Gut content analyses
Gut content differed significantly between lake and streams (PERMANOVA:
Pseudo-F 5,278: 3.7748, P = 0.039), but further
differed significantly between locations nested within habitats
(PERMANOVA: Pseudo-F 5,278: 6.8904, P = 0.001).
The contribution of zooplankton was significantly higher in lake
locations (average 75.4 % ± 40.6 SD) compared to streams (29.8 % ±
42.4) (Mann-Whitney U: Z1 = -4.730, P <
0.001, Table 2, Figure 4). In contrast, the contribution of benthic
invertebrates was significantly higher in streams (average 51.9 % ±
46.3 SD) compared to lake locations (average 21.5 % ± 38.8 SD)
(Mann-Whitney U: Z1 = -5.601, P <
0.001, Table 2, Figure 4). Furthermore, the contribution of terrestrial
insects was significantly higher in stream locations (average 18.2 % ±
35.8 SD) compared to lake locations (3.1 % ± 16.6 SD) (Mann-Whitney U:
Z1 = -3.978, P < 0.001, Table 2, Figure
4). Pairwise comparisons of the three diet categories between the
locations reflected the overall differences between lake and streams
(Table 3). In addition, it showed variation in resource use between
locations of the same habitat: minnows caught at location L3 had
significantly lower proportions of zooplankton in their guts compared to
L2, and L1, respectively (Table 3a, Figure 4). At this location, minnows
were characterized by a higher contribution from benthic invertebrates,
which explains the non-significant differences between the proportion of
benthic invertebrates in L3 and S2, and S3, respectively (Table 3b,
Figure 4). Furthermore, the proportion of terrestrial insects was
significantly higher in location S3 compared to all other locations
(Table 3c, Figure 4).