Global Spore Sampling Project: A global, standardized dataset of airborne fungal DNA.

Novel methods for sampling and characterizing biodiversity hold great promise for re-evaluating patterns of life across the planet. The sampling of airborne spores with a cyclone sampler, and the sequencing of their DNA, have been suggested as an efficient and well-calibrated tool for surveying fungal diversity across various environments. Here we present data originating from the Global Spore Sampling Project, comprising 2,768 samples collected during two years at 47 outdoor locations across the world. Each sample represents fungal DNA extracted from 24 m3 of air. We applied a conservative bioinformatics pipeline that filtered out sequences that did not show strong evidence of representing a fungal species. The pipeline yielded 27,954 species-level operational taxonomic units (OTUs). Each OTU is accompanied by a probabilistic taxonomic classification, validated through comparison with expert evaluations. To examine the potential of the data for ecological analyses, we partitioned the variation in species distributions into spatial and seasonal components, showing a strong effect of the annual mean temperature on community composition.

Earthworms (Clitellata, Megadrili) of the world: an updated checklist of valid species and families, with notes on their distribution.

In the current paper we present an updated checklist of all the megadrile earthworms (Crassiclitellata: Annelida) in the world, and notes on the distribution of families worldwide. Biogeographic responses to geological phenomena including plate tectonics, as well as to past and present climate and habitat distributions, are the main factors determining the present distribution of earthworm families. A total of ca. 5,738 species/subspecies (5,406 species and 332 unique subspecies; i.e., not counting the nomino-typical subspecies) belonging to 23 families (including one non-crassiclitellate family: Moniligastridae) are currently recognized worldwide, of which three families (Tritogeniidae and Kazimierzidae from Southern Africa and Arecoidae, a new family from Brazil described herein), 35 genera and close to 1200 new taxa (including subspecies) were described in the 21st century. Nonetheless, the large number of still undescribed species will likely increase this value to well over 8,000 species. Ten families are monospecific and/or monogeneric and have a mostly restricted distribution. On the other hand, more than 87 widespread cosmopolitan species have been catalogued, some of them with important invasive potential, belonging mainly to families Lumbricidae, Acanthodrilidae, Benhamiidae, Megascolecidae, Rhinodrilidae and Ocnerodrilidae. Taxonomic housekeeping was performed for the preoccupied Rhinodrilidae genus Tairona Righi - herein substituted by Taironina nom. nov., and Guarani camaqua Rodríguez & Lima was reinstated and removed from synonymy with Criodrilus lacuum Hoffmeister, 1845, resulting in a wider definition of the Almidae family. Furthermore, Amynthas maximalis nom. nov. is proposed herein as a substitution name for the preoccupied name Amynthas maximus Qiu & Dong, 2019, and Arecoidae is proposed herein as a new monotypic family for the aquamegadrile species Areco reco Righi, Ayres & Bittencourt, 1978.

Integrating natural gradients, experiments, and statistical modeling in a distributed network experiment: An example from the WaRM Network.

A growing body of work examines the direct and indirect effects of climate change on ecosystems, typically by using manipulative experiments at a single site or performing meta-analyses across many independent experiments. However, results from single-site studies tend to have limited generality. Although meta-analytic approaches can help overcome this by exploring trends across sites, the inherent limitations in combining disparate datasets from independent approaches remain a major challenge. In this paper, we present a globally distributed experimental network that can be used to disentangle the direct and indirect effects of climate change. We discuss how natural gradients, experimental approaches, and statistical techniques can be combined to best inform predictions about responses to climate change, and we present a globally distributed experiment that utilizes natural environmental gradients to better understand long-term community and ecosystem responses to environmental change. The warming and (species) removal in mountains (WaRM) network employs experimental warming and plant species removals at high- and low-elevation sites in a factorial design to examine the combined and relative effects of climatic warming and the loss of dominant species on community structure and ecosystem function, both above- and belowground. The experimental design of the network allows for increasingly common statistical approaches to further elucidate the direct and indirect effects of warming. We argue that combining ecological observations and experiments along gradients is a powerful approach to make stronger predictions of how ecosystems will function in a warming world as species are lost, or gained, in local communities.

Global patterns in endemicity and vulnerability of soil fungi.

Fungi are highly diverse organisms, which provide multiple ecosystem services. However, compared with charismatic animals and plants, the distribution patterns and conservation needs of fungi have been little explored. Here, we examined endemicity patterns, global change vulnerability and conservation priority areas for functional groups of soil fungi based on six global surveys using a high-resolution, long-read metabarcoding approach. We found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan, West-Central Africa, Sri Lanka, and New Caledonia, with a negligible island effect compared with plants and animals. We also found that fungi are predominantly vulnerable to drought, heat and land-cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests, and woodlands. We stress that more attention should be focused on the conservation of fungi, especially root symbiotic arbuscular mycorrhizal and ectomycorrhizal fungi in tropical regions as well as unicellular early-diverging groups and macrofungi in general. Given the low overlap between the endemicity of fungi and macroorganisms, but high conservation needs in both groups, detailed analyses on distribution and conservation requirements are warranted for other microorganisms and soil organisms.

The importance of scavenging in ant invasions.

Recent work underscores that ants are highly proficient and ubiquitous scavengers. These tendencies extend to numerically and behaviorally dominant introduced ants, which exhibit a suite of traits that allow them to exploit and monopolize carrion to a greater extent than is widely appreciated. We thus contend that an understanding of how introduced ants fit into food webs remains incomplete. Monopolization of carrion resources by introduced ants could increase worker production, enhance the ability of these species to compete with and prey upon other organisms, and alter the strength of direct and indirect interactions within food webs. Future work should consider how ant invasions influence energy transfer within and between green and brown food webs.

Blind spots in global soil biodiversity and ecosystem function research.

Soils harbor a substantial fraction of the world's biodiversity, contributing to many crucial ecosystem functions. It is thus essential to identify general macroecological patterns related to the distribution and functioning of soil organisms to support their conservation and consideration by governance. These macroecological analyses need to represent the diversity of environmental conditions that can be found worldwide. Here we identify and characterize existing environmental gaps in soil taxa and ecosystem functioning data across soil macroecological studies and 17,186 sampling sites across the globe. These data gaps include important spatial, environmental, taxonomic, and functional gaps, and an almost complete absence of temporally explicit data. We also identify the limitations of soil macroecological studies to explore general patterns in soil biodiversity-ecosystem functioning relationships, with only 0.3% of all sampling sites having both information about biodiversity and function, although with different taxonomic groups and functions at each site. Based on this information, we provide clear priorities to support and expand soil macroecological research.

Towards an integrative understanding of soil biodiversity.

Soil is one of the most biodiverse terrestrial habitats. Yet, we lack an integrative conceptual framework for understanding the patterns and mechanisms driving soil biodiversity. One of the underlying reasons for our poor understanding of soil biodiversity patterns relates to whether key biodiversity theories (historically developed for aboveground and aquatic organisms) are applicable to patterns of soil biodiversity. Here, we present a systematic literature review to investigate whether and how key biodiversity theories (species-energy relationship, theory of island biogeography, metacommunity theory, niche theory and neutral theory) can explain observed patterns of soil biodiversity. We then discuss two spatial compartments nested within soil at which biodiversity theories can be applied to acknowledge the scale-dependent nature of soil biodiversity.

Global mismatches in aboveground and belowground biodiversity.

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well-being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas.

Disparidades Mundiales entre la Biodiversidad Sobre y Bajo el Suelo Resumen Las actividades humanas están acelerando el cambio en la biodiversidad mundial y han tenido como resultado unos servicios ambientales severamente amenazados. Una gran proporción de la biodiversidad terrestre está albergada en el suelo, pero la biodiversidad de este ha sido omitida de varias evaluaciones mundiales de biodiversidad y de las acciones de conservación, además de que el entendimiento de los patrones mundiales de la biodiversidad del suelo permanece limitado; particularmente, la extensión del traslape entre los puntos fríos y calientes de biodiversidad sobre y bajo suelo no está clara. Examinamos los patrones mundiales de estos traslapes mapeando los índices de biodiversidad sobre el suelo (mamíferos, aves, anfibios y plantas vasculares) y bajo el suelo (bacterias, hongos y macrofauna) que creamos con datos previamente publicados de la riqueza de especies. Las áreas de disparidad entre la biodiversidad sobre y bajo el suelo cubrieron el 27% de la superficie terrestre del planeta. El bioma de los bosques templados de plantas frondosas y mixtas tuvo la proporción más alta de celdas de cuadrícula con una biodiversidad alta sobre el suelo, pero baja para en el subsuelo, mientras que los biomas boreales y de la tundra tuvieron una biodiversidad intermedia bajo el suelo, pero baja para el sobre suelo. Aunque se requieren más datos sobre la biodiversidad del suelo, tanto para cubrir los vacíos geográficos como para incluir a taxones adiciones, nuestros resultados sugieren que la protección a la biodiversidad sobre el suelo puede no reducir suficientemente las amenazas para la biodiversidad del suelo. Dada la importancia funcional de la biodiversidad del suelo y el papel de los suelos en el bienestar humano, se debería considerar a la biodiversidad del suelo mucho más en las agendas políticas y en las acciones de conservación, adaptando a las prácticas de manejo para que mantengan a la biodiversidad del suelo y la consideren cuando designen áreas protegidas.

Side-swiped: Ecological cascades emanating from earthworm invasion.

Non-native, invasive earthworms are altering soils throughout the world. Ecological cascades emanating from these changes stem from earthworm-caused changes in detritus processing occurring at a mid-point in the trophic pyramid, rather than the more familiar bottom-up or top-down cascades. They include fundamental changes (microcascades) in soil morphology, bulk density, nutrient leaching, and a shift to warmer, drier soil surfaces with loss of organic horizons. In North American temperate and boreal forests, microcascades cause effects of concern to society (macrocascades), including changes in CO2 sequestration, disturbance regimes, soil quality, water quality, forest productivity, plant communities, and wildlife habitat, and facilitation of other invasive species. Interactions among these changes create cascade complexes that interact with climate change and other environmental changes. The diversity of cascade effects, combined with the vast area invaded by earthworms, lead to regionally important changes in ecological functioning.

Changes in the genetic structure of an invasive earthworm species (Lumbricus terrestris, Lumbricidae) along an urban - rural gradient in North America.

European earthworms were introduced to North America by European settlers about 400 years ago. Human-mediated introductions significantly contributed to the spread of European species, which commonly are used as fishing bait and are often disposed deliberately in the wild. We investigated the genetic structure of Lumbricus terrestris in a 100 km range south of Calgary, Canada, an area that likely was devoid of this species two decades ago. Genetic relationships among populations, gene flow, and migration events among populations were investigated using seven microsatellite markers and the mitochondrial 16S rDNA gene. Earthworms were collected at different distances from the city and included fishing baits from three different bait distributors. The results suggest that field populations in Alberta established rather recently and that bait and field individuals in the study area have a common origin. Genetic variance within populations decreased outside of the urban area, and the most distant populations likely originated from a single introduction event. The results emphasise the utility of molecular tools to understand the spatial extent and connectivity of populations of exotic species, in particular soil-delling species, that invade native ecosystems and to obtain information on the origin of populations. Such information is crucial for developing management and prevention strategies to limit and control establishment of non-native earthworms in North America.

Higher predation risk for insect prey at low latitudes and elevations.

Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.

The unseen invaders: introduced earthworms as drivers of change in plant communities in North American forests (a meta-analysis).

Globally, biological invasions can have strong impacts on biodiversity as well as ecosystem functioning. While less conspicuous than introduced aboveground organisms, introduced belowground organisms may have similarly strong effects. Here, we synthesize for the first time the impacts of introduced earthworms on plant diversity and community composition in North American forests. We conducted a meta-analysis using a total of 645 observations to quantify mean effect sizes of associations between introduced earthworm communities and plant diversity, cover of plant functional groups, and cover of native and non-native plants. We found that plant diversity significantly declined with increasing richness of introduced earthworm ecological groups. While plant species richness or evenness did not change with earthworm invasion, our results indicate clear changes in plant community composition: cover of graminoids and non-native plant species significantly increased, and cover of native plant species (of all functional groups) tended to decrease, with increasing earthworm biomass. Overall, these findings support the hypothesis that introduced earthworms facilitate particular plant species adapted to the abiotic conditions of earthworm-invaded forests. Further, our study provides evidence that introduced earthworms are associated with declines in plant diversity in North American forests. Changing plant functional composition in these forests may have long-lasting effects on ecosystem functioning.

Root foraging influences plant growth responses to earthworm foraging.

Interactions among the foraging behaviours of co-occurring animal species can impact population and community dynamics; the consequences of interactions between plant and animal foraging behaviours have received less attention. In North American forests, invasions by European earthworms have led to substantial changes in plant community composition. Changes in leaf litter have been identified as a critical indirect mechanism driving earthworm impacts on plants. However, there has been limited examination of the direct effects of earthworm burrowing on plant growth. Here we show a novel second pathway exists, whereby earthworms (Lumbricus terrestris L.) impact plant root foraging. In a mini-rhizotron experiment, roots occurred more frequently in burrows and soil cracks than in the soil matrix. The roots of Achillea millefolium L. preferentially occupied earthworm burrows, where nutrient availability was presumably higher than in cracks due to earthworm excreta. In contrast, the roots of Campanula rotundifolia L. were less likely to occur in burrows. This shift in root behaviour was associated with a 30% decline in the overall biomass of C. rotundifolia when earthworms were present. Our results indicate earthworm impacts on plant foraging can occur indirectly via physical and chemical changes to the soil and directly via root consumption or abrasion and thus may be one factor influencing plant growth and community change following earthworm invasion. More generally, this work demonstrates the potential for interactions to occur between the foraging behaviours of plants and soil animals and emphasizes the importance of integrating behavioural understanding in foraging studies involving plants.

Effects of an ecosystem engineer on belowground movement of microarthropods.

Ecosystem engineers affect other species by changing physical environments. Such changes may influence movement of organisms, particularly belowground where soil permeability can restrict dispersal. We investigated whether earthworms, iconic ecosystem engineers, influence microarthropod movement. Our experiment tested whether movement is affected by tunnels (i.e., burrows), earthworm excreta (mucus, castings), or earthworms themselves. Earthworm burrows form tunnel networks that may facilitate movement. This effect may be enhanced by excreta, which could provide resources for microarthropods moving along the network. Earthworms may also promote movement via phoresy. Conversely, negative effects could occur if earthworms alter predator-prey relationships or change competitive interactions between microarthropods. We used microcosms consisting of a box connecting a "source" container in which microarthropods were present and a "destination" container filled with autoclaved soil. Treatments were set up within the boxes, which also contained autoclaved soil, as follows: 1) control with no burrows; 2) artificial burrows with no excreta; 3) abandoned burrows with excreta but no earthworms; and 4) earthworms (Lumbricus rubellus) present in burrows. Half of the replicates were sampled once after eight days, while the other half were sampled repeatedly to examine movement over time. Rather than performing classical pairwise comparisons to test our hypotheses, we used AIC(c) to assess support for three competing models (presence of tunnels, excreta, and earthworms). More individuals of Collembola, Mesostigmata, and all microarthropods together dispersed when tunnels were present. Models that included excreta and earthworms were less well supported. Total numbers of dispersing Oribatida and Prostigmata+Astigmata were not well explained by any models tested. Further research is needed to examine the impact of soil structure and ecosystem engineering on movement belowground, as the substantial increase in movement of some microarthropods when corridors were present suggests these factors can strongly affect colonization and community assembly.

Genetic structure of invasive earthworms Dendrobaena octaedra in the boreal forest of Alberta: insights into introduction mechanisms.

Population genetic studies can help to determine whether invasive species are established via single vs. multiple introduction events and also to distinguish among various colonization scenarios. We used this approach to investigate the introduction of Dendrobaena octaedra, a non-native earthworm species, to the boreal forest of northern Alberta. The spread of non-native earthworms in forested systems is not well understood, although bait abandonment and vehicular transport are believed to be important. Mitochondrial DNA sequencing revealed that multiple introductions of this species have occurred in northern Alberta, although individual populations may have been established by either single or multiple invaders introduced on one or more occasions. There was no relationship between genetic distances and either geographical distances or distances along road networks, suggesting that human-mediated jump dispersal is more common than diffusive spread via road networks or via active dispersal. As well, genetic diversity was significantly greater at boat launches than roads, indicating that multiple introductions may be more likely to occur at those locations. Focusing management efforts on areas where multiple introductions are likely to occur may help to reduce invasive species' potential for adaptive evolution and subsequent rapid spread.