Department of Population Biology and Conservation Biology, Uppsala University, Uppsala, Sweden.
PLoS One. 2010 Apr 23;5(4):e10334. doi: 10.1371/journal.pone.0010334.
Population variation in the degree of seasonal polymorphism is rare in birds, and the genetic basis of this phenomenon remains largely undescribed. Both sexes of Scandinavian and Scottish Willow grouse (Lagopus lagopus) display marked differences in their winter phenotypes, with Scottish grouse retaining a pigmented plumage year-round and Scandinavian Willow grouse molting to a white morph during winter. A widely studied pathway implicated in vertebrate pigmentation is the melanin system, for which functional variation has been characterised in many taxa.
METHODOLOGY/PRINCIPAL FINDINGS: We sequenced coding regions from four genes involved in melanin pigmentation (DCT, MC1R, TYR and TYRP1), and an additional control involved in the melanocortin pathway (AGRP), to investigate the genetic basis of winter plumage in Lagopus. Despite the well documented role of the melanin system in animal coloration, we found no plumage-associated polymorphism or evidence for selection in a total of approximately 2.6 kb analysed sequence.
CONCLUSIONS/SIGNIFICANCE: Our results indicate that the genetic basis of alternating between pigmented and unpigmented seasonal phenotypes is more likely explained by regulatory changes controlling the expression of these or other loci in the physiological pathway leading to pigmentation.
鸟类季节性多态性程度的种群差异很少见，这种现象的遗传基础在很大程度上仍未被描述。斯堪的纳维亚和苏格兰松鸡（Lagopus lagopus）的雌雄两性在冬季表型上存在明显差异，苏格兰松鸡全年保留有色羽毛，而斯堪的纳维亚柳鸡在冬季则蜕皮为白色形态。一个广泛研究的涉及脊椎动物色素沉着的途径是黑色素系统，许多分类群的功能变异已经在这个系统中得到了描述。
方法/主要发现：我们对涉及黑色素生成的四个基因（DCT、MC1R、TYR 和 TYRP1）和一个涉及黑色素皮质素途径的额外控制基因（AGRP）的编码区进行了测序，以研究拉戈普斯冬季羽毛的遗传基础。尽管黑色素系统在动物颜色形成中的作用已有充分的记录，但我们在总共约 2.6kb 的分析序列中没有发现与羽毛相关的多态性或选择证据。
结论/意义：我们的结果表明，在有色素和无色素季节性表型之间交替的遗传基础更可能是通过调节控制这些或其他基因座在导致色素形成的生理途径中的表达的变化来解释的。
