Communities of epigeic spiders (Arachnida, Araneae) in forest ecosystems of the northeastern slope of Mt. Pikui (Ukrainian Carpathians)

A study was conducted on the assemblages of epigeic spiders in forest ecosystems on the northeastern slope of Mt. Pikui(Vododilno-Verkhovyna Range). The surveyed habitats are: (1) an old-growth sycamore–beech forest at 890–900 m a.s.l., (2) an old-growth sycamore–beech forest in proximity of secondary subalpine meadow (1090–1100 m a.s.l.), and (3) a beech–rowan sparse woodland at the upper forest limit adjoining secondary subalpine meadows (1126 m a.s.l.).A total of 38 spider species belonging to 10 families were identified. The majority of species belonged to Linyphiidae (26 species; 68.4 %) and Agelenidae (3 species; 7.9 %), while the remaining eight families were represented by one or two species each. The species richness was highest in the beech–rowan sparse woodland (25 species), followed by the upper-elevation old-growth forest (18 species) and the lower-elevation old-growth forest (16 species). The core of the dominant assemblage comprised eight species: Cybaeus angustiarum, Tenuiphantes tenebricola, Coelotes pickardi carpathensis, Callobius claustrarius, Diplocephalus picinus, Inermocoelotes inermis, Palliduphantes milleri, and Microneta viaria. These eight species together accounted for 95.5 % of all individuals. The most pronounced differences in species composition among habitats were driven by subrecedent species, whose presence was specific to each ecosystem. Taxonomic diversity and evenness indices showed a declining trend along the elevational gradient: beech–rowan sparse woodland ‒ upper-elevation old-growth forest ‒ lower-elevation old-growth forest. According to ANOVA followed by Tukey’s HSD post hoc test, the differences in diversity index values among the three forest ecosystems were statistically significant (p < 0.05). Non-metric multidimensional scaling (NMDS) based on Bray–Curtis dissimilarity revealed closer affinities between the assemblages of the sparse woodland and the upper old-growth forest, while the assemblage of the lower-elevation old-growth forest formed a distinctly separate group.