Categories: Pigmentation phene

Mendelian trait/disorder: yes

Mode of inheritance: Z-linked

Disease-related: no

Key variant known: no

Key variant is published: no

Species-specific name: Toomey et al. (2028): "Gouldian finch is endemic to Australia and throughout its range two common colour morphs, black and red head colour, coexist at a ratio of approximately 7 : 3 ... [Franklin and Dostine, 2000]. A third orange morph occurs at very low frequency (less than 0.1%). These head-colour morphs also have distinct physiological and behavioural phenotypes. Red morphs tend to be aggressive and dominant over black morph individuals in agonistic encounters and have a heightened physiological response to social stress [Pryke, 2007; Pryke et al., 2006, 2007]. Red morphs substantially increase circulating sex steroid (testosterone) and stress hormone (corticosterone) levels in competitive social environments, while black morphs show no such response [Pryke et al., 2007]."

Inheritance: Toomey et al. (2018): "The suite of morphological, behavioural and physiological traits associated with head-colour morph are determined by a sex-linked Mendelian locus where red (ZR) is the dominant allele and black (Zr) is recessive [Southern, 1945]. The orange head-colour morph is determined by an autosomal locus."

Mapping: Toomey et al. (2018): "the Red locus was mapped to an approximately 7.2 cM interval on the Z chromosome using microsatellite markers [Kim et al., 2016]". Toomey et al. (2018) created a reference genome for the Gouldian finch and showed "that the red and black morphs have nearly identical genome sequences, and that genetic differences between morphs are restricted to a relatively small genomic interval that was found to be perfectly associated with the head-colour polymorphism. This interval is in a non-coding region upstream of FST." The authors "suggest that the distinct feather colour and morphology of the two morphs may be the product of cis-regulatory differences that drive differential expression of FST during a discrete period early in feather development/regeneration." Kim et al. (2019) reported similar results, namely "that differences in colour [at the Red locus] are associated with an ~72-kbp region of the Z chromosome in a putative regulatory region for follistatin, an antagonist of the TGF-β superfamily genes. The region is highly differentiated between morphs, unlike the rest of the genome, yet we find no evidence that an inversion is involved in maintaining the distinct haplotypes".