Fig 1.
Sampling locations around Lake Biwa.
Red triangles indicate lake sites (L1–L9) and blue circles indicate river sites (R1–R9). Samples captured in the sites with filled symbols were used for both morphological and molecular analyses, and those with open symbols were only for molecular analysis. These sampling sites are generally categorized as rocky zone (violet shadow), pebbly zone (orange shadow), and sandy zone (no shadow) based on the bottom environments.
Table 1.
Locality name, geographic coordinate, sampling year, and sample size for specimens used in this study.
Fig 2.
Measurement parts of morphological traits for Pseudogobio esocinus.
Standard length (SL), body depth (BD), body width (BW), caudal peduncle depth (CPD), head length (HL), snout length (SnL), mouth length (ML), and mouth width (MW).
Fig 3.
Scatter plots and histograms of PC2 and PC3.
Contribution ratio of each principal component in the variation excluding PC1’s contribution is shown in parentheses. Specimens of Pseudogobio esocinus were collected from Lake Biwa and the surrounding rivers (red, lake sites; blue, river sites). Distributions of PC2 and PC3 scores showed unimodality both in lake samples (Silverman’s tests, PC2, p = 0.57; PC3, p = 0.74) and river samples (PC2, p = 0.71; PC3, p = 0.77). The bottom panels are scatter plots of PC2 and PC3 for each local sample in the lake (left) and rivers (right). Photos are the ventral views of representative specimens with wide and narrow mouths of the specimens collected from Lake Biwa (narrow, L4; wide, L3) and rivers (narrow, R1; wide, R6).
Fig 4.
Lateral views of head of the representative specimens in Pseudogobio esocinus collected from Lake Biwa.
Left, wide mouth; right, narrow mouth. (A) Double-staining specimens, (B) schematic bony structure and associated ligaments (pale brown lines) with showing kinematics of upper jaw protrusion. The retracted (a, c, e, g) and protruded states (b, d, f, h) of the mouths are shown. The kinethmoid (kin), a median sesamoid bone, connects the upper jaw bones with the neurocranium mediated by the ligaments and rostral cartilage (rc). The kinethmoid leans a little to the neurocranium when the jaws are closed, whereas it rotates rostrally during jaw protrusion. Blue arrows indicate different extents of rotation of the kinethmoid causing different degrees of upper jaw protrusion between wide and narrow mouth specimens. max, maxilla; pmx, premaxilla; nc, neurocranium; pal, palatine.
Fig 5.
Diet compositions of Pseudogobio esocinus in lake sites (L4, L6) and river sites (R1, R7).
The number of fish specimens used for diet analysis is shown in parentheses.
Fig 6.
Relationship between PC scores and the proportion of amphipods in diet of Pseudogobio esocinus.
All the fish specimens were collected from L4 in Lake Biwa.
Fig 7.
Bayesian assignment analysis based on 14 microsatellite-locus data.
The samples of Pseudogobio esocinus were captured in Lake Biwa and the surrounding rivers. (A) ΔK as function of the number of assumed populations (K = 1–6). (B) Results of the assignment for K = 3. Each vertical bar indicates an individual partitioned into the three genetic clusters (cluster 1, red; cluster 2, green; cluster 3, blue). (C) The average q-value of cluster 1, which is the proportion of the genetic component in a location sample. Distinct letters indicate significant differences in that value in multiple comparison test under Bonferroni correction (significance level = 0.05).