Candidate genes
From a total of 132,343 SNPs, 115 showed absolute loading scores on the
RDA1 and RDA2 distributions deviating from the mean by more than six
times the standard deviation. Out of these 115 loci, the 2000-bp
flanking region of 23 of them (20%) mapped against a total of 15
annotated genes. Potentially relevant reported functions of the
identified genes in vertebrates included the following: heart and muscle
development (DPF3; Lange et al. 2008); heavy metal sensitiveness
and detoxification (ABCB6; Rakvács et al. 2019); high-pitched
hearing (KCNQ4; Liu et al. 2011); laying performance and egg
quality (IOV7; Huang et al. 2019; Wu et al. 2018); DNA
crosslink repair and tolerance to UV light and camptothecin-induced DNA
damage (FANCM; Rosado et al. 2009); megakaryocytopoiesis,
platelet formation (TPOR; Ocampo Daza & Larhammar 2018); trait
regulation of energy balance through effects on feeding behavior and
adaptive thermogenesis (KSR2; Guo et al. 2017); and modulation of
fasting blood glucose (G6PC2; Matschinsky 2005; O’Brien 2013), possibly
in response to stress (Boortz et al. 2016). PairwiseF ST values based on SNP loci linked to functional
candidate genes revealed relative patterns of differentiation similar to
those based on neutral markers, but yielded considerably higher absolute
values. UCSD showed the highest pairwise F STscores with isolated forms townsendi (0.54) and pontilis(0.28), an average of 0.32 with northern forms, and the lowest value
with pinosus (0.21) (Table 2). Per-locusF ST values between UCSD and the sister grouppinosus showed moderate to high levels of divergence (0.26 to
0.51) in genes TPOR, ABCB6, FANCM, KCNQ4 and IOV7, with the rest of the
genes ranging from 0 to 0.2 F ST values (Table S2,
Supporting Information).