Trophic niche divergence at the local scale
To identify trophic niche competition, niche overlaps were analyzed between all species pairs of the 7 species in the 5 sampling sites respectively. The 7 species may not be present at all the 5 sites. It was found that, some species pairs showed some extent overlaps in their trophic niches, some not. Interestingly, all sister species pairs except one showed no overlap, and the overlaps between sister species were significantly less than those between closely related species (excluding sister species) (P =0.008 < 0.05), indicating the possible competitive exclusion there (Table. 1, Supplement Fig. A1).