Figure legends
Fig.1 Sites for the collection of samples from ten lochs in North Uist and eight lochs in South Uist, Scotland (A. Map of United Kingdom B. Loch position in North Uist C. Loch position in South Uist with road map).
Fig. 2 The first two PCs of body armour traits for anadromous sticklebacks collected from North (Ash, circle) and South (orange, triangle) Uist. Traits were plate count and residual values (from body length) of 1st dorsal spine length (X1st.DSL), 2nd dorsal spine length (X2nd.DSL), pelvic spine length (PSL), length of pelvis (LPS), height of pelvis (HPS). PC1 (35.2%) describes overall variation in armour, with positive loadings of all variables. PC2 (22.75%) mainly describes variation in plate count (positive loading), but also reflects negative loadings for LPS and PSL. Ellipses represent 95% confidence levels within each data set.
Fig. 3 Mean standard length (± S.E.) of anadromous and resident fish shows little overall variation in size between North (Ash, circle) and South Uist (orange, triangle) sticklebacks. Resident stickleback of North and South Uist were significantly smaller than the anadromous fish.
Fig. 4 A. The first two principal components (PCs) of six body armour traits and standard length for resident stickleback of North Uist (circle) and South Uist (triangle). PC1 (71.3%) describes overall variation in spine length and pelvic size, while PC2 (13.8%) describes variation in plate number. B. Correlogram showing correlations between all measured armour traits including plate count, PC1, PC2 and standard length of North and South Uist resident fish. Blue colour denotes positive correlations where shade of the square box indicates the strength of the correlation. Measured traits were: 1stdorsal spine length (X1st.DSL), 2nd dorsal spine length (X2nd.DSL), pelvic spine length (PSL), length of pelvis (LPS), height of pelvis (HPS). Ellipses with 95% confidence intervals for each data set describing variation in four pH groups of loch water, separating the larger cluster for samples in freshwater low pH fish than the other groups.
Fig. 5 A-F Mean (± S.E.) plate count (A) and standard length (B-F) of five armour traits in 18 freshwater stickleback populations on North (circle) and South Uist (triangle).