biodiversity likely reflects landscape setting

Globally, excessive fine sediment (particles <2 mm) deposition is acknowledged to have deleterious effects on aquatic biodiversity. However, the impacts are often equivocal possibly reflecting landscape context, although this is rarely considered. To address this, we examined the temporal response of macroinvertebrate taxonomic and functional diversity to experimental fine sediment clogging in a prealpine (Italy) and lowland setting (UK). Colonisation devices were installed insitu with either clean or clogged substrates and examined for short (7–14 days), medium (21–28 days) and long (56–63 days) timescales. Clogging resulted in altered taxonomic community composition in both the lowland and prealpine rivers and modified functional community composition in the prealpine river. Nestedness was consistently found to be the dominant process driving differences in taxonomic composition between the clean and clogged substrates in the prealpine environment, with clogged substrates forming a nested community. No dominant component structured lowland taxonomic communities. Functional community composition was driven by nestedness in both environments but was heavily dominant in the case of the prealpine river, possibly reflecting low functional redundancy. Widely employed community richness metrics (EPT, taxa and functional richness) only displayed a response to fine sediment loading in the prealpine environment but taxa characterized as sensitive to fine sediment as well as some functional feeding groups did exhibit differences in both settings. In the prealpine environment, the effects of fine sediment intensified over time for several community metrics. Although further research is required to corroborate our findings and extend our observations across more rivers and typologies, excessive fine sediment is a pervasive stressor affecting macroinvertebrate communities in prealpine and lowland environments. However, the biodiversity facets that responded to clogging differed between the two landscape settings probably reflecting wider environmental filtering. Monitoring and managing fine sediment loading likely requires context specific approaches to maximise ecological benefits.