Genomic basis of melanin-associated phenotypes suggests colour-specific
environmental adaptations in tawny owls.
Abstract
Feathers comprise a series of evolutionary innovations but also harbor
colour, a key biological trait known to co-vary with life history or
complex traits. Those relationships are particularly true in
melanin-based pigmentation species due to known pleiotropic effects of
the melanocortin pathway – originating from melanin-associated
phenotypes. Here we explore the molecular basis of melanin coloration
and expected co-variation at the molecular level in the melanin-based,
colour polymorphic system of the tawny owl (Strix aluco). An extensive
body of literature has revealed that grey and brown tawny owl colour
morphs differ in a series of life history and behavioral traits. Thus,
it is plausible to expect co-variation also at molecular level between
colour morphs. To investigate this possibility, we assembled the first
draft genome of the species against which we mapped ddRADseq reads from
220 grey and 150 brown morphs - representing 10 years of pedigree data
from a population in Southern Finland - and explored genome-wide
associations with colour phenotype. Our results revealed putative
molecular signatures of cold adaptation strongly associated with the
grey phenotype, namely a non-synonymous substitution in MCHR1, plus 2
substitutions in non-coding regions of FTCD and FAM135A whose genotype
combinations obtained a predictive power of up to 100% (predicting grey
colour). These suggest molecular basis of cold environment adaptations
predicted to be grey-morph specific. Our results potentially reveal part
of the molecular machinery of melanin-associated phenotypes and provide
novel insights towards understanding the functional genomics of colour
polymorphism in melanin-based pigmented species.