Ground-dwelling spider assemblages as indicators of urbanization in Tisza River floodplain forest patches

Abstract We evaluated the impacts of urbanization on ground-dwelling spiders in isolated floodplain forest patches of the Tisza River system (Szeged, Hungary) along a rural-suburban-urban gradient. We investigated how human-mediated landscape acts as an ecological filter shaping assemblage-level functional traits, including habitat affinity, microclimatic preferences, and hunting strategies. Generalized linear modeling revealed that overall species richness and the richness of forest specialists remained statistically uniform across the urban-rural continuum. However, intensive urban forest management (canopy thinning and leaf litter removal) induced marked shifts in assemblage composition driven by microclimatic desiccation. While moisture-dependent, disturbance-sensitive forest taxa were suppressed in the urban forest patches, the opening of the habitat’ vegetation facilitated the establishment of dry-adapted (xerophilous), light-associated (photophilous), and open-habitat spiders. Indicator species analysis (IndVal) corroborated this structural turnover: Piratula hygrophila and Liocranoeca striata characterized undisturbed rural and suburban habitats, whereas Tenuiphantes tenuis , Drassyllus pusillus , Pardosa agrestis , and Zelotes apricorum emerged as distinct urban specialists. Our findings demonstrate that urbanization triggers a functional substitution of specialized riverine fauna with ubiquitous generalists. To preserve the unique biodiversity and ecological integrity of these vulnerable riparian remnants, local forest management intensity should be moderated, prioritizing the retention of dense canopy cover, and natural forest floor structure.