Effects of amphipod size, species and their syntopic occurrence on isotopic metrics of trophic position within the linear mixed-effects models of a, b referenced δ13C (ΔC) and c, d of trophic level (TL) by a, c non-syntopic vs. b, d syntopic sites. See Table 2 for effect tests. Grey asterisks between species’ lines indicate significant (p < 0.05) interspecific differences at corresponding size extremes according to post hoc analysis. Not shown here, but this analysis also indicated significant ΔC differences within the smallest and largest specimens of G. roeselii occurring in non-syntopic vs. syntopic sites.