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

Study Extent

The study sites were situated in undisturbed zonal ecosystems across the seven types of biomes studied, as classified by WWF (Olson et al., 2001): tundra, boreal forests, temperate coniferous forests, temperate broadleaf and mixed forests, temperate grasslands, savannas and shrublands, flooded grasslands and savannas, and desert and xeric shrublands. In each of the biomes, we collected a varying number of sites due to differences in sampling effort and logistical availability. Specifically, in tundra, we examined 13 sites; in boreal forests – 59 sites; in temperate coniferous forests –5 sites; in temperate broadleaf and mixed forests – 11 sites; in temperate grasslands, savannas, and shrublands – 30 sites; in flooded grasslands and savannas – 5 sites; and in desert and xeric shrublands – 8 sites. We selected sampling sites in areas with minimal human disturbance. In arid regions, we opted for the most well-watered (yet non-flooded) locations.

Sampling

The sampling protocol followed to widely accepted methods in soil zoology and ecology (Ghilarov 1975, Coleman et al., 2004). Soil monoliths for studying enchytraeids were collected using a steel corer with a diameter of 5 cm, reaching a depth of 10 cm. At each site, a varying number of soil monoliths were sampled, ranging from 1 to 7. After sampling, soil monoliths were promptly sealed in plastic bags and transported to the laboratory at the A.N. Severtsov Institute of Ecology and Evolution using isothermal containers. Subsequently, the soil samples were stored in a refrigerator at 4°C until the extraction process. Enchytraeids were extracted from the soil using the wet funnel method as described by Didden et al. (1995). A sieve was positioned within each funnel, with a soil monolith placed in each sieve. Subsequently, tap water was poured into the funnel until the soil monolith was fully submerged. A test tube was affixed to every funnel, and these test tubes were then immersed in a container of room temperature water to prevent overheating of the extracted enchytraeids. The extraction process was conducted over a period of 16 to 24 hours. Following extraction, the tubes were separated from the funnels, and the contents of the tubes were emptied into petri dishes.

Quality Control

A total of 39 enchytraeid species were collected. Due to variations in the number of soil monoliths across different sites, the dataset expresses abundance as individuals per square meter. Enchytraeid species were identified in vivo immediately after the extraction procedure, following the guidelines of Schmelz and Collado (2010). For species not covered in this guide or described subsequently, original descriptions were used for comparison. Some of the species we have found exhibit distinct morphological differences from all known enchytraeid species. We are confident that these species have not yet been described in the literature. A comprehensive description of these species will be possible once more data has been collected. Therefore, we have decided to refer to them as Fridericia sp. 1, Enchytraeus sp. 1, Henlea sp. 1 and Henlea sp. 2 for now. Henlea sp. 1 and Henlea sp. 2 are large Henlea worms, both with unusually robust spermathecae. Fridericia sp. 1 is a medium-sized Fridericia species from mountainous Uzbekistan. Enchytraeus sp. 1 is possibly an obligate parthenogenetic species from the E. buchholzi group, characterized by underdeveloped male copulatory organs. The taxonomy of the identified enchytraeids has been standardized with the WoRMS database (Timm and Erséus, 2023). Scientific names were further validated using the GBIF species matching tool. Subsequently, the identified enchytraeids were utilized for additional molecular and isotopic analyses. Consequently, all instances of enchytraeid occurrences within the studied sites were documented as dwc:basisOfRecord = HumanObservation. Juvenile specimens were identified to the genus level. The identification of all enchytraeids was undertaken by Maxim Degtyarev.

Method steps

1. 1) The selection of study sites was driven by the intention to locate undisturbed areas displaying minimal or no signs of human activity. 2) Site sampling was carried out at a distance of no less than 100 meters from the borders of designated zonal sites within one of the seven biome types according to WWF (Olson et al., 2001): tundra, boreal forests, temperate coniferous forests, temperate broadleaf and mixed forests, temperate grasslands, savannas and shrublands, flooded grasslands and savannas, as well as desert and xeric shrublands. 3) At each site, soil monoliths were collected using a steel corer with a diameter of 5 cm, reaching a depth of 10 cm. 4) The transportation of soil monoliths was conducted in cooled isothermic containers to prevent soil overheating, which could lead to the mortality of organisms present. 5) Enchytraeids were extracted from the soil using the wet funnel method as described by Didden et al. (1995). 6) Following the extraction process, enchytraeids were identified in vivo to the species level using an Olympus BX-43 microscope. Subsequently, they were preserved in 96% alcohol for subsequent molecular and isotopic analyses.

Enchytraeids from terrestrial ecosystems in the Asiatic part of the Northern Palearctic.

1. Enchytraeida
   rank: order
2. Enchytraeidae
   rank: family
3. Animalia
   rank: kingdom
4. Annelida
   rank: phylum
5. Clitellata
   rank: class

This dataset presents the distribution and abundance of soil enchytraeids in the Asiatic part of the Northern Palaearctic.