title: Genetics of intrinsic postzygotic isolation in a circumpolar plant species, Draba nivalis (Brassicaceae).
abstract: Sterility barriers, ranging from incomplete to fully developed, were recently demonstrated within taxonomic species of the genus Draba, suggesting the existence of numerous, cryptic biological species. Because these taxa are predominately selfers and of Pleistocene origin, it was concluded that hybrid sterility evolved quickly and possibly by genetic drift. Here we used genetic mapping and QTL analyses to determine the genetic basis of hybrid sterility between geographically distant populations of one of these taxonomic species, Draba nivalis. Fifty microsatellite loci were mapped, and QTL analyses identified five loci underlying seed fertility and two underlying pollen fertility. Four of five seed fertility QTLs reduced fertility in heterozygotes, an observation most consistent with drift-based fixation of underdominant sterility loci. However, several nuclear-nuclear interactions were also found, including two that acted like reciprocal translocations with lowest fitness in double heterozygotes, and two that had a pattern of fitness consistent with Bateson-Dobzhansky-Muller incompatibilities. In contrast, pollen fertility QTLs exhibited additive inheritance, with lowest fertility associated with the paternal allele, a pattern of inheritance suggestive of cytonuclear incompatibilities. The results imply that multiple genetic mechanisms underlie the rapid evolution of reproductive barriers in Draba.
authors.affiliation: National Centre for Biosystematics, Natural History Museum, University of Oslo, NO-0318 Oslo, Norway. inger.skrede@nhm.uio.no
authors.forename: Inger
authors.initials: I
authors.lastname: Skrede
authors.forename: Christian
authors.initials: C
authors.lastname: Brochmann
authors.forename: Liv
authors.initials: L
authors.lastname: Borgen
authors.forename: Loren H
authors.initials: LH
authors.lastname: Rieseberg
mesh_terms: D000483:Alleles; D005075:Biological Evolution; D001937:Brassica / Q000235:genetics* / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D004843:Epistasis, Genetic; D017343:Genes, Plant; D008040:Genetic Linkage; D006579:Heterozygote; D018895:Microsatellite Repeats; D008954:Models, Biological; D008957:Models, Genetic; D018521:Plant Physiological Phenomena; D011058:Pollen; D040641:Quantitative Trait Loci; D012639:Seeds / Q000235:genetics