Taxonomic structure of oribatida mite (Acari: Oribatida) populations in tree-related microhabitats of the Ukrainian Carpathians

Ecosystem engineers, or foundational species, are organisms that significantly alter habitats by physically modifying abiotic or biotic conditions for other species. These modifications often lead to an increase in habitat heterogeneity, which typically results in higher levels of local biodiversity [20]. A prominent example of such species is trees, particularly within primeval forest ecosystems. These environments host a variety of tree-related microhabitats – unique substrates and structures that provide living conditions for numerous species of plants, animals, and fungi [13]. Arthropods represent the most diverse component of terrestrial ecosystems, with many taxa specifically associated with tree microhabitats [15]. Their abundance and specialization contribute significantly to the complexity of forest ecosystems. This study is the first in Ukraine to describe the taxonomic structure of oribatid mites across various types of tree microhabitats. The research is based on material collected in 2024 from root buttress cavities, bark fissures and trunk holes, dendrotelms (tree water pools), trunk microsoil, and broken tree trunks. The results reveal a high degree of habitat specificity among armored mites. A total of 21 families were identified, representing approximately one-third of all oribatid families known in the Ukrainian Carpathians. The most abundant family was Oppiidae, comprising over one-quarter of all mites recorded in the studied microhabitats. Moreover, different microhabitats showed marked differences in mite population structure: the highest species diversity was found in trunk microsoil, whereas the highest individual density was observed in bark fissures.