title: Parental ploidy strongly affects offspring fitness in heteroploid crosses among three cytotypes of autopolyploid Jacobaea carniolica (Asteraceae).
abstract: Reproductive interactions among cytotypes in their contact zones determine whether these cytotypes can co-exist and form stable contact zones or not. In autopolyploids, heteroploid cross-compatibilities might depend on parental ploidy, but tests of this hypothesis in autopolyploid systems with more than two ploidies are lacking. Here, we study Jacobaea carniolica, which comprises diploid, tetraploid, and hexaploid individuals regularly forming contact zones. Seeds obtained from in situ cross-pollinations within and among cytotypes were subjected to DNA flow cytometry and greenhouse germination experiments. Hybrid fitness and parental effects on hybrid fitness were tested with regression models comparing fitness parameters of early life stages. Irrespective of the direction of crosses, seed viability and seedling survival in diploid-polyploid crosses were substantially lower than in tetraploid-hexaploid crosses. In contrast, seedling growth traits indicated neither transgressive character expression nor any selection against hybrid offspring. Congruent with a model of genome dosage effects, these traits differed between reciprocal crosses, especially of diploids and tetraploids, where trait values resembled those of the maternal parent. The strong effect of parental ploidy on offspring fitness in heteroploid crosses may cause contact zones involving exclusively polyploid cytotypes to be less stable over longer terms than those involving diploids and polyploids.
authors.affiliation: Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria ; Department of Conservation Biology, Vegetation Ecology and Landscape Ecology, University of Vienna, Vienna, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Sonnleitner
authors.forename: Birgit
authors.initials: B
authors.lastname: Weis
authors.forename: Ruth
authors.initials: R
authors.lastname: Flatscher
authors.forename: Pedro Escobar
authors.initials: PE
authors.lastname: García
authors.forename: Jan
authors.initials: J
authors.lastname: Suda
authors.forename: Jana
authors.initials: J
authors.lastname: Krejčíková
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Schneeweiss
authors.forename: Manuela
authors.initials: M
authors.lastname: Winkler
authors.forename: Peter
authors.initials: P
authors.lastname: Schönswetter
authors.forename: Karl
authors.initials: K
authors.lastname: Hülber
mesh_terms: D019659:Asteraceae / Q000235:genetics* / Q000502:physiology; D056625:Endosperm / Q000235:genetics; D056084:Genetic Fitness; D006824:Hybridization, Genetic; D054817:Pollination / Q000235:genetics; D011123:Polyploidy; D036226:Seedlings / Q000235:genetics