Rapid urbanization reduces genetic diversity and increases genetic differentiation of a lynx spider Oxyopes sertatus in central Taiwan

Urbanization is a dominant force driving destructive and irreversible changes of natural habitats in modern times. While the effects of urbanization on community composition and phenotypic responses are well-documented, its influence on genetic diversity and population structure remains understudied, particularly for invertebrates in subtropical regions. This study tested the hypothesis that urbanization reduces genetic diversity and increases population differentiation in the lynx spider Oxyopes sertatus, a common foliage-dwelling spider in Taiwan. We sampled 245 individuals from 17 sites distributed along an urban-rural gradient and quantified urbanization intensity using land-use composition at both landscape (4 km²) and local (0.25 km²) scales. Genetic diversity and population differentiation were assessed using mitochondrial cytochrome oxidase I (COI) and genome-wide single nucleotide polymorphism (SNP) generated via restriction site-associated DNA sequencing (RAD-seq). The results showed that genetic diversity declined with increasing urbanization intensity, with the strongest effects detected in genome-wide diversity indices. Urban populations also showed greater genetic differentiation compared to rural populations, indicating urban environments impose physical barriers to gene flow and elevate differentiation. However, STRUCTURE and principal component analysis (PCA) revealed no distinct genetic clusters, suggesting that dispersal may still occur. Our findings suggest that even a widespread and abundant spider species can undergo rapid genetic diversity loss in urban landscapes. These results highlight the importance of incorporating habitat connectivity into urban planning to maintain wildlife gene exchanges and support biodiversity in rapidly urbanizing regions.