The ecological niche of aquatic invasive species from carbon and nitrogen stable isotope analysis
As species face increasing challenges from climate change and anthropogenic stressors, knowledge of traits that influence the survival of species across different geographic scales is paramount. The varying spread and distribution of aquatic invasive species (AIS) provides a model for determining key traits to long-term survival. Ecological niche is often used to investigate the success of invasive species, and a broad niche can provide scope for plasticity across different environments. As such, more widely established AIS were hypothesized to demonstrate a broader and more plastic ecological niche. We compared the widespread Round Goby (Neogobius melanostomus), Spiny Waterflea (Bythotrephes longimanus), Eastern Oyster (Crassostrea gigas) and Golden Star Tunicate (Botryllus schlosseri) to the rarely established Tubenose Goby (Proterorhinus semilunaris), Fishhook Waterflea (Cercopagis pengoi), Pacific Oyster (Crassostrea virginica) and Violet Tunicate (Botryllus violaceus) across invaded ranges in North America (collected 2011-2013, 8 sites/species pair, n = 20-50/site). Bayesian ellipses of stable isotopes (δ13C and δ15N) were used as tracers of diet driven ecological niche breadth and plasticity. Mussels (Dreissena sp. and Mytilus sp.) were used to measure source driven baseline variability of stable isotopes across spatial and temporal gradients.
Overall, higher trophic level (δ15N) and greater variation in isotopic niche breadth (ellipses of δ13C and δ15N) were found in more widespread AIS. Greater niche plasticity was positively associated with morphological variation and length of time since establishment in goby fishes. High body condition was positively correlated with niche breadth for tunicates and oysters. The relationship between variability in isotopic niche and broad establishment of invertebrates and fishes demonstrates the importance of dietary niche plasticity on long-term survival of species across broad geographic ranges. With increasing globalization of the human race and unpredictability of climate change impacts, determining the spread and distribution of species presents an increasing challenge. Our findings suggest that diet plasticity is associated with dispersal across a broad geographic distribution and can provide increased opportunity for plastic species under changing environmental conditions.