The diversity of juvenile salmonids does not affect their competitive impact on a native galaxiid
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We used an invaded stream fish community in southern Chile to experimentally test whether the diversity of exotic species affects their competitive impact on a native species. In artificial enclosures an established invasive, rainbow trout, Oncorhynchus mykiss, and a potential invader, Atlantic salmon, Salmo salar, reduced the growth rate of native peladilla, Aplochiton zebra, by the same amount. In enclosures with both exotic salmonids, the growth rates of all three species were the same as in single exotic treatments. While neither species identity nor diversity appeared to affect competitive interactions in this experiment, the impact of salmonid diversity may vary with the type of interspecific interaction and/or the species identity of the exotics. Our experiment links two prominent concepts in invasion biology by testing whether the result of invasional meltdown, an increase in the diversity of exotic species, affects their impact through interspecific competition, the mechanism invoked by the biotic resistance hypothesis.
KeywordsExotic species diversity Interspecific competition Salmonids Galaxiids Stream enclosure experiment Aquaculture
We thank Abraham Guevara for allowing us to conduct this experiment on his land and the neighbors of Guardanamo for their assistance and understanding. We thank Sonia Consuegra, Jason Dunham and Ian Fleming for discussions and comments. This work was funded by the Department for Environment Food and Rural Affairs (DEFRA, UK) Darwin Initiative Grant # 162-15-020 with support from the Universidad de Los Lagos.
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