Do sympatric transgenic and non-transgenic common carps partition the trophic niche? A whole-lake manipulation study

Abstract

Genetically modified organisms (GMO) are a potential driver of human-induced global change and interactions occurring among GMOs and non-GMOs have important implications for ecosystem structure and functioning. Genetically modified fish (transgenic fish) can improve the production and characteristics of conventional fish strains currently exploited in aquaculture, but their ecological impacts on local food web remain less studied. We settled “all-fish” growth hormone gene-transgenic and non-transgenic common carp (carpT and carpNT) sympatrically in an artificial lake, and used stable isotope analysis to test the hypothesis that carpT and carpNT alter their trophic niche to facilitate coexistence through local niche partitioning. A general paradigm for coexistence of carpNT and carpT in this study was that carpNT increased the use of low-quality food resources (such as submerged plants) to mitigate the competition for limited resources (i.e., zoobenthos) resulting from niche partitioning. This change resulted in an enlarged niche width of carpNT and increased the niche overlap with its sympatric competitor, that is, carpT, which led to an increase in the individual specialization within the population to enhance resource use efficiency. This study represents the first controlled empirical test of the trophic interactions between competitive coexisting transgenic and non-transgenic organisms at population and individual levels. Our results indicate that competitive niche partitioning operating between carpNT and carpT shifts through time, emphasizing the importance of changing interspecific interactions when considering the ecological risk of transgenic species release, and it can be inferred that it is difficult for the escaped carpT to achieve the form of an explosive and most successful population than the wild carp.