Gradient In Species Richness Research Articles

Variation in diversity-function relationships can be explained by species interactions.

Research Highlight: Wu, D., Xu, C., Wang, S., Zhang, L., & Kortsch, S. (2022). Why are biodiversity-ecosystem functioning relationships so elusive? Trophic interactions may amplify ecosystem function variability. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13808. There is consensus that average trends of ecosystem functions increase with species diversity. However, large variations in ecosystem function (VEF) in systems with similar diversity levels are commonly observed, yet not understood. In this study, Wu et al. (2022) integrate empirical aquatic food webs with a multitrophic model to show that VEF generally shows a hump-shaped pattern along the species richness gradient. This pattern is related to changes in taxa composition across trophic levels-the proportion of consumer species relative to basal species-along the gradient of species richness. Thus, VEF dependence on species diversity is driven by both bottom-up and top-down control that regulate taxa composition and taxa dominance. These results are corroborated with an independent food web dataset from the Gulf of Riga. An important implication of this study is that biodiversity loss may not only reduce the mean levels of ecosystem functioning, but also increase unpredictability of functions by generating greater function variability.

Abiotic and biotic drivers of tree trait effects on soil microbial biomass and soil carbon concentration

AbstractForests are ecosystems critical to understanding the global carbon budget, due to their carbon sequestration potential in both aboveground and belowground compartments, especially in species‐rich forests. Soil carbon sequestration is strongly linked to soil microbial communities, and this link is mediated by the tree community, likely due to modifications of microenvironmental conditions (i.e., biotic conditions, soil properties, and microclimate). We studied soil carbon concentration and the soil microbial biomass of 180 local neighborhoods along a gradient of tree species richness ranging from 1 to 16 tree species per plot in a Chinese subtropical forest experiment (BEF‐China). Tree productivity and different tree functional traits were measured at the neighborhood level. We tested the effects of tree productivity, functional trait identity, and dissimilarity on soil carbon concentrations, and their mediation by the soil microbial biomass and microenvironmental conditions. Our analyses showed a strong positive correlation between soil microbial biomass and soil carbon concentrations. In addition, soil carbon concentration increased with tree productivity and tree root diameter, while it decreased with litterfall C:N content. Moreover, tree productivity and tree functional traits (e.g., fungal root association and litterfall C:N ratio) modulated microenvironmental conditions with substantial consequences for soil microbial biomass. We also showed that soil history and topography should be considered in future experiments and tree plantations, as soil carbon concentrations were higher at sites where historical (i.e., at the beginning of the experiment) carbon concentrations were high, themselves being strongly affected by the topography. Altogether, these results implied that the quantification of the different soil carbon pools is critical for understanding microbial community–soil carbon stock relationships and their dependence on tree diversity and microenvironmental conditions.

Patterns of functional diversity along latitudinal gradients of species richness in eleven fish families

AbstractAimAs we enter an era of major biodiversity shifts, understanding large‐scale biodiversity patterns has become crucial for ecological and conservation purposes. Often, conservation priorities are based on concepts derived largely from species richness, yet recent work shows that different facets of biodiversity are also crucial for proper ecosystem continuity, function and services. One facet of biodiversity increasingly relevant to conservation is functional diversity. Here, we aim to improve our understanding of large‐scale patterns of biodiversity by testing the hypothesis that species richness can also accurately estimate functional diversity along the latitudinal gradient of species richness in fish.LocationMarine environments.Time periodContemporary.Major taxa studiedEight hundred and forty‐two species within 11 fish families: Acanthuridae, Blenniidae, Chaetodontidae, Gobiidae, Labridae, Lutjanidae, Pleuronectidae, Pomacanthidae, Pomacentridae, Scombridae and Sparidae.MethodsUsing geometric morphometrics to calculate morphological diversity, a proxy for functional diversity, we estimated the expected functional diversity for a given number of species and compared it with the observed functional diversity in fish families along latitudes. We then fitted a broken‐stick regression model with estimates of functional diversity over absolute degree of latitudes to locate latitudes where significant shifts in functional diversity occur.ResultsWe found that species richness typically over‐ or underestimated functional diversity along the latitudinal gradient of species richness in the evaluated fishes. We also showed that for most families investigated, there was a pattern of stable functional diversity from the equator through the tropics that shifted, with a mean inflection point occurring at absolute latitude 31.7 ± 10.1°. We suggest that this pattern might be linked to changes in environmental factors such as global temperature and/or habitat availability beyond tropical latitudes; however, these concepts require more study.Main conclusionsThis analysis shows the importance of considering functional diversity further, in combination with other biodiversity metrics, when developing conservation priorities and policies.

松嫩平原湿地植物群落多样性的环境梯度分布格局及控制因子

PDF HTML阅读 XML下载 导出引用 引用提醒 松嫩平原湿地植物群落多样性的环境梯度分布格局及控制因子 DOI: 10.5846/stxb202201150145 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校自主科研项目计划（2572019DF07） Environmental gradient distribution patterns of wetland plant community diversity and controlling factors in Songnen Plain Author: Affiliation: Fund Project: Supported by: The Independent Research Project of the Central Universities of China (2572019DF07) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:物种丰富度格局及其决定因素是生态学核心问题，但对其形成机制仍缺乏共识。为探究松嫩平原西部半干旱区沿湖岸至高地环境梯度（局地尺度）植物群落多样性分布格局及其决定因素，以沿该梯度依次分布的7种群落（狭叶香蒲沼泽、小香蒲沼泽、芦苇沼泽、草丛沼泽、拂子茅草甸、羊草草甸和榆树疏林）为对象，采用样带网格调查法及聚类分析法划分群落类型，测定物种丰富度、α多样性和β多样性及其环境因子（水位、土壤含水率、有机质等），揭示群落多样性空间分布规律及其形成机制。结果表明，沿湖岸至高地环境梯度：（1）物种丰富度（2.00-18.00）和α多样性（Simpson指数0.12-0.90；Shannon-Wiener指数0.23-2.57和Pielou指数0.34-0.88）总体上均呈类似N字型分布（在下部深水生境狭叶香蒲沼泽最低、中下部季节性积水生境草丛沼泽最高、中上部湿润生境拂子茅草甸较低、上部沙丘干旱生境榆树疏林又较高）；（2）广义的β多样性（Jaccard指数0.56-0.96）可以分解成物种周转（丰富度没有变化的地点间的物种替代）和嵌套（物种贫乏地点是物种丰富地点子集时的物种差异）两个过程，其在该梯度上半段干旱生境和下半段浅水生境相对较高，且主要由周转过程控制。在常年积水生境上最低且仅由嵌套过程控制，而在环境梯度中间地段则由周转和嵌套过程共同控制；（3）物种丰富度和α多样性的主控因子沿该梯度发生了明显转换，在高水位区由水位、有机质和全磷共同控制；中水位区仅由速效磷控制；低水位区由pH和含水率控制。因此，松嫩平原半干旱区沿湖岸至高地环境梯度物种丰富度和α多样性存在明显的空间分布格局及具有较高的β多样性，且其主要形成机制为微地形创造局地空间环境异质性与物种库相互作用共同塑造了植物群落多样性，故在生物多样性管理实践中应对其空间分布格局完整性加以重点保护。 Abstract:Patterns and determinants of species richness are the central issues in ecology, but there is still a lack of consensus on their formation mechanisms. In order to explore the distribution patterns and determinants of community diversity along lakeshore-highland environmental gradient (local scale) in western Songnen Plain semi-arid region, species richness, α diversity, β diversity and environmental factors including water level (WL), soil water content (WC), organic matter (OM), etc. were measured by setting up sample belts and cluster analysis in seven communities (Typha angustifolia wetland, Typha minima wetland, Phragmites australis wetland, hassock wetland, Calamagrostis epigeios meadow, Leymus chinensis meadow and elm sparse forest) along this gradient, to reveal the spatial variation and formation mechanisms of community diversity. The results show that, along lakeshore-highland environmental gradient:(1) both species richness (2.00-18.00) and α diversity (Simpson index 0.12-0.90; Shannon-Wiener index 0.23-2.57 and Pielou index 0.34-0.88) showed a similar N-shaped distribution pattern (Typha angustifolia wetland was the lowest at the lower deep-water habitats, hassock wetland was the highest at the lower-middle seasonal inundated habitat, the lower at the middle-upper wet habitats of Calamagrostis epigeios meadow and the higher at the upper arid habitats of dune elm sparse forest). (2) We partitioned the generalized β diversity (Jaccard index 0.56-0.96) into two components:species turnover (species replacement among sites without changes in richness) and nestedness (species differences among sites when species-poor sites constitute subsets of those with a greater number of taxa). β diversity was relatively high at arid habitats located in upper half and shallow-water habitat located in lower half of the gradient, and it was mainly controlled by turnover processes. At the permanently inundated habitats, it was the lowest one, which is controlled only by nestedness processes. But in the middle of the environmental gradient, the turnover and nestedness processes control it togther. (3) The main controlling factors of species richness and α diversity were significantly converted along the gradient. The high water level area was jointly controlled by water level, organic matter and total phosphorus (TP), the medium water level area was controlled only by available phosphorus (AP) and the low water level area was jointly controlled by pH and water content. Therefore, there were obviously spatial distribution patterns of species richness and α diversity, and higher β diversity along lakeshore-highland environmental gradient in the Songnen Plain semi-arid region. Our results suggested that the main mechanism was the interaction between the local spatial environmental heterogeneity created by microtopography and the region species pool, which jointly shaped the plant community diversity. Thus, its spatial distribution patterns integrity should be protected in the practice of biodiversity management. 参考文献 相似文献 引证文献

Precipitation and potential evapotranspiration determine the distribution patterns of threatened plant species in Sichuan Province, China

A fundamental goal of ecologists is to determine the large-scale gradients in species richness. The threatened plants are the priority of such studies because of their narrow distribution and confinement to a specific habitat. Studying the distribution patterns of threatened plants is crucial for identifying global conservation prioritization. In this study, the richness pattern of threatened plant species along spatial and elevation gradients in Sichuan Province of China was investigated, considering climatic, habitat-heterogeneity (HHET), geometric constraint and human-induced factors. The species richness pattern was analyzed, and the predictor variables, including mean annual temperature (MAT), mean annual precipitation (MAP), potential evapotranspiration (PET), HHET, and disturbance (DIST), to species richness were linked using the geographical distribution data of threatened species compiled at a spatial resolution of 20 km × 20 km. Generalized linear models and structural equation modelling were used to determine the individual and combined effects of each variable on species richness patterns. Results showed a total of 137 threatened plant species were distributed between 200 and 4800 m.a.s.l. The central region of the province harbors the highest species diversity. MAP and PET profoundly explained the richness pattern. Moreover, the significant role of DIST in the richness patterns of threatened plants was elucidated. These findings could help determine the richness pattern of threatened plant species in other mountainous regions of the world, with consideration of the impact of climate change.

Drivers of species richness and beta diversity of fishes in an Afrotropical intermittent river system.

Tropical freshwater ecosystems are some of the most threatened systems yet remain understudied relative to temperate systems. Here, we look at the drivers of community structure of fishes in a tropical and intermittent system in central Kenya. We conducted monthly sampleswithin the upper Northern Ewaso Ng'iro to assess variation in community composition and abiotic characteristics. We analyzed species richness along the longitudinal gradient, computed beta diversity within the system, relative contributions of each site, and partitioned beta diversity metrics into nestedness and turnover components. We found that, similar to temperate intermittent systems, species richness varied along the longitudinal gradient, nestedness contributions to beta diversity exceeded those of turnover, and environmental and spatial variables determined patterns of beta diversity. Sites at the highest and lowest ends of the species richness gradient showed the highest contributions to beta diversity, suggesting sites important for preservation or restoration initiatives, respectively. With ongoing water extraction and conflict over resources throughout the region, this study highlights the need for further investigations of the effects of multiple stressors on biodiversity patterns and ecosystem functioning in tropical stream communities.

Community biomass is driven by dominants and their characteristics – The insight from a field biodiversity experiment with realistic species loss scenario

Abstract Revealing the role of biodiversity in ecosystem functioning (BEF) has been a major focus of ecological research over recent decades. In general, results from artificially assembled communities point to the important role of biodiversity showing that loss of species has a negative effect on various ecosystem functions (mostly assessed by above‐ground peak biomass). However, the evidence from manipulations of natural communities is scarce, and results are often contradictory between these two approaches. In particular, the importance of species dominance for ecosystem functioning remains poorly understood. We created a gradient of plant species richness in a meadow community following a realistic species loss scenario (removal of less abundant species) to test the effect of diversity on community biomass and assess the importance of subordinate species compared with dominants in a 5‐year experiment. Contrasting with results of BEF experiments with artificial assembly, we did not find any relationship between plant species diversity and above‐ground biomass across the timeframe of the experiment. We provide evidence that dominant species' identity and traits are the main drivers of community biomass because dominant species were able to maintain biomass production after substantial species loss. Furthermore, dominants prevented community biomass from declining and biomass was indirectly influenced not by species richness but through differences in functional diversity. Our results support the mass ratio hypothesis, showing much bigger effect of dominant species on community biomass production and hints to the rather minor importance of the complementarity effect between species. We emphasize that BEF research should more focus on the role of dominant species in maintaining various ecosystem functions. Synthesis. Species diversity is a poor predictor of community above‐ground biomass production and dominant species can effectively compensate the total production after substantial loss of other species in a grassland community.

Precipitation drives species accumulation whereas temperature drives species decline in Himalayan vertebrates

AbstractAimMany studies have explored taxon‐specific richness patterns with elevation, but few have concurrently evaluated different mechanisms to explain elevational patterns across multiple taxa. We used a novel, cross‐taxa approach to study species richness patterns combined with a framework that tests drivers of species accumulation versus decline along the elevational gradient in the Himalayas.LocationThe Himalayas.TaxonMammals, birds and amphibians.MethodsWe used geographical and elevational data of 314 mammals, 842 breeding birds and 147 amphibians to investigate species richness patterns across elevational and geographical spaces. We divided the elevational species richness gradient into segments of species accumulation versus species decline by piecewise linear regressions. We used path analysis to disentangle the direct and indirect effects of the predictors on species richness for the overall pattern and its divided segments. We test the asymmetry of main drivers between the accumulation and decline segments of richness by iteration procedure.ResultsSpecies richness for most taxa tracks an elevational hump‐shaped distribution. The dominant driver of the overall pattern varied by taxa and in context to subregion. Across taxa, precipitation best predicts the accumulation of species richness, whereas temperature best predicts the decline in species richness. Moreover, temperature and precipitation can affect species richness indirectly through productivity, showcasing a large interactional effect of climate and productivity on species richness.Main conclusionsResource allocation of the ecosystem and requirements of the species differ between the lower and upper elevation segments but remain consistent across the overall gradient. The resources essential for promoting diversity and mediating stochastic processes are directly tied to precipitation at the process of species accumulation and temperature at the process of species richness decline. Our findings support the existing theory in climate change science that reduced precipitation combined with increasing temperature may cause species extinction in the species‐rich lowlands.

Mapping species diversification metrics in macroecology: Prospects and challenges

The intersection of macroecology and macroevolution is one of today’s most active research in biology. In the last decade, we have witnessed a steady increment of macroecological studies that use metrics attempting to capture macroevolutionary processes to explain present-day biodiversity patterns. Evolutionary explanations of current species richness gradients are fundamental for understanding how diversity accumulates in a region. Although multiple hypotheses have been proposed to explain the patterns we observe in nature, it is well-known that the present-day diversity patterns result from speciation, extinction, colonization from nearby areas, or a combination of these macroevolutionary processes. Whether these metrics capture macroevolutionary processes across space is unknown. Some tip-rate metrics calculated directly from a phylogenetic tree (e.g., mean root distance -MRD-; mean diversification rate -mDR-) seem to return very similar geographical patterns regardless of how they are estimated (e.g., using branch lengths explicitly or not). Model-based tip-rate metrics —those estimated using macroevolutionary mixtures, e.g., the BAMM approach— seem to provide better net diversification estimates than only speciation rates. We argue that the lack of appropriate estimates of extinction and dispersal rates in phylogenetic trees may strongly limit our inferences about how species richness gradients have emerged at spatial and temporal scales. Here, we present a literature review about this topic and empirical comparisons between select taxa with several of these metrics. We implemented a simple null model approach to evaluate whether mapping of these metrics deviates from a random sampling process. We show that phylogenetic metrics by themselves are relatively poor at capturing speciation, extinction, and dispersal processes across geographical gradients. Furthermore, we provide evidence of how parametric biogeographic methods can improve our inference of past events and, therefore, our conclusions about the evolutionary processes driving biodiversity patterns. We recommend that further studies include several approaches simultaneously (e.g., spatial diversification modeling, parametric biogeographic methods, simulations) to disentangle the relative role of speciation, extinction, and dispersal in the generation and maintenance of species richness gradients at regional and global scales.

Variations in Functional Richness and Assembly Mechanisms of the Subtropical Evergreen Broadleaved Forest Communities along Geographical and Environmental Gradients

Linking functional trait space and environmental conditions can help to understand how species fill the functional trait space when species increase along environmental gradients. Here, we examined the variations in functional richness (FRic) and their correlations with key environmental variables in forest communities along latitudinal, longitudinal, and elevational gradients, by measuring seven functional traits of woody plants in 250 forest plots of 0.04 ha across five locations in the subtropical evergreen broadleaved forests (SEBLF) of China. On this basis, we explored whether environmental filtering constrained the functional volume by using a null model approach. Results showed that FRic decreased with increasing elevation and latitude, while it increased with increasing longitude, mirroring the geographical gradients in species richness. FRic was significantly related to precipitation of driest quarter, soil pH, and total phosphorus. Negative SES.FRic was prevalent (83.2% of the communities) in most SEBLF communities and was negatively related to mean diurnal range. Our study suggested that the geographical variation in the functional space occupied by SEBLF communities was affected mainly by climate and soil conditions. The results of the null model revealed that niche packing was dominant in SEBLF communities, highlighting the importance of environmental filtering in defining functional volume within SEBLF communities.

A framework for quantifying soundscape diversity using Hill numbers

Abstract Soundscape studies are increasingly used to capture landscape‐scale ecological patterns. Yet, several aspects of soundscape diversity remain unexplored. Although some processes influencing acoustic niche usage may operate in the 24‐hr temporal domain, most acoustic indices only capture the diversity of sounds co‐occurring in sound files at a specific time of day. Moreover, many indices do not consider the relationship between the spectral and temporal traits of sounds simultaneously. To provide novel insights into landscape‐scale patterns of acoustic niche usage at broader temporal scales, we present a workflow to quantify soundscape diversity through the lens of trait‐based ecology. Our workflow quantifies the diversity of sound in the 24‐hr acoustic trait space. We introduce the Operational Sound Unit (OSU), a unit of diversity measurement that groups sounds by their shared acoustic properties. Using OSUs and building on the framework of Hill numbers, we propose three metrics that capture different aspects of acoustic trait space usage: (i) soundscape richness, (ii) soundscape diversity and (iii) soundscape evenness. We demonstrate the use of these metrics by (a) simulating soundscapes to assess whether the indices possess a set of desirable behaviours and (b) quantifying soundscape richness and evenness along a gradient in species richness. We demonstrate that (a) the indices outlined herein have desirable behaviours and (b) the soundscape richness and evenness are positively correlated with the richness of sound‐producing species. This suggests that more acoustic niche space is occupied when the species richness is higher. Additionally, species‐poor acoustic communities have a higher proportion of rare sounds and use the acoustic space less evenly. Our workflow generates novel insights into acoustic niche usage at a landscape scale and provides a useful tool for biodiversity monitoring. Moreover, Hill numbers can also be used to measure the taxonomic, functional and phylogenetic diversity. Using a common framework for diversity measurement gives metrics a common behaviour, interpretation and standardised unit, thus ensuring comparisons between soundscape diversity and other metrics represent real‐world ecological patterns rather than mathematical artefacts stemming from different formulae.

Effects of Plasticity on Elevational Range Size and Species Richness.

AbstractElevational ranges within many taxa are greater in the north temperate region than the tropics. Two hypotheses to explain the pattern are, first, that large elevational ranges in the temperate region arise because species have evolved broad tolerance curves in response to seasonality and, second, that a low diversification rate in the temperate region (speciation minus extinction) has led to relatively few species, each of which occupies a large elevational range in the absence of competitors (character release). We build a quantitative genetic model of selection on a phenotypic trait, whereby increased tolerance is modeled as arising from plasticity in the trait. We show that broad tolerances result in evolution of large elevational ranges because they induce shallower genotypic clines and hence reduced maladaptive gene flow. The evolution of large elevational ranges results in relatively few competing species arranged along the elevational gradient at a species carrying capacity. In such saturated communities, species have much elevational overlap. In contrast, in similar-sized communities that could accommodate many more species, the resulting character release is associated with smaller elevational overlaps. Empirical assessment of these predictions should contribute to assessing any role for ecological limits in driving the latitudinal diversity gradient in species richness.

Global variation in diversification rate and species richness are unlinked in plants

Species richness varies immensely around the world. Variation in the rate of diversification (speciation minus extinction) is often hypothesized to explain this pattern, while alternative explanations invoke time or ecological carrying capacities as drivers. Focusing on seed plants, the world's most important engineers of terrestrial ecosystems, we investigated the role of diversification rate as a link between the environment and global species richness patterns. Applying structural equation modeling to a comprehensive distribution dataset and phylogenetic tree covering all circa 332,000 seed plant species and 99.9% of the world's terrestrial surface (excluding Antarctica), we test five broad hypotheses postulating that diversification serves as a mechanistic link between species richness and climate, climatic stability, seasonality, environmental heterogeneity, or the distribution of biomes. Our results show that the global patterns of species richness and diversification rate are entirely independent. Diversification rates were not highest in warm and wet climates, running counter to the Metabolic Theory of Ecology, one of the dominant explanations for global gradients in species richness. Instead, diversification rates were highest in edaphically diverse, dry areas that have experienced climate change during the Neogene. Meanwhile, we confirmed climate and environmental heterogeneity as the main drivers of species richness, but these effects did not involve diversification rates as a mechanistic link, calling for alternative explanations. We conclude that high species richness is likely driven by the antiquity of wet tropical areas (supporting the "tropical conservatism hypothesis") or the high ecological carrying capacity of warm, wet, and/or environmentally heterogeneous environments.

Can functional leaf traits be used for monitoring wetland restoration? A comparison between commonly used monitoring metrics and functional leaf traits

Monitoring is essential to restoration, but the standard metrics used to monitor wetland restoration do not explicitly account for function in plant communities. Functional traits may be a useful addition to the wetland monitoring toolkit, because they can represent aspects of ecosystem functioning that standard metrics may not. Our objective was to determine how abiotic factors that influence wetland community composition and structure relate to both functional leaf traits and standard vegetation monitoring metrics to determine if functional leaf traits could add a functional component to wetland monitoring. We surveyed 66 100-m2 plots in 22 floodplain wetlands in Illinois that were restored between 1997 and 2010. We used plant species data to calculate the mean coefficient of conservatism (mean C) and richness, and collected leaves to determine community weighted means of specific leaf area (SLA) and leaf dry matter content (LDMC) at each plot. Hydrologic data were used to calculate variables related to frequency, depth, and duration of inundation, and soil samples were collected to determine soil pH, organic matter content, and nitrogen and phosphorous content at each plot. We used structural equation models to understand how predictor variables (hydrological variables, soil variables, canopy cover, time since restoration, and latitude) influenced each other, and ultimately how they influenced response variables (mean C, richness, percent non-native species cover, SLA, and LDMC). LDMC and SLA were poorly explained by predictor variables and had relatively few significant relationships within models. Predictor variables best explained variance in mean C, followed by percent non-native cover, richness, then LDMC and SLA. Mean C was positively influenced by canopy cover and negatively influenced by soil fertility, whereas richness was negatively influenced by latitude. There was a strong latitudinal gradient of species richness from north to south, such that southern plots were significantly more diverse and had less cover by non-native species than northern plots. Our research suggests that SLA and LDMC may not be well suited for use as wetland restoration monitoring tools in Midwestern floodplain wetlands, and that monitoring tools already in place may sufficiently reflect abiotic conditions.

The use of citizen science in fish eDNA metabarcoding for evaluating regional biodiversity in a coastal marine region: A pilot study

To test the feasibility of a citizen science program for fish eDNA metabarcoding in coastal marine environments, we recruited six groups of voluntary citizens for a science education course at a natural history museum. We held a seminar on eDNA and a workshop for seawater sampling and on-site filtration using syringes and filter cartridges for the participants. After that, they selected single survey sites following the guidelines for conducting a safe field trip. They performed seawater sampling and on-site filtration at these sites during their summer holidays. The six selected sites unexpectedly included diverse coastal habitats within a 40 km radius, located at temperate latitudes in central Japan (~35°N). After the field trips, they returned filtered cartridges to the museum, and we extracted eDNA from the filters. We performed fish eDNA metabarcoding, along with data analysis. Consequently, we identified 140 fish species across 66 families and 118 genera from the six samples, with species richness ranging from 14 to 66. Despite its limited sample size, such a diverse taxonomic range of fish species exhibited spatial biodiversity patterns within the region, which are consistent with species distribution. These include north-south and urbanization gradients of species richness, geographic structure of the fish communities, and varying salinity preferences of the component species. This case study demonstrates the potential of fish eDNA metabarcoding as an educational and scientific tool to raise public awareness and perform large-scale citizen science initiatives encompassing regional, national, or global fauna.

Moving Toward the Greener Side: Environmental Aspects Guiding Pastoral Mobility and Impacting Vegetation in the Dzungarian Gobi, Mongolia

Livestock grazing often intensifies around herder camps, which can lead to degradation, particularly in arid areas, where vegetation is scarce. In Mongolia, nomadic herders have covered long distances between camps and changed camps regularly for centuries. However, changing socioeconomics, rising livestock numbers, and climatic change have led to growing concerns over rangeland health. To understand travel mobility and livestock grazing patterns, we combined Global Positioning System tracking data of goats, remotely sensing pasture productivity, and ground-based vegetation characteristics in the Great Gobi B Strictly Protected Area, Mongolia. We assessed herder preferences for camp selection, followed 19 livestock herds over 20 months, determined use and nutrient contents of the most dominant plant communities, and estimated plant species richness, vegetation cover, and biomass within different grazing radii around camps. Biomass availability was key for herder decisions to move camps, but in winter, other factors like shelter from wind were more important. Camps were mainly located in Stipa spp. communities, agreeing with herder preferences for this highly nutritious species, and its dominance around camps. Herders changed their camp locations on average 9 times yearly, with a maximum distance of 70–123 km between summer and winter camps, and an average visitation period of 25–49 d per camp, depending on season. Small livestock spent > 13−17 h daily within a radius of 100 m from camp, and livestock use intensity decreased steeply with distance from camp but was remarkably similar around spring, autumn, and winter camps on the Gobi plains. However, we found little evidence for a corresponding gradient in plant species richness, biomass, and cover on the Gobi plains. The high mobility of local herders and the overriding impact of precipitation on pasture dynamics contribute to a sustainable vegetation offtake by livestock in the nonequilibrium rangelands of the Dzungarian Gobi.

Drought soil legacy alters drivers of plant diversity-productivity relationships in oldfield systems.

Ecosystem functions are threatened by both recurrent droughts and declines in biodiversity at a global scale, but the drought dependency of diversity-productivity relationships remains poorly understood. Here, we use a two-phase mesocosm experiment with simulated drought and model oldfield communities (360 experimental mesocosms/plant communities) to examine drought-induced changes in soil microbial communities along a plant species richness gradient and to assess interactions between past drought (soil legacies) and subsequent drought on plant diversity-productivity relationships. We show that (i) drought decreases bacterial and fungal richness and modifies relationships between plant species richness and microbial groups; (ii) drought soil legacy increases net biodiversity effects, but responses of net biodiversity effects to plant species richness are unaffected; and (iii) linkages between plant species richness and complementarity/selection effects vary depending on past and subsequent drought. These results provide mechanistic insight into biodiversity-productivity relationships in a changing environment, with implications for the stability of ecosystem function under climate change.

Robust metagenomic evidence that local assemblage richness increases with latitude in ground‐active invertebrates of North America

Biodiversity monitoring is imperative for understanding how changing climate may impact the distributions of taxa from single species to the spatial distribution of biological diversity. Large‐scale and cross‐taxa biodiversity monitoring also allows an empirical understanding of biogeographic patterns across taxa. One such pattern, where in taxonomic richness peaks at tropical latitudes are typically treated as a biogeographical rule with few notable exceptions. Here we leveraged the invertebrate pitfall collections of the National Ecological Observatory Network (NEON) across North America to describe patterns of local taxonomic richness across taxa and across taxonomic scale. We focused on Arthropoda, Annelida and Mollusca. Additionally, we estimated regional species richness using expert‐identified samples of three NEON sentinel taxa: Carabidae, Culicidae and Ixodida. To sample pitfall animals, we filtered storage ethanol and employed environmental DNA‐barcoding methodologies to amplify and sequence extracted DNA from the filtrate for two regions of a mitochondrial gene. We assigned taxonomic names to these sequences at 97% similarity to reference sequences and calculated local taxonomic richness at the levels of species, genus, family and order. We calculated local species richness for 12 common invertebrate taxa. We used generalized linear models to describe the relationships between taxonomic richness and spatial, climatic and abundance predictor variables. At four taxonomic scales, ranging from species to order, taxonomic richnessincreased significantly as a function of latitude. Of the twelve invertebrate taxa weexamined, seven mirrored this positive latitudinal gradient in species richness. At theregional scale, two of three NEON Sentinel Taxa showed positive latitudinal gradientsin species richness. Temperature, precipitation, abundance and sequence read numberplayed minor roles in explaining patterns of taxonomic richness. When considering these mostly temperate sites that span 46 degrees of latitude, we found no support for the expected negative latitudinal gradients across taxa and taxonomic scales. Instead, for many of these taxa and taxonomic scales, we observed significant, positive richness gradients with increasing latitude among ground‐dwelling invertebrate communities. Thus, one of the most ‘general' patterns in biogeography was not found for most invertebrate taxa across temperate latitudes.

Plants Play Stronger Effects on Soil Fungal than Bacterial Communities and Co-Occurrence Network Structures in a Subtropical Tree Diversity Experiment.

ABSTRACTIncreasing biodiversity loss profoundly affects community structure and ecosystem functioning. However, the differences in community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria in association with tree species richness gradients are poorly documented. Here, we examined soil fungal and bacterial communities in a Chinese subtropical tree species richness experiment (from 1 to 16 species) using amplicon sequencing targeting the internal transcribed spacer 2 and V4 hypervariable region of the rRNA genes, respectively. Tree species richness had no significant effect on the diversity of either fungi or bacteria. In addition to soil and spatial distance, tree species richness and composition had a significant effect on fungal community composition but not on bacterial community composition. In fungal rather than bacterial co-occurrence networks, the average degree, degree centralization, and clustering coefficient significantly decreased, but the modularity significantly increased with increasing tree species richness. Fungal co-occurrence network structure was influenced by tree species richness and community composition as well as the soil carbon: nitrogen ratio, but the bacterial co-occurrence network structure was affected by soil pH and spatial distance. This study demonstrates that the community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria differ in the subtropical forest.IMPORTANCE Increasing biodiversity loss profoundly affects community structure and ecosystem functioning. Therefore, revealing the mechanisms associated with community assembly and co-occurrence network structure of microbes along plant species diversity gradients is very important for understanding biodiversity maintenance and community stability in response to plant diversity loss. Here, we compared the differences in community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria in a subtropical tree diversity experiment. In addition to soil and spatial distance, plants are more strongly predictive of the community and co-occurrence network structure of fungi than those of bacteria. The study highlighted that plants play more important roles in shaping community assembly and interactions of fungi than of bacteria in the subtropical tree diversity experiment.

Winter conditions structure extratropical patterns of species richness of amphibians, birds and mammals globally

AbstractAimThe aim was to derive global indices of winter conditions and examine their relationships with species richness patterns outside of the tropics.LocationAll extratropical areas (>25° N and 25° S latitudes), excluding islands.Time period2000–2018.Major taxa studiedAmphibians, birds and mammals.MethodsWe mapped three global indices of winter conditions [number of days of frozen ground (length of frozen ground winter); snow cover variability; and lack of subnivium (below‐snow refuge)] from satellite data, then used generalized additive models to examine their relationships with species richness patterns derived from range data.ResultsLength of frozen ground winter was the strongest predictor of species richness, with a consistent cross‐taxonomic decline in species richness occurring beyond 3 months of winter. It also often outperformed other environmental predictors of species richness patterns commonly used in biodiversity studies, including climate variables, primary productivity and elevation. In areas with ≥3 months of winter conditions, all three winter indices explained much of the deviance in amphibian, mammal and resident bird species richness. Mammals exhibited a stronger relationship with snow cover variability and lack of subnivium than the other taxa. Species richness of fully migratory species of birds peaked at c. 5.5 months of winter, coinciding with low species richness of residents.Main conclusionsOur study demonstrates that winter structures latitudinal and elevational gradients of extratropical terrestrial species richness. In a rapidly warming world, tracking the seasonal dynamics of frozen ground and snow cover will be essential for predicting the consequences of climate change on species, communities and ecosystems. The indices of winter conditions we developed from satellite imagery provide an effective means of monitoring these dynamics into the future.