title: Ancient origin and maternal inheritance of blue cuckoo eggs.
abstract: Maternal inheritance via the female-specific W chromosome was long ago proposed as a potential solution to the evolutionary enigma of co-existing host-specific races (or 'gentes') in avian brood parasites. Here we report the first unambiguous evidence for maternal inheritance of egg colouration in the brood-parasitic common cuckoo Cuculus canorus. Females laying blue eggs belong to an ancient (∼2.6 Myr) maternal lineage, as evidenced by both mitochondrial and W-linked DNA, but are indistinguishable at nuclear DNA from other common cuckoos. Hence, cuckoo host races with blue eggs are distinguished only by maternally inherited components of the genome, which maintain host-specific adaptation despite interbreeding among males and females reared by different hosts. A mitochondrial phylogeny suggests that blue eggs originated in Asia and then expanded westwards as female cuckoos laying blue eggs interbred with the existing European population, introducing an adaptive trait that expanded the range of potential hosts.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.
authors.forename: Frode
authors.initials: F
authors.lastname: Fossøy
authors.affiliation: Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Sorenson
authors.affiliation: Ministry of Education, College of Life Sciences, Hainan Normal University, Haikou 571158, China.
authors.forename: Wei
authors.identifier: http://orcid.org/0000-0002-0004-9707
authors.initials: W
authors.lastname: Liang
authors.affiliation: Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Ekrem
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.
authors.forename: Arne
authors.initials: A
authors.lastname: Moksnes
authors.affiliation: Ecologie, Systématique et Evolution, UMR 8079 CNRS, F-91405, Orsay Cedex; Université Paris-Sud 11, F-91405, Orsay Cedex, AgroParisTech, F-91405 Orsay, France.
authors.forename: Anders P
authors.initials: AP
authors.lastname: Møller
authors.affiliation: Department of Biology, University of Eastern Finland, FI-80101 Joensuu, Finland.
authors.forename: Jarkko
authors.initials: J
authors.lastname: Rutila
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.
authors.forename: Eivin
authors.initials: E
authors.lastname: Røskaft
authors.affiliation: Department of Information and Computer Sciences, Nara Women's University, Kita-Uoya, Nishimachi, Nara 630-8506, Japan.
authors.forename: Fugo
authors.initials: F
authors.lastname: Takasu
authors.affiliation: Ministry of Education, College of Life Sciences, Hainan Normal University, Haikou 571158, China.
authors.forename: Canchao
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.
authors.forename: Bård G
authors.initials: BG
authors.lastname: Stokke
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D004528:Egg Shell; D004531:Eggs; D005260:Female; D010641:Phenotype; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics*; D012730:Sex Chromosomes / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial