Abstract
The Kizil reservoir in the Tarim River basin is an important habitat for the native Schizothoracinae fish (including Aspiorhynchus laticeps, Schizothorax biddulphi, Schizothorax eurystomus, Schizothorax intermedius and Schizothorax barbatus). Unfortunately, these species are threatened by many exotic fish, such as Ctenopharyngodon idellus, Silurus asotus. As an isolated habitat, the Kizil reservoir is an ideal area for studying biological invasions. However, the impact of invasive species on indigenous species in this reservoir remains unknown. In this study, the niche width and niche overlap between invasive and indigenous species in Kizil reservoir were studied based on stable isotope analysis. The results showed that niche width of two invasive species, S. asotus and C. idellus, was larger than that of native fish species, which confirmed the hypotheses that successful invaders have larger niche width. The niche overlap analysis showed that the two invasive species had high niche overlap with native fish species, which meant that there might be intensive interspecific competitions between them. The invasion of non-native species could be the main reason for the decrease of native species in the Kizil reservoir.
Highlights
Invasive species have strong impacts on ecosystem integrity and biodiversity
Using stable isotope analysis (SIA) and subsequent comparisons of species isotopic niche widths and their degree of overlap, our study aimed to prove that some invasive fish are likely to be directly competing with native fauna for dietary resources in the Kizil reservoir, and provide reference for specific measures to protect native biodiversity, providing support for the ecological conservation of the Kizil reservoir
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Summary
Invasive species have strong impacts on ecosystem integrity and biodiversity. Freshwater ecosystems, especially rivers, which can be effectively considered biogeographic islands, are susceptible to the establishment of invasive species because their ecological space is often ‘unsaturated’ with native species and is more likely to favor the establishment of non-natives [1,2]. Ecological effects of invaders may include behavioral shifts in native species, alteration of native habitat, alteration of food webs and trophic dependencies, and extirpation of native biota [3,4]. Quantifying the impacts of invasive species can be challenging due to the complexity of ecological interactions [12], in aquatic ecosystems. Isotopic ratios are conserved up through the food web, with predictable isotopic shifts (or fractionation) at every trophic
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