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.

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.

Colour polymorphism can be maintained by colour morph-specific benefits across environmental conditions. Currently, the amount and duration of snow cover during winter decreases especially in northern latitudes, which can alter the potential for camouflage of animals with light and dark morphs. Tawny owls, Strix aluco, are colour polymorphic avian predators with dark (brown) and light (grey) colour morphs, where the grey morph is presumed to enjoy camouflage benefits under snowy conditions. We studied the two tawny owls’ morphs’ camouflage potential using passerines’ probability to detect and mob in the wild during spring, autumn, and winter with and without snow. We find that grey tawny owls are both less likely to be detected and have a lower probability of being mobbed compared to brown tawny owls only during snowy winters. The two colour morphs therefore experience differential benefits across snow conditions, which may help to maintain colour morphs in the population, although further warming of winter climate will reduce the potential for camouflage for grey tawny owls in northern latitudes.

In heterogeneous landscapes, habitat preference constitutes a crucial link between landscape and population-level processes such as density and sex ratios. We conducted a non-invasive genetic study of white-tailed deer in southern Finland using fecal samples. We estimated deer density as a function of landcover type using a Spatial Capture-Recapture (SCR) model. Second-order habitat selection of white-tailed deer revealed particularly high densities in fields and mixed forest, and third-order selection was related to distance to fields and transitional woodlands (clearcuts). Including landscape heterogeneity improved model fit compared with assuming a homogenous landscape. Our findings underline the importance of including habitat covariates when estimating density.

Adult sex ratio and fecundity are key population parameters in sustainable wildlife management, but inferring these requires estimates of the density of at least three age/sex classes of the population (male and female adults and juveniles). We used an array of 36 wildlife camera traps during 2–3 weeks in autumn prior to harvest during two consecutive years, and recorded white-tailed deer adult males, adult females and fawns from the pictures. Simultaneously, we collected fecal DNA (fDNA) from 92 20mx20m plots placed in 23 clusters of four plots between the camera traps. We identified individuals from fDNA samples with microsatellite markers and estimated the total sex ratio and population density using Spatial Capture Recapture (SCR). The fDNA-SCR analysis concluded equal sex ratio in the first year and female bias in the second year, and no difference in space use between sexes (fawns and adults combined). Camera information was analyzed in a Spatial Capture (SC) framework assuming an informative prior for animals’ space use, either (1) as estimated by fDNA-SCR (same for all age/sex classes), (2) as assumed from the literature (space use of adult males larger than adult females and fawns), (3) by inferring adult male space use from individually-identified males from the camera pictures. These various SC approaches produced plausible inferences on fecundity, but also inferred total density to be lower than the estimate provided by fDNA-SCR in one of the study years. SC approaches where adult male and female were allowed to differ in their space use suggested the population had a female-biased adult sex ratio. In conclusion, SC approaches allowed estimating the pre-harvest population parameters of interest and provided conservative density estimates.