Baião Patricia C, Schreiber Ea, Parker Patricia G
Department of Biology, University of Missouri-St Louis, One University Boulevard, R223, St Louis, MO 63121, USA.
J Hered. 2007 Jul-Aug;98(4):287-92. doi: 10.1093/jhered/esm030. Epub 2007 Jun 29.
The red-footed booby (Sula sula) is considered one of the most polymorphic seabirds, with 3 recognized major adult plumage types: 1) white, 2) white-tailed brown, and 3) brown and several degrees of intermediates. Here we show that the white/melanic polymorphism observed in this species is perfectly associated with 2 point substitutions, Val85Met and His207Arg, at the melanocortin-1 receptor (MC1R) gene. Among the melanic plumage variants, we also found a strong association between the degree of melanism and the number of copies of variant MC1R alleles. Furthermore, the Val85Met point substitution has been previously shown to be associated with melanic phenotypes in the lesser snow goose (Anser c. caerulescens), suggesting parallel evolution of the melanic allele, and hence, melanism, between these 2 distantly related species. We also compared the MC1R locus in red-footed boobies with a nonpolymorphic congener, the Nazca booby (Sula granti), in which all adults are white. We found that Nazca boobies present the same genotype at sites 85 and 207 as white morph red-footed boobies.
红脚鲣鸟（Sula sula）被认为是多态性最高的海鸟之一，有3种公认的主要成年羽色类型：1）白色，2）白尾棕色，3）棕色以及几种程度的中间类型。在此我们表明，在该物种中观察到的白色/黑色多态性与黑皮质素-1受体（MC1R）基因上的2个点突变，即Val85Met和His207Arg，完全相关。在黑色羽色变体中，我们还发现黑化程度与变异MC1R等位基因的拷贝数之间存在很强的相关性。此外，之前已表明Val85Met点突变与小雪雁（Anser c. caerulescens）的黑色表型相关，这表明这两个远缘物种之间黑色等位基因，进而黑化现象，存在平行进化。我们还将红脚鲣鸟的MC1R基因座与一个非多态性的同属物种——纳斯卡鲣鸟（Sula granti）进行了比较，纳斯卡鲣鸟的所有成年个体都是白色的。我们发现，纳斯卡鲣鸟在第85和207位点的基因型与白色形态的红脚鲣鸟相同。
