Divergent sorting of a balanced ancestral polymorphism underlies the establishment of gene-flow barriers in Capsella.
In the Bateson-Dobzhansky-Muller model of genetic incompatibilities post-zygotic gene-flow barriers arise by fixation of novel alleles at interacting loci in separated populations. Many such incompatibilities are polymorphic in plants, implying an important role for genetic drift or balancing selection in their origin and evolution. Here we show that NPR1 and RPP5 loci cause a genetic incompatibility between the incipient species Capsella grandiflora and C. rubella, and the more distantly related C. rubella and C. orientalis. The incompatible RPP5 allele results from a mutation in C. rubella, while the incompatible NPR1 allele is frequent in the ancestral C. grandiflora. Compatible and incompatible NPR1 haplotypes are maintained by balancing selection in C. grandiflora, and were divergently sorted into the derived C. rubella and C. orientalis. Thus, by maintaining differentiated alleles at high frequencies, balancing selection on ancestral polymorphisms can facilitate establishing gene-flow barriers between derived populations through lineage sorting of the alternative alleles.
Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, Haus 26, 14476 Potsdam-Golm, Germany.
Adrien
A
Sicard
Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, Haus 26, 14476 Potsdam-Golm, Germany.
Christian
C
Kappel
Department of Ecology &Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
Emily B
EB
Josephs
Department of Ecology &Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
Young Wha
YW
Lee
Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, Haus 26, 14476 Potsdam-Golm, Germany.
Cindy
C
Marona
Department of Ecology &Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
John R
JR
Stinchcombe
Department of Ecology &Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2.
Stephen I
SI
Wright
Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, Haus 26, 14476 Potsdam-Golm, Germany.
Michael
M
Lenhard
D000483:Alleles; D001426:Bacterial Proteins; D005075:Biological Evolution; D029687:Capsella / Q000235:genetics*; D005098:Exotoxins; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D051456:Gene Flow / Q000502:physiology*; D006239:Haplotypes; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011110:Polymorphism, Genetic; D012641:Selection, Genetic
D001426:Bacterial Proteins; D005098:Exotoxins; D008565:Membrane Proteins; D010940:Plant Proteins; C117980:SpeA protein, Streptococcus pyogenes