Genomic basis of melanin-phenotypes indicates colour-specific
environmental adaptations in tawny owls
Abstract
Feathers comprise a series of evolutionary innovations but also harbor
colour, a biological trait with immense selective value and known to
co-vary with life history or complex traits. Such an intricate web of
relationships is particularly true in melanin-based pigmentation
species, mainly due to known pleiotropic effects of the melanocortin
pathway – originating so-called melanin-phenotypes. Here we explored
the molecular basis of melanin coloration and expected co-variation at
molecular level in a melanin-based, colour polymorphic benchmark system,
the tawny owl. An extensive body of literature has revealed grey and
brown tawny owl color morphs differ in a series of life history and
behavioral traits. 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 molecular signatures of cold adaptation
strongly associated with grey coloration, namely a non-synonymous
substitution in MCHR1 detected when comparing genomes, 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). All these genes have functions related to energy homeostasis,
fat deposition and control of starvation response and indicate the
molecular basis of some cold environment adaptations predicted to be
grey-morph specific. our results unveil part of the molecular machinery
of melanin-phenotypes and shed light on the maintenance and evolution of
colour polymorphism in melanin-based pigmented species.