Urbanization affects the taxonomic and functional alpha and beta diversity of fish assemblages in streams of subtropical China

Abstract

Understanding human-induced changes in biodiversity and the environment can provide important references for managing and conservating freshwater fish. To date, most studies on the influence of urbanization on fish assemblage diversity have focused on large rivers, estuaries, and urban ponds; the process and mechanism of urbanization driving diversity changes in fish assemblages in headwater streams are unclear. We assessed the effects of urbanization on the taxonomic and functional alpha and beta diversity of fish assemblages in the headwater streams of the Xin’an River in China. Our results showed that compared with natural segments, urban segments had higher species richness and lower functional richness, which resulted from the gain of native invasive species and the loss of endemic species; fish assemblages also became taxonomically differentiated but functionally homogenized. In addition, ΔFD (difference value in functional beta diversity between urban and natural segments) was significantly positively correlated with ΔTD (difference value in taxonomic beta diversity between urban and natural segments), whereas only ΔFD was significantly negatively related to the urbanization indicators (e.g. urban land use and ammonia nitrogen concentration). Thus, a combination of taxonomic and functional diversity indices better reveals how fish biodiversity responds to urbanization. Our study provides evidence of urbanization-induced changes in fish assemblages as well as early warning signs for urban-disturbed ecosystems, both of which will benefit fish conservation in headwater streams.