Cryptic species lacking distinct morphological features are widespread among soil fauna, including such functionally significant groups as springtails, mites and enchytraeids. Their presence, diversity and biomass may impact ecosystem services provided by belowground ecosystems. However, traditionally, the potential effects of cryptic diversity in explaining the functional significance of different mesofauna species have been overlooked due to the widespread practice of morphology‐based species identification. This review synthesizes the current state of knowledge on soil fauna cryptic species identification, emphasizing specific molecular techniques as the most reliable and precise method currently available for detecting and unravelling cryptic diversity. We analysed 326 scientific contributions available via Scopus or Web of Science, compiling information on genetic markers used to study cryptic diversity, including targeted gene regions, PCR primers and methods for estimating genetic distances. For comprehensive genetic analysis, combinations of mitochondrial Cytochrome c Oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) genes, together with nuclear markers such as 28S ribosomal RNA (28S rRNA) or Histone H3 (H3), are most commonly used. Our analysis revealed taxon‐specific thresholds: while COI divergences greater than 3% typically indicate cryptic species in collembolans, higher thresholds appear justified for mites (up to 17%) and enchytraeids (up to 5%) when supported by conserved nuclear markers (28S/H3), ecological or geographic coherence and the absence of intermediate forms. Advances in molecular research have also facilitated the analysis of cryptic diversity within morphospecies an—approach widely applied in soil ecology, especially when species‐level identification is hindered by limited taxonomic literature or expertise. However, our findings also demonstrated that it is a long way before methodological development in molecular approaches would ensure reliable cryptic species identifications in soil mesofauna. Even more should be done in linking the revealed cryptic diversity with its functional implications and possible differences in responding to environmental change. Besides these current limitations, we are positive that deeper integration of cryptic diversity knowledge into soil ecological research will significantly increase the reliability and precision of soil functions and services assessment.

Soil fauna perform a plethora of vital ecological functions and are often used as indicators of ecosystem disturbances. Investigating their taxa, functional diversity, and abundance is essential to assess ecosystem resilience, detect environmental stress, and guide conservation efforts. In this study, we investigated the taxonomic richness, diversity, and total and functional group abundance of soil macrofauna, as well as the environmental parameters of five model forests with different types of forest management (referred to as the “forest type”) within a temperate region of European Russia. These model forest types were subject to various types of forest management and were located in and around the Central Forest State Nature Biosphere Reserve (Tver Oblast, Russia): zonal forest (hereinafter referred to as the “zonal forest” treatment), forest disturbed by recreation (“recreational forest”), spruce forest monoculture (“monoculture”), secondary birch forest (“secondary forest”), and clear-cut site (“clear-cut”). We found that there was a significant difference in the total and average taxonomic richness of the macrofauna between the studied model forests, but no difference in mean abundance. The greatest difference was observed between the recreational (26 taxa, 11.2 ± 1.3 per site), monocultural (12 taxa, 4.8 ± 1.9 per site), and zonal (13 taxa, 4.5 ± 1.3 per site) forest types, while the macrofauna taxonomic composition was similar between the monocultural and control forests and significantly differed from that in the recreational and secondary forests and clear-cuts. Mobile taxa, mainly predators, were prevalent in the clear-cuts, while saprophages and phytophages dominated in the zonal forests and monocultures. The most important environmental factors influencing the macrofauna communities were the depth, mass, and composition of the litter, which depended on the presence of spruce (Picea abies), but not on soil parameters, the projective vegetation cover, or the abundance of microorganisms. Our study showed that anthropogenic disturbance in natural forests may not significantly alter the total abundance of the macrofauna, but it can impact the taxonomic composition and diversity of soil invertebrates. Therefore, greater attention should be given to analyzing functional and taxonomic diversity rather than relying solely on abundance data. Our findings highlight the importance of studying both the roles and diversity of soil species, not just their abundance, to better understand and protect natural ecosystems in the face of human impact.

The study of Palaearctic enchytraeid taxonomic richness revealed the limitations of applying morphological identification methods to certain species of the genus Cognettia. The use of molecular approaches enabled the identification of individuals belonging to C. chlorophila among immature and fragmented enchytraeids that had initially been identified morphologically as C. sphagnetorum s.l. These findings substantially extend the known distribution range of C. chlorophila eastward. Reliable distribution data for C. chlorophila and C. sphagnetorum s.s., obtained through genetic analysis, complement existing evidence of their coexistence in shared habitats and highlight questions concerning their biotopic preferences. It is hypothesized that the relatively low level of genetic diversity in these species is associated with potential postglacial dispersal routes of C. sphagnetorum s.l. from Scandinavian refugia and with species-specific biological characteristics.