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).