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.