Exotic Spartina alterniflora invasion changes temporal dynamics and composition of spider community in a salt marsh of Yangtze Estuary, China

Abstract

Spiders play important roles in regulating arthropod populations in terrestrial ecosystems. However, the impact of exotic plant invasion on the spider community is still poorly understood, especially in salt marsh systems, which are especially susceptible to this invasion. The exotic Spartina alterniflora has widely invaded the coastal wetlands of China, and this study aims to evaluate such effects on the spider diversity and community composition in the Jiuduansha wetland of Yangtze Estuary. To do this, for a one-year period, we have collected spiders from the marsh surface (SMS) as well as spiders from the plant foliage surface (SPFS) respectively in S. alterniflora-dominated marshes (SDM) and native Phragmites australis-dominated marshes (PDM) in Jiuduansha. Results showed S. alterniflora invasion generally had a positive effect on the biodiversities of both SMS and SPFS, but actually changed the seasonal fluctuation of species richness and abundance of SMS. According to principal component analysis, community compositions of SMS and SPFS were different between SDM and PDM. Specially, SMS community composition exhibited more obvious temporal patterns in PDM than in SDM. The Bray-Curtis dissimilarity index between SDM and PDM varied more between sampling months in SMS than in SPFS. Based on canonical correspondence analysis, tidal elevation significantly affected community compositions of SMS and SPFS in SDM. In contrast, for spiders in PDM, tidal elevation had a weakened effect on SMS community composition. This may be explained by the different distribution of the two plants at high and low tidal levels. In summary, our study suggests that S. alterniflora invasion has changed the temporal dynamic and composition of the spider community in the Jiuduansha wetland. In future research, it should be highlighted that variations in habitat characteristics and ecological niches of spiders are important in mediating the invasive effects of exotic plants on the native spider community.