Figure 1 – (a) Content mg/g of ALA and EPA in aquatic
and terrestrial prey macroinvertebrates. All prey samples contained no
or negligible amount of DHA. Association of the reliance on terrestrial
prey and the relative content of ALA (b), EPA (c), and DHA (d) in trout
tissues. Colours of datapoints, fit lines and box plots displaying
distribution of each variable correspond to AF – allopatric females
(red), AM – allopatric males (green), SF - sympatric females (cyan),
and SM – sympatric males (purple). Variables in figures b-d are
residuals controlled for the fork length of individuals.
Total brain volume increased with increasing DHA content in trout
tissues (F1,80 = 11.57, p = 0.001, Fig. 2a), but DHA
content had no effect on brain morphology (PC 1: F1,80 =
0.92, p = 0.341, Fig. 2b; PC2: F1,80 = 3.89, p = 0.052,
Fig. 2c). Total lipids content in trout tissues had no significant
effect on total brain volume (F1,81 = 2.92, p = 0.092)
and morphology (PC 1: F1,81 = 1.27, p = 0.263; PC2:
F1,81 = 3.94, p = 0.051). The brain volume increased
with increasing fork length of individuals (F1,80 =
657.45, p < 0.001), but brain morphology was independent of
individual fork length (PC 1: F1,81 = 0.07, p = 0.786;
PC2: F1,80 = 0.01, p = 0.943). Brain volume and brain
morphology did not differ between allopatric and sympatric populations
(brain volume: F1,80 = 0.51, p = 0.476; PC 1:
F1,80 = 0.99, p = 0.322; PC2: F1,80 =
0.00, p = 0.990) or between the sexes (brain volume:
F1,80 = 1.54, p = 0.219; PC 1: F1,81 =
0.57, p = 0.454; PC2: F1,80 = 0.05, p = 0.943).