Taxonomic diversity and abundance of enchytraeids (Annelida, Clitellata, Enchytraeida) in the Northern Palaearctic. 1. Asian part.

Background: Enchytraeids, or potworms, are tiny oligochaetes that are distributed worldwide in many terrestrial, freshwater and marine ecosystems. Despite their key role in the functioning of ecosystems, the diversity and abundance of Enchytraeidae are rarely studied due to the laborious process of species identification. The present study addresses this gap and sheds some light on the distribution and abundance of enchytraeids in the lands of the Northern Palearctic. The provided dataset constitutes the latest and comprehensive field sampling of enchytraeid assemblages across the Asiatic part of the Northern Palearctic, encompassing an original set of soil samples systematically collected throughout the region from 2019 to 2022. New information: The dataset includes occurrences from 131 georeferenced sites, encompassing 39 species and 7,074 records. This represents the first dataset providing species-specific information about the distribution and abundance of terrestrial enchytraeids across an extensive geographic area covering the Asian sector of the Northern Palaearctic. The compiled dataset is the key for exploring and understanding local and regional enchytraeid diversity. It may also serve as a valuable resource for monitoring and conserving the entire soil biodiversity.

Enchytraeidae (Annelida: Oligochaeta) from Eastern Dagestan, Russia, with the description of a new species.

The first ever list of terrestrial enchytraeids of Eastern Dagestan includes 12 species belonging to five genera. Several species from studied localities may be assigned as undescribed, therefore additional comprehensive research of enchytraeid fauna from Eastern Dagestan is required. A new enchytraeid species of the genus Fridericia Michaelsen, 1889, Fridericia samurai sp. nov., is described from Eastern Dagestan, Russia. It clearly differs from other species of the genus by short and simple oesophageal appendages, not subdivided spermathecal diverticula, and the absence of spermathecal ectal glands and clitellum on ventral side.

Feeding habits and multifunctional classification of soil-associated consumers from protists to vertebrates.

Soil organisms drive major ecosystem functions by mineralising carbon and releasing nutrients during decomposition processes, which supports plant growth, aboveground biodiversity and, ultimately, human nutrition. Soil ecologists often operate with functional groups to infer the effects of individual taxa on ecosystem functions and services. Simultaneous assessment of the functional roles of multiple taxa is possible using food-web reconstructions, but our knowledge of the feeding habits of many taxa is insufficient and often based on limited evidence. Over the last two decades, molecular, biochemical and isotopic tools have improved our understanding of the feeding habits of various soil organisms, yet this knowledge is still to be synthesised into a common functional framework. Here, we provide a comprehensive review of the feeding habits of consumers in soil, including protists, micro-, meso- and macrofauna (invertebrates), and soil-associated vertebrates. We have integrated existing functional group classifications with findings gained with novel methods and compiled an overarching classification across taxa focusing on key universal traits such as food resource preferences, body masses, microhabitat specialisation, protection and hunting mechanisms. Our summary highlights various strands of evidence that many functional groups commonly used in soil ecology and food-web models are feeding on multiple types of food resources. In many cases, omnivory is observed down to the species level of taxonomic resolution, challenging realism of traditional soil food-web models based on distinct resource-based energy channels. Novel methods, such as stable isotope, fatty acid and DNA gut content analyses, have revealed previously hidden facets of trophic relationships of soil consumers, such as food assimilation, multichannel feeding across trophic levels, hidden trophic niche differentiation and the importance of alternative food/prey, as well as energy transfers across ecosystem compartments. Wider adoption of such tools and the development of open interoperable platforms that assemble morphological, ecological and trophic data as traits of soil taxa will enable the refinement and expansion of the multifunctional classification of consumers in soil. The compiled multifunctional classification of soil-associated consumers will serve as a reference for ecologists working with biodiversity changes and biodiversity-ecosystem functioning relationships, making soil food-web research more accessible and reproducible.

Size compartmentalization of energy channeling in terrestrial belowground food webs.

Size-structured food webs form integrated trophic systems where energy is channeled from small to large consumers. Empirical evidence suggests that size structure prevails in aquatic ecosystems, whereas in terrestrial food webs trophic position is largely independent of body size. Compartmentalization of energy channeling according to size classes of consumers was suggested as a mechanism that underpins functioning and stability of terrestrial food webs including those belowground, but their structure has not been empirically assessed across the whole size spectrum. Here we used stable isotope analysis and metabolic regressions to describe size structure and energy use in eight belowground communities with consumers spanning 12 orders of magnitude in living body mass, from protists to earthworms. We showed a negative correlation between trophic position and body mass in invertebrate communities and a remarkable nonlinearity in community metabolism and trophic positions across all size classes. Specifically, we found that the correlation between body mass and trophic level is positive in the small-sized (protists, nematodes, arthropods below 1 µg in body mass), neutral in the medium-sized (arthropods of 1 µg to 1 mg), and negative in the large-sized consumers (large arthropods, earthworms), suggesting that these groups form compartments with different trophic organization. Based on this pattern, we propose a concept of belowground food webs being composed of (1) size-structured micro-food web driving fast energy channeling and nutrient release, for example in microbial loop; (2) arthropod macro-food web with no clear correlation between body size and trophic level, hosting soil arthropod diversity and subsidizing aboveground predators; and (3) "trophic whales," sequestering energy in their large bodies and restricting its propagation to higher trophic levels in belowground food webs. The three size compartments are based on a similar set of basal resources, but contribute to different ecosystem-level functions and respond differently to variations in climate, soil characteristics and land use. We suggest that the widely used vision of resource-based energy channeling in belowground food webs can be complemented with size-based energy channeling, where ecosystem multifunctionality, biodiversity, and stability are supported by a balance across individual size compartments.