Sammendrag
Coloration is evolutionarily labile and so provides an excellent trait for examining the repeatability
of evolution. Here, we investigate the repeatability of the evolution of polymorphic variation in
ventral plumage coloration in skuas (Stercorarius: Stercorariidae). In 2 species, arctic (S. parasiticus)
and pomarine skuas (S. pomarinus), plumage polymorphism was previously shown to be
associated with coding changes at the melanocortin-1 receptor (MC1R) locus. Here, we show that
polymorphism in a third species, the south polar skua (S. maccormicki), is not associated with
coding variation at MC1R or with variation at a Z-linked second candidate locus, tyrosinase-related
protein 1 (TYRP1). Hence, convergent evolution of plumage polymorphisms in skuas is only partly
repeatable at the level of the genetic locus involved. Interestingly, the pattern of repeatability in
skuas is aligned not with phylogeny but with the nature of the phenotypic variation. In particular,
south polar skuas show a strong sex bias to coloration that is absent in the other species, and it
may be that this has a unique genetic architecture.
Genotype to phenotype
MC1R, melanin, repeatability of evolution, skua, TYRP1
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