Trophic divergence
Diet. Food spectra of sympatric ecomorphs of Labeobarbusspp. were rather diverse and composed of i) detritus, ii) invertebrates
(mainly insects: Ephemeroptera, Hemiptera, Trichoptera, Coleoptera,
Hymenoptera, and Diptera), iii) macrophytes (remnants of helophytic and
semi-aquatic plants, represented by seeds, leaves, stems, and flower
parts, sometimes coupled with filamentous algae), and occasionally iv)
fish (juvenile parts or scales). Feeding of sympatric ecomorphs in all
four rivers studied was divergent but at various degree as estimated by
index of relative importance (Fig. 3B).
Detritus was the main component among food items in both generalized
(63.8-92.1%) and thick-lipped ecomorphs (27.1–79.0%) (Fig. 3B).
Generally, the diet of the thick-lipped ecomorph was more insectivorous
compared to generalized ecomorph in all rivers studied (Figure 3B).
Invertebrates in the diet of both ecomorphs were represented by larvae
of Ephemeroptera and Trichoptera, larvae and imagoes of Diptera and
Coleoptera as well as imagoes of Hemiptera, and Hymenoptera.
Contributions of invertebrates for fish feeding might be underestimated
due to their quick digestion. This is why we also provide data on N and
C stable isotope composition (see below).
Detailed description of the diet
of each ecomorph in certain rivers see in Supplementary material S4.
Stable Isotope
Composition.Basic statistics for both
δ15N and δ13C values is given in
Supplementary Table S5. The thick-lipped ecomorph had higher
δ15N values that generalized one in all comparisons
with statistically significant difference in four of six paired
comparisons: Birbir, p < 0.05; Didessa, p < 0.01;
Gojeb, p < 0.01; and Sore, p < 0.05 (Fig. 4 and
Supplementary Fig. S6). When
significant, the difference in mean δ15N values
between sympatric generalized and thick-lipped ecomorphs varied from
1.9‰ (Didessa) to 0.9‰ (Sore). Significant differences in
δ13C values between sympatric pairs were found in the
Didessa, Gojeb, and Sore Rivers. In all these cases, the lipped ecomorph
had higher δ13C values (the difference varied from
1.6‰ to 1.2‰).