Altitudinal patterns of soil nematode community diversity and functional structure in the Boysun Mountains, Uzbekistan

Mountain ecosystems provide natural gradients for investigating biodiversity responses to environmental variation. This study examined the effects of altitude on the taxonomic diversity, trophic structure, and functional composition of soil nematode communities in the Boysun Mountains, southern Uzbekistan. Soil and rhizosphere samples associated with perennial plant communities were collected from four altitudinal zones (<800, 800-1500, 1500-2000, and >2000 m a.s.l.), yielding a total of 128 samples. Nematodes were extracted using modified Baermann, flotation, and decantation techniques and identified to species level using morphological and morphometric characteristics. A total of 102 nematode species belonging to two classes, seven orders, and numerous trophic and colonizer-persister (c-p) groups were recorded. Tylenchida, Rhabditida, and Dorylaimida were the dominant orders. Bacterivores represented the most diverse trophic group (35.2% of all species), followed by ectoparasitic plant feeders (22.5%). The c–p structure was dominated by CP-2 (42.1%) and CP-3 (30.4%) taxa. Nematode community composition varied markedly along the altitudinal gradient, with high-elevation communities characterized by a greater proportion of plant-parasitic and persister taxa, whereas lower elevations were increasingly dominated by bacterivorous colonizers. Diversity indices revealed a unimodal pattern, with maximum Shannon, Simpson, and richness values occurring at intermediate elevations (800-2000 m). Jaccard similarity analysis indicated strong species turnover along the gradient, with communities above 2000 m forming a distinct assemblage. These findings demonstrate that altitude is a major driver of soil nematode diversity and functional organization in the Boysun Mountains and highlight the value of nematodes as sensitive indicators of soil ecosystem condition, food-web structure, and ecological stability in mountain environments.