Composition Of Biological Communities Research Articles

Microhabitat-specific differences on the composition and function of biological soil crust communities

Microhabitat-specific differences on the composition and function of biological soil crust communities

Cover Cropping Increases Soil Fungal-Bacterial Community Diversity and Network Complexity in Apple Orchards on the Loess Plateau, China

Soil microorganisms play a key role in soil fertility. Exploring the microbial community composition and diversity in response to cover crops is important for improving soil fertility in orchards. This study investigated how cover cropping can improve soil fertility by altering microbial community composition and the interrelations among soil microorganisms. Soil physicochemical and biological indicators and microbial community composition were evaluated after a 6-years application of cover cropping in an apple (Malus pumila cv. Fuji) orchard located on the Loess Plateau, China. Three treatments were applied: Trifolium repens treatment (TR), Lolium perenne treatment (LP), clear tillage treatment (CT). The soil of the cover crop treatments had a more complex microbial co-occurrence network than that of the clear tillage treatment; in particular, the correlations among fungi were significantly increased. Cover cropping increased the levels of soil organic matter (SOM), microbial biomass carbon (MBC), and total nitrogen (TN) in orchard soil. Changes in the fungal community were more related to microbial biomass nitrogen (MBN), TN, and carbon-nitrogen ratio (C:N). This indicates that cover cropping not only increases the diversity of soil microorganisms but also increases the interrelations between microbial groups, thereby improving the soil fertility of apple orchards on the Loess Plateau.

Dung beetles maintain phylogenetic divergence but functional convergence across a highly fragmented tropical landscape

Abstract Understanding how human‐modified landscapes affect the phylogenetic composition and assembly mechanisms of biological communities is critical for effectively managing and restoring tropical ecosystems. We evaluated how forest coverage loss, fragmentation and landscape heterogeneity affect the phylogenetic diversity of dung beetles and their assembly mechanisms in Los Tuxtlas Biosphere Reserve, a protected but highly fragmented tropical landscape. We calculated Faith's phylogenetic diversity, mean pairwise phylogenetic distance and mean nearest taxon distance for 5,388 individuals in 36 species. The standardised effect sizes of these metrics were estimated to control their correlation with species richness. Phylogenetic diversity was also assessed separately for each dung beetle functional group. Finally, we compared the mean functional and phylogenetic pairwise distance and mean nearest taxon distance and measured the phylogenetic signal among dung beetle functional traits to determine the influence of niche conservatism on the phylogenetic structure of species assemblages. Faith's phylogenetic diversity of dung beetles was positively correlated with forest coverage, while their mean phylogenetic and nearest taxon distance values decreased with increasing landscape fragmentation. Necrophagous beetles and forest specialists responded most negatively to forest coverage loss and fragmentation. Alpha and beta diversity values showed phylogenetic overdispersion but functional convergence and weak phylogenetic signals in their functional traits, suggesting low niche conservatism. Landscapes with moderate forest coverage (≥40%) favoured higher phylogenetic beta diversity, whereas phylogenetic and functional beta diversity decreased significantly in landscapes with low forest coverage (<30%). Synthesis and applications. Forest habitats in fragmented landscapes are essential for safeguarding the evolutionary history of dung beetles, reducing biotic homogenisation processes by favouring phylogenetic overdispersion and complementarity between sites. Therefore, to secure the phylogenetic diversity of dung beetles within fragmented tropical reserves, we recommend protecting the existing forests, preventing further fragmentation of continuous forest areas and increasing matrix quality by implementing biodiversity‐friendly production systems. Finally, managers should consider assessing different functional groups in other species, as their response to landscape disturbance may not be phylogenetically similar. The above will allow more effective management practices to protect the species most susceptible to disturbances.

Response of the biological community to the translocation of seaweed attaching substrate

Artificial reefs (ARs) are often used to restore and develop seaweed beds. However, few studies have reported the changes of biological community on the substrate surface before and after the attaching substrates were transferred. In this study, the response of the biological community, including macrobiotic biofouling and microbial community, to translocation of seaweed attaching substrate were investigated. The results showed that the seaweed coverage ratio significantly reduced after the translocation, the macrobiotic biofouling community diversity on attaching substrates increased after the translocation, and the transplanted substrates had more percentage cover and lower biodiversity than the untransplanted substrates. In addition, highest diversity was found on microbial community after the translocation. Non-metric multidimensional scaling (NMDS) revealed that the microbial community on the transfered substrates was significantly different from that before and without transfer. Co-occurrence network analysis showed that the degree of bacterial community network connection was highest before the translocation. The result revealed that the translocation of seaweed substrate could affect the biological community composition, and could accelerate the changes in macrobiotic biofouling community on the back of substrates.

Shifts in DNA yield and biological community composition in stored sediment: implications for paleogenomic studies

Lake sediments hold a wealth of information from past environments that is highly valuable for paleolimnological reconstructions. These studies increasingly apply modern molecular tools targeting sedimentary DNA (sedDNA). However, sediment core sampling can be logistically difficult, making immediate subsampling for sedDNA challenging. Sediment cores are often refrigerated (4 °C) for weeks or months before subsampling. We investigated the impact of storage time on changes in DNA (purified or as cell lysate) concentrations and shifts in biological communities following storage of lake surface sediment at 4 °C for up to 24 weeks. Sediment samples (~ 0.22 g, in triplicate per time point) were spiked with purified DNA (100 or 200 ng) or lysate from a brackish water cyanobacterium that produces the cyanotoxin nodularin or non-spiked. Samples were analysed every 1–4 weeks over a 24-week period. Droplet digital PCR showed no significant decrease in the target gene (nodularin synthetase – subunit F; ndaF) over the 24-week period for samples spiked with purified DNA, while copy number decreased by more than half in cell lysate-spiked samples. There was significant change over time in bacteria and eukaryotic community composition assessed using metabarcoding. Amongst bacteria, the cyanobacterial signal became negligible after 5 weeks while Proteobacteria increased. In the eukaryotic community, Cercozoa became dominant after 6 weeks. These data demonstrate that DNA yields and community composition data shift significantly when sediments are stored chilled for more than 5 weeks. This highlights the need for rapid subsampling and appropriate storage of sediment core samples for paleogenomic studies.

Influence of seascape spatial pattern on the trophic niche of an omnivorous fish

AbstractHabitat fragmentation of submerged aquatic vegetation (SAV) transforms the spatial pattern of seascapes by changing both the total area and spatial configuration of the habitat patches. The ecological effects of SAV seascapes are most often assessed using metrics of biological community composition (e.g., species and assemblage changes). We know considerably less about the effects of seascape structure on ecological processes such as food web function and energy flow. Here, we assess the difference in the trophic niche of Pinfish (Lagodon rhomboides, a generalist omnivore) across a spatial gradient of SAV from continuous to highly fragmented seascapes in Biscayne Bay (Miami, Florida, USA). The Bay seascapes are influenced by freshwater management practices that alter the distribution of SAV habitat and fish species abundance, diversity, and community assemblage. We combined SAV seascape maps with stable isotope and hypervolume analyses to determine how trophic niche size and overlap varied with changes in the seascape. We observed similar resource use across the seascape, but trophic niche size increased in more fragmented SAV seascapes, suggesting diversification of trophic roles and energy flow pathways. Pinfish collected from more continuous SAV habitats had smaller trophic niche size and higher trophic levels. Both trophic response metrics manifested a threshold response that depended on distinct SAV spatial characteristics (amount vs. spatial configuration) and environmental conditions. Our results suggest that habitat fragmentation of SAV seascape structure has ecological implications that could affect energy flow with cascading consequences for food web stability and ecosystem functioning.

Exploring the coupled ocean and atmosphere system with a data science approach applied to observations from the Antarctic Circumnavigation Expedition

Abstract. The Southern Ocean is a critical component of Earth's climate system, but its remoteness makes it challenging to develop a holistic understanding of its processes from the small scale to the large scale. As a result, our knowledge of this vast region remains largely incomplete. The Antarctic Circumnavigation Expedition (ACE, austral summer 2016/2017) surveyed a large number of variables describing the state of the ocean and the atmosphere, the freshwater cycle, atmospheric chemistry, and ocean biogeochemistry and microbiology. This circumpolar cruise included visits to 12 remote islands, the marginal ice zone, and the Antarctic coast. Here, we use 111 of the observed variables to study the latitudinal gradients, seasonality, shorter-term variations, geographic setting of environmental processes, and interactions between them over the duration of 90 d. To reduce the dimensionality and complexity of the dataset and make the relations between variables interpretable we applied an unsupervised machine learning method, the sparse principal component analysis (sPCA), which describes environmental processes through 14 latent variables. To derive a robust statistical perspective on these processes and to estimate the uncertainty in the sPCA decomposition, we have developed a bootstrap approach. Our results provide a proof of concept that sPCA with uncertainty analysis is able to identify temporal patterns from diurnal to seasonal cycles, as well as geographical gradients and “hotspots” of interaction between environmental compartments. While confirming many well known processes, our analysis provides novel insights into the Southern Ocean water cycle (freshwater fluxes), trace gases (interplay between seasonality, sources, and sinks), and microbial communities (nutrient limitation and island mass effects at the largest scale ever reported). More specifically, we identify the important role of the oceanic circulations, frontal zones, and islands in shaping the nutrient availability that controls biological community composition and productivity; the fact that sea ice controls sea water salinity, dampens the wave field, and is associated with increased phytoplankton growth and net community productivity possibly due to iron fertilisation and reduced light limitation; and the clear regional patterns of aerosol characteristics that have emerged, stressing the role of the sea state, atmospheric chemical processing, and source processes near hotspots for the availability of cloud condensation nuclei and hence cloud formation. A set of key variables and their combinations, such as the difference between the air and sea surface temperature, atmospheric pressure, sea surface height, geostrophic currents, upper-ocean layer light intensity, surface wind speed and relative humidity played an important role in our analysis, highlighting the necessity for Earth system models to represent them adequately. In conclusion, our study highlights the use of sPCA to identify key ocean–atmosphere interactions across physical, chemical, and biological processes and their associated spatio-temporal scales. It thereby fills an important gap between simple correlation analyses and complex Earth system models. The sPCA processing code is available as open-access from the following link: https://renkulab.io/gitlab/ACE-ASAID/spca-decomposition (last access: 29 March 2021). As we show here, it can be used for an exploration of environmental data that is less prone to cognitive biases (and confirmation biases in particular) compared to traditional regression analysis that might be affected by the underlying research question.

Niche shifts after island colonization spurred adaptive diversification and speciation in a cosmopolitan bird clade.

Islands have long been recognized as key contributors to biodiversity because they facilitate geographic isolation and ecological divergence from mainland ancestors. However, island colonization has traditionally been considered an evolutionary dead-end process, and its consequences for continental biodiversity remain understudied. Here, we use the evolutionary radiation of Columbiformes (i.e. pigeons and doves) to examine if ecological niche shifts on islands shaped biological diversification and community composition on continents. We show that the colonization of islands by continental, terrestrial-foraging lineages led to the exploitation of a new ecological niche (i.e. arboreal foraging). This transition towards arboreal foraging was associated with evolutionary adaptation towards a new morphological optimum. In addition, arboreal-foraging lineages of islands experienced an increase in speciation rates, which was associated with successful range expansions to other islands as well as back colonization of continents. Our results provide empirical evidence that diversification on continents can only be fully understood when studying the diversification processes that took place on islands, challenging the view of islands as mere sinks of evolutionary diversity.

Impact of human disturbance on temporal partitioning within carnivore communities

Abstract Interspecific competition is an important evolutionary force, influencing interactions between species and shaping the composition of biological communities. In mammalian carnivores, to reduce the risks of negative encounters between competitors, species can employ a strategy of temporal partitioning, adapting activity patterns to limit synchronous activity. This strategy of non‐human competitor avoidance, however, may be influenced by the expansion of human activities, which has driven wild mammals towards nocturnality. We hypothesise that the disruption of temporal niche partitioning by humans and their activities could increase temporal overlap between carnivores, enhancing interspecific competition. We reviewed the published literature systematically and employed generalised linear models to evaluate quantitatively the relative influence of a range of human, meteorological and ecological variables on coefficients of temporal overlap within mammalian terrestrial carnivore communities (orders Carnivora and Didelphimorphia) on a global scale. None of the models investigated showed evidence of an impact of humans on temporal partitioning between carnivores on a global scale. This illustrates that temporal avoidance of humans and competitors does not always follow a consistent pattern and that its strength may be context‐dependent and relative to other dimensions of niche partitioning (spatial and trophic). Similarly, the regulation of activity patterns may be strongly site‐specific and may be influenced by a combination of biotic and abiotic characteristics. Temporal avoidance of both humans and competitors by carnivores may take the form of short, reactive responses that do not impact activity patterns in the longer term. Although we did not detect a global disruption of temporal partitioning due to human disturbance, carnivore communities may still experience an increase in interspecific competition in other niche dimensions. Further research would benefit from using controlled experimental designs and investigating multiple dimensions of niche partitioning simultaneously. Finally, we recommend complementing the coefficient of temporal overlap with other metrics of fine‐scale spatiotemporal interactions.

Satellite Remote Sensing and the Marine Biodiversity Observation Network: Current Science and Future Steps

Coastal ecosystems are rapidly changing due to human-caused global warming, rising sea level, changing circulation patterns, sea ice loss, and acidification that in turn alter the productivity and composition of marine biological communities. In addition, regional pressures associated with growing human populations and economies result in changes in infrastructure, land use, and other development; greater extraction of fisheries and other natural resources; alteration of benthic seascapes; increased pollution; and eutrophication. Understanding biodiversity is fundamental to assessing and managing human activities that sustain ecosystem health and services and mitigate humankind’s indiscretions. Remote-sensing observations provide rapid and synoptic data for assessing biophysical interactions at multiple spatial and temporal scales and thus are useful for monitoring biodiversity in critical coastal zones. However, many challenges remain because of complex bio-optical signals, poor signal retrieval, and suboptimal algorithms. Here, we highlight four approaches in remote sensing that complement the Marine Biodiversity Observation Network (MBON). MBON observations help quantify plankton functional types, foundation species, and unique species habitat relationships, as well as inform species distribution models. In concert with in situ observations across multiple platforms, these efforts contribute to monitoring biodiversity changes in complex coastal regions by providing oceanographic context, contributing to algorithm and indicator development, and creating linkages between long-term ecological studies, the next generations of satellite sensors, and marine ecosystem management.

Recovery trajectories and community resilience of biofilms in receiving rivers after wastewater treatment plant upgrade

Wastewater treatment plant (WWTP) upgrades can reduce both nutrient and micropollutant emissions into receiving rivers, thus modifying the composition and function of biological communities. However, how microbial communities vary and whether they can be restored to levels found in less-polluted rivers remains uncertain. Aquatic biofilms are sensitive to environmental change and respond rapidly to bottom-up pressure. Thus, we used 12 flumes configured in three experimental treatments to mimic the dynamic processes of biofilm microbial communities occurring in a wastewater-receiving river following WWTP upgrade, with rivers containing two levels of nutrients and micropollutants used as references. We compared the biofilm microbial biomass, carbon source utilization, and community composition among the three “blocks”. Results showed that the metabolic patterns of the carbon sources and composition of the biofilm bacterial communities in the flumes mimicking a receiving river with WWTP upgrade recovered over time to those mimicking a less-disturbed river. The restoration of potential carboxylic acid-consuming denitrifying bacteria (i.e., Zoogloea, Comamonas, Dechloromonas, and Acinetobacter) likely played a significant role in this process. Combining quantitative analysis of the denitrification genes nirS and nosZ, we confirmed that the denitrification function of the river biofilms recovered after WWTP upgrade, consistent with our previous field investigation.

From microbes to mammals: agriculture homogenizes pond biodiversity across different land-use types

The diversity and composition of biological communities in ecosystems is typically linked to land use. Consequently, intensive agriculture has a strong influence on these patterns, including a reduction and homogenization of species diversity. Kettle holes (KH; also known as potholes) are small water bodies (<1 ha) typical to formerly glaciated land on the northern hemisphere, reaching densities up to several dozen per km2. They often function as drainage centers, linking various landscape elements in their surroundings and are hotspots of aquatic biodiversity in terrestrial landscapes. In the 1950s, the land use surrounding KH in Europe (e.g., Germany, Poland, The Netherlands) and North America (USA and Canada) shifted towards intensive agriculture, likely affecting the local and regional biodiversity of the KH. Reports on the biodiversity of ponds in agricultural landscapes are scarce, and mostly focus on single taxa. We used deep eDNA amplicon sequencing of eukaryotic, bacterial, and archaeal SSU rRNA genes to assess effects of land use on the overall species biodiversity of 67 KH in either arable fields, grasslands, or forests, all embedded in a landscape subjected to intensive agriculture for decades. These were later contrasted with Berlin city ponds. Metatranscriptomic analyses were conducted in parallel to investigate the taxonomic diversity and functionality of the active communities. The amplicon data, >300 million reads, were analyzed with phyloFlash and Kraken2 using the SILVA_SSU_Ref database. Subsequently, the sequences were grouped based on taxonomy. The use of different annotation pipelines resulted in similar patterns. A subset of the data was analyzed using DADA2, generating amplicon sequence variants. Clustering the sequences as variants or according to taxonomy resulted in identical patterns, suggesting that broad taxonomical groupings provide sufficient resolution for general overviews. Annotation of the eukaryotic community was challenging, as none of the currently available databases contains sufficient high-quality sequences to cover the entire phylogenetic breadth. To overcome this limitation, we used the SILVA_SSU_Parc database, which also contains short sequences excluded from SILVA_SSU_Ref, thus extending the taxonomic base of the analysis. The curated, high-quality PR2 eukaryotic database did not provide better results than the SILVA_SSU_Ref database. An incompatibility between the SILVA and classical taxonomic nomenclature resulted in a ‘language barrier,’ which could be partly resolved by using the parallel EMBL taxonomy provided in the SILVA databases. Nevertheless, we propose that short-read SSU-based eukaryotic taxonomic annotations should be validated by other means. Despite such methodological limitations, our study demonstrates that deep amplicon sequencing of eDNA return a reliable picture of the biodiversity in complex ecosystems. Such information is sufficient to identify biodiversity patterns across the three domains of life and can serve to pinpoint taxonomic groups which should be investigated by a more detailed approach. Our study concluded that long-term exposure to intensive agriculture results in biodiversity homogenization across diverse taxonomic groups, removing most differences in biodiversity patterns among land-use types. This outcome contrasts with biodiversity patterns associated with sediments of the KH, where temporal coverage by the eDNA analyses extends back to at least the onset of intensive agriculture. However, metatranscriptomic analyses, reflecting the distribution of activities rather than relative abundance, revealed temporal differences in the structure of the active community in KH of the investigated land-use types, matching times of field fertilization. Thus, even in a landscape where biodiversity has been homogenized, inputs from the surroundings result in short-term activity changes of different organisms. This needs to be considered when developing new management schemes needed to counteract the current biodiversity loss.

Nitrogen-induced acidification plays a vital role driving ecosystem functions: Insights from a 6-year nitrogen enrichment experiment in a Tibetan alpine meadow

Anthropogenic nitrogen (N) input has overtaken natural N fixation as the leading source of reactive N, and can profoundly alter the structure and functions of terrestrial ecosystems. N input impacts ecosystem functions through altering abiotic (e.g., soil nutrients and pH) and biotic (e.g., biological community composition) properties, but the relative importance of these abiotic and biotic effects remains largely unknown. We conducted a 6-year experiment of N manipulations (0, 5, 10, and 20 g N m−2 yr−1) in a Tibetan alpine meadow to assess N-induced abiotic and biotic effects on ecosystem functions. A complementary experiment with acid additions (0, 0.66, 2.65, 4.63, and 7.28 mol H+ m−2 yr−1) was also carried out to examine the direct impact of acidification. We found that N enrichment significantly increased plant productivity but decreased soil microbial respiration. While the increased productivity was associated with increased N availability, the reduction in soil microbial respiration was mainly explained by the decreased soil pH. In the acid addition experiment, enhanced soil acidity due to the increased proton concentration significantly reduced soil microbial respiration. These results indicate that N-induced changes in soil pH represent an important mechanism driving the ecosystem functions, suggesting that N-induced acidification should receive more attention for understanding and predicting ecosystem services under future N-enrichment scenarios.

Seasonal and annual variability in daily vertical migration observed from acoustic Doppler current profiler derived backscatter at the Mid-Atlantic Bight shelf break

75 kHz ADCPs stationed near the 450-meter isobath within the Ocean Observatories Initiative Coastal Pioneer Array capture consistent patterns indicative of daily vertical migration (DVM) in depth profiles of both mean volume backscatter (MVB) and the vertical component of velocity (w). While the presence of DVM patterns is consistent throughout 2018 and 2019, attributes of MVB and w profiles are subject to variability within and across different seasons and years. This variability may be influenced by abiotic factors characteristic of the Mid-Atlantic Bight region such as the disruption of typical spring time temperature-salinity structures via frontal instability or the episodic introduction of warm-core rings. Additionally, biological community composition in the region may be reflected in MVB and w profiles given zooplankton survey data and knowledge of seasonal biophysical dynamics in the region, along with measured variability of other environmental properties observed by the Pioneer Array including dissolved oxygen concentration, chlorophyll-a concentration, and photosynthetically available radiation. Linking all of these factors, driven by long-term, stationary acoustical observations, can provide a useful framework for more directly assessing the impacts of aberrational physical phenomena on regional biological patterns.

Coral reef benthic community structure is associated with the spatiotemporal dynamics of submarine groundwater discharge chemistry

AbstractSubmarine groundwater discharge (SGD) is an important transporter of solutes and fresh water in coastal systems worldwide. In high island systems with a mixed semidiurnal tidal cycle driving SGD, coastal biogeochemistry is temporally and spatially variable. Past studies have shown that SGD covaries with the local species composition, diversity, and richness of biological communities on a scale of meters. Empirical orthogonal function analyses (EOF)—a method analogous to principal components analysis which finds spatial patterns of variability and their time variation period—were used to define both the spatial and temporal variation in SGD using spatially resolved time series of salinity. The first two EOFs represented variability at the tidal 12‐h period and the daily 24‐h period, respectively, and were responsible for more than 50% of the SGD‐derived salinity variability. We used the first two EOFs to explore spatiotemporally explicit patterns in SGD variability and their relationships with benthic community structure in reef systems. Distance‐based linear models found significant relationships between multivariate community structure and variability in SGD at different periods. Taxa‐specific logistic regressions showed that zoanthids and turf are more likely to be present in areas with high tidally driven SGD variability, while the inverse relationship is true for the invasive rhodophyte Acanthophora spicifera, calcifying macroalgae, the native rhodophyte Pterocladiella sp., the cyanobacteria Lyngbya sp., and the invasive chlorophyte Avrainvillea amadelpha. These results show that benthic communities vary with respect to SGD derived salinity at the scale of hundreds of meters resulting in spatially heterogeneous biotic patches.

Variable niche breadth in benthic diatoms: Implications of ecological specialization and generalization for community structure

The mechanisms that regulate the composition and structure of biological communities remain poorly understood. Diatom communities have traditionally been assumed to be a collection of r-selected, ecologically redundant generalist taxa with distributions constrained largely by dispersal limitation. Here, we challenge this notion by presenting a novel model that uses distributional data to estimate ecological specialization for groups of diatom taxa. We further develop this model to evaluate relationships among ecological specialization, taxonomic richness, and species’ abundance using field data collected from ancient Lake Matano and the broader Malili Lakes system (Sulawesi, Indonesia), as well as Mazinaw Lake (Ontario, Canada). We demonstrated that diatom niche breadth is highly variable both at the assemblage scale and among genera within assemblages. Ecologically-specialized genera exhibited higher taxonomic richness than their generalist counterparts, suggesting that ecological specialization serves to support the sympatric coexistence of multiple species by limiting competitive interactions among congeneric taxa. This assertion is further supported by species’ abundance patterns, which suggested that resources are evenly partitioned among taxa within specialist genera, while less-specialized genera are composed of taxa with either exceptionally high or exceptionally low abundances reflective of their relative success in competitive interactions with one another. Our findings indicate that the often-overlooked complement of rare taxa within diatom assemblages are in fact the entities that respond most sensitively to environmental conditions and are worthy of far greater consideration in environmental assessment and paleolimnological studies.

Comparing taxon- and trait-environment relationships in stream communities

Abstract Traits define how organisms interact with their surrounding environment and with other organisms. Thus, trait composition of biological communities is expected to change predictably along environmental gradients. Because organisms’ traits, but not taxonomic identity, determine their fitness, trait-environment relationships should provide a better way to elucidate how biodiversity respond to environmental change. Here, we used data on tropical streams embedded in a landscape of intensive agriculture to investigate trait-environment and taxon-environment relationships in a set of 91 mayfly communities from southeastern Brazil. We expected that trait-environment relationships would be stronger than taxon-environment relationships and that the linkage between traits and environmental variables would provide mechanistic insights on environmental filtering. We found that variation in both species composition and traits were correlated to salinity, highlighting the influence of water salinization on mayfly communities due to agricultural practices. Surprisingly, using analogous statistical methods, in general, we found that the strengths of trait-environment relationships were lower than that of taxon-environment relationships. Further, (1) species responses to gradients were not correlated to similarity in their traits and (2) some species with different trait composition responded similarly to environmental variation, indicating that different suite of traits can cope with similar environmental contexts. Besides some cautionary results about trait-based approaches, results from taxon-based approaches indicated that variation in composition was more related to spatial variables, suggesting that dispersal limitation undermine its use for large scale assessments. Our results suggest that both taxon- and trait-based approaches have weakness and strengths and deciding between them for biomonitoring purposes will depend on spatial scales, trait interrelationships, and analytical methods.

A comparative study of macroinvertebrate biodiversity in highway stormwater ponds and natural ponds

The use of stormwater ponds along the highways is shown to be an effective alternative to conventional systems, which are usually sewers. These ponds have the potential to combine their primary function of pollution and peak flow control with the promotion of biodiversity. The present study focuses on comparing natural and highway stormwater ponds in terms of environmental conditions and biodiversity of macroinvertebrate communities. Twelve highway stormwater ponds and nineteen natural ponds (located within or in the vicinity of cultivated landscape) were explored for the number of taxa, community composition, and selected environmental variables: pH, conductivity, pond surface area, the number of ponds within 1 km radius, and the distance to nearest neighboring pond. Highway stormwater ponds showed much higher conductivity, which is a good proxy for chloride concentration and highway pollutants. In addition, the surface area of stormwater ponds was almost twice as big as that of natural ponds. The biological community composition was very different between the two types of ponds, and the number of taxa was slightly higher in the highway stormwater ponds. The most important variables responsible for the variation in the biological community composition were conductivity, pond surface area, and the number of ponds within 1 km radius. This study supports that, in addition to their role in pollution and peak flow control, stormwater ponds have the potential to provide a habitat that may otherwise be unavailable along the highway.

Assessing the hierarchy of long-term environmental controls on diatom communities of Yellowstone National Park using lacustrine sediment records

Chraïbi VLS, Fritz SC. 2020. Assessing the hierarchy of long-term environmental controls on diatom communities of Yellowstone National Park using lacustrine sediment records. Lake Reserv Manage. 36:278–296.An ecosystem’s ability to maintain structure and function following disturbance, defined as resilience, is influenced by a hierarchy of environmental controls, including climate, surface cover, and ecological relationships that shape biological community composition and productivity. This study examined lacustrine sediment records of naturally fishless lakes in Yellowstone National Park to reconstruct the response of aquatic communities to climate and trophic cascades from fish stocking. Sediment records of diatom algae did not exhibit a distinct response to fish stocking in terms of assemblage or algal productivity. Instead, 3 of 4 lakes underwent a shift to dominance by benthic diatom species from 1935 to 1950, which suggests lower lake levels resulting from warmer, drier climatic conditions. The lake that did not undergo such a shift is fed by groundwater rather than snowmelt, suggesting a buffering effect by water source. Dissimilarity analysis shows that the diatom assemblages in all 4 lakes have become increasingly dissimilar since circa 1955, suggesting that communities have not yet stabilized from the first-order influence of climate. Thus, climate likely had a more prominent influence on diatom community structure than did manipulation of the fish community. Understanding the relative importance and interplay among abiotic and biotic stressors and the resultant resilience of an ecosystem provides implications for the adaptive management of lakes.

High-throughput sequencing for community analysis: the promise of DNA barcoding to uncover diversity, relatedness, abundances and interactions in spider communities

Large-scale studies on community ecology are highly desirable but often difficult to accomplish due to the considerable investment of time, labor and, money required to characterize richness, abundance, relatedness, and interactions. Nonetheless, such large-scale perspectives are necessary for understanding the composition, dynamics, and resilience of biological communities. Small invertebrates play a central role in ecosystems, occupying critical positions in the food web and performing a broad variety of ecological functions. However, it has been particularly difficult to adequately characterize communities of these animals because of their exceptionally high diversity and abundance. Spiders in particular fulfill key roles as both predator and prey in terrestrial food webs and are hence an important focus of ecological studies. In recent years, large-scale community analyses have benefitted tremendously from advances in DNA barcoding technology. High-throughput sequencing (HTS), particularly DNA metabarcoding, enables community-wide analyses of diversity and interactions at unprecedented scales and at a fraction of the cost that was previously possible. Here, we review the current state of the application of these technologies to the analysis of spider communities. We discuss amplicon-based DNA barcoding and metabarcoding for the analysis of community diversity and molecular gut content analysis for assessing predator-prey relationships. We also highlight applications of the third generation sequencing technology for long read and portable DNA barcoding. We then address the development of theoretical frameworks for community-level studies, and finally highlight critical gaps and future directions for DNA analysis of spider communities.