Changes in taxonomic and functional diversity of an urban stream fish assemblage: A 30-year perspective

The study examines the impact of urbanization on freshwater fish diversity in an urban stream in East Texas over nearly three decades, comparing data from 1989-1990 to 2018-2019. While traditional approaches focus on taxonomic diversity, this study also incorporated functional diversity to better understand changes in fish communities. Although species and functional richness remained similar across the studied periods, species composition showed significant changes. Notably, the later assemblage (2018-2019) exhibited higher functional dispersion and evenness. Some species were locally extirpated, whereas others, including invasive and native tolerant species, colonized the system, possibly due to increased human activities in this urbanized area. Unlike the typical decline in diversity associated with urbanization, this scenario saw a shift in species composition and an increase in functional diversity, reflecting the complexity of urbanization effects on aquatic ecosystems. The findings underscore the necessity for more comparative and sentinel species-targeted studies to better evaluate and conserve freshwater ecosystems amidst urbanization.