Environmental Heterogeneity and Ptyctimous Mite Diversity in Protected Areas of North-Western Poland

Legal forms of nature conservation rarely take invertebrates into account, including soil fauna, and therefore they are of limited effectiveness for this group of organisms. The aim of this study was to assess how natural heterogeneity of nature reserves influences preservation of the biodiversity of soil invertebrates. The research was conducted in the period 2024–2025 in ten habitat-diverse nature reserves located in north-western Poland. The model group used in this study were ptyctimous mites (Acari: Oribatida), which are among the best-studied free-living mites in Poland. In 176 samples collected from 20 types of habitats, 21 species were identified, representing 50% of all ptyctimous mites known from Poland. The number of species recorded in each reserve ranged from 12 in Przełom rzeki Dębnicy reserve to 16 in Dęby Wilczkowskie reserve. The highest Shannon–Weaver diversity index, has been recorded for Nad Jeziorem Liptowskim reserve. None of the species recorded in the examined sites was very frequent or highly abundant, which indicates a balanced community structure and absence of major disturbances in the soil environment of the examined reserves. The species occurring in all ten reserves and in the majority of habitats were common in the whole area of Poland: Euphthiracarus cribrarius (Berlese, 1904), Phthiracarus laevigatus (C. L. Koch, 1841), Phthiracarus longulus (C. L. Koch, 1841), and Phthiracarus nitens (Nicolet, 1855). In contrast, Mesotritia nuda (Berlese, 1887) and Microtritia minima (Berlese, 1904) were the two stenotopic species. The species diversity of communities in the examined reserves was determined mostly by the habitat diversity within the reserves and by their history. The results indicate that in order to protect diverse communities of soil fauna it is crucial to protect many small, yet habitat-diverse, areas.