Predicting the ecological impacts of an alien invader: Experimental approaches reveal the trophic consequences of competition

J. Robert Britton*, C Gutmann Roberts, Trigo F Amat, Emma T. Nolan, Santis V De

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

<jats:title>Abstract</jats:title><jats:p> <jats:list> <jats:list-item><jats:p>Ecological theory on the trophic impacts of invasive fauna on native competitors is equivocal. Whilst increased interspecific competition can result in coexisting species having constricted and diverged trophic niches, the competing species might instead increase their niche sizes to maintain energy intakes. Empirical experiments can test invasion theory on competitive interactions and niche sizes across different spatial scales and complexity.</jats:p></jats:list-item> <jats:list-item><jats:p>The consequences of increased interspecific competition from a model alien fish <jats:italic>Leuciscus idus</jats:italic> were tested on two taxonomically and trophically similar native fishes, <jats:italic>Squalius cephalus</jats:italic> and <jats:italic>Barbus barbus</jats:italic>. Competitive interactions were tested in tank aquaria using comparative functional responses (<jats:styled-content style="fixed-case">CFR</jats:styled-content>s) and cohabitation trials. The consequences of these competitive interactions for the trophic niche sizes and positions of the fishes were tested in pond mesocosms.</jats:p></jats:list-item> <jats:list-item><jats:p>Comparative functional responses revealed that compared to <jats:italic>B. barbus, L. idus</jats:italic> had significantly higher attack and consumption rates; cohabitation trials revealed <jats:italic>B. barbus</jats:italic> growth rates were depressed in sympatry with <jats:italic>L. idus</jats:italic>. For <jats:italic>L. idus</jats:italic> and <jats:italic>S. cephalus,</jats:italic> differences in their functional response parameters and growth rates were not significant.</jats:p></jats:list-item> <jats:list-item><jats:p>Pond mesocosms used stable isotope metrics to quantify shifts in the trophic niche sizes of the fishes between allopatry and sympatry using a substitutive experimental design. Isotopic niches were smaller and more divergent in sympatric paired species than predicted by their allopatric treatments, suggesting trophic impacts from interspecific competition. However, an all‐species sympatric treatment revealed similar niche sizes with allopatry. This maintenance of niche sizes in the presence of all species potentially resulted from the buffering of direct competitive effects of the species pairs by indirect effects.</jats:p></jats:list-item> <jats:list-item><jats:p>Experimental predictions from tank aquaria assisted the interpretation of the constricted and diverged trophic niches detected in the paired‐species sympatric treatments of the pond mesocosms. However, the all‐species sympatric treatment of this experiment revealed greater complexity in the outcomes of the competitive interactions within and between the species. These results have important implications for understanding how alien species integrate into food webs and influence the trophic relationships between native species.</jats:p></jats:list-item> </jats:list> </jats:p>
Original languageEnglish
Pages (from-to)1066-1078
Number of pages0
JournalJournal of Animal Ecology
Volume88
Issue number7
Early online date10 May 2019
DOIs
Publication statusPublished - Jul 2019

Fingerprint

Dive into the research topics of 'Predicting the ecological impacts of an alien invader: Experimental approaches reveal the trophic consequences of competition'. Together they form a unique fingerprint.

Cite this