3.2 Diets
Resource segregation was clear in the two morphs of S. thermalis . The planktivorous and benthivorous morphs showed low dietary overlap (Cxy = 0.42). By wet weight, zooplankton composed a larger portion (43.9%) (Figure 7) of the gut contents in the planktivorous morph than in the benthivorous morph. Most of the zooplankton belonged to Rotifera (37.67%) and Copepoda (5.99%), both of which also had a high occurrence rate (100%) but constituted a small portion (0.02%) of the gut contents of the benthivorous morph. Small fishes (34.98%) and hydrophilic insects (17.08%) composed the second largest portion of prey in the gut of the planktivorous morph, which contained a larger portion of these prey items than did the benthivorous morph (29.40% and 8.64%, respectively). However, the benthivorous morph ingested a larger proportion of periphytic algae (47.93%) and zoobenthos (12.78%), based on the gut contents, than did the planktivorous morph, and Bacillariophyta (43.66%) and Chironomida larvae (9.56%) constituted the largest portion of the periphytic algae and zoobenthos, respectively. The nonparametric Kruskal-Wallis test showed that the morphs differed significantly in the wet percentage of food composition of periphytic algae (χ2: 40.30, p < 0.001), zooplankton (χ2: 46.28, p < 0.001), zoobenthos (χ2: 43.34, p < 0.001), hydrophilic insects (χ2: 25.58, p <0.001), small fishes (χ2: 15.91, p <0.001) and others (χ2: 5.29, p < 0.05). The detailed dietary data are shown in Table S3.