title: Hybridization and introgression in a mixed population of the intertidal seaweeds Fucus evanescens and F. serratus.
abstract: The introduced Fucus evanescens (hermaphroditic) and the native F. serratus (dioecious) have been in secondary contact along the Danish coast of the Kattegat Sea for 60-100 years and dioecious hybrids have been observed at Blushøj for several years. Hybridization in Fucus is unusual because it appears to always involve a hermaphroditic and a dioecious parental pair. We determined the degree and spatial patterns of introgression for 286 individuals using 10 microsatellite loci and cpDNA. Hybrids accounted for nearly 13% of the population, yet parental species were well differentiated (F(ST) = 0.633). The presence of F. evanescens chloroplasts in 100% of F(1) hybrids revealed asymmetrical hybridization. Fucus evanescens cpDNA was observed in 50% of introgressed and 5.4% of pure F. serratus, but no F. serratus cpDNA was found in F. evanescens. In contrast, nuclear DNA introgression was symmetrical with an equal amount ( approximately 1.5%) of genes introgressed into each parental species. Survivorship and viability data suggest selection against hybrids in the hybrid zone.
authors.affiliation: Department of Benthic Ecology and Evolution, Centre for Ecological and Evolutionary Studies, University of Groningen, AA Haren, The Netherlands. j.a.coyer@rug.nl
authors.forename: J A
authors.initials: JA
authors.lastname: Coyer
authors.forename: G
authors.initials: G
authors.lastname: Hoarau
authors.forename: W T
authors.initials: WT
authors.lastname: Stam
authors.forename: J L
authors.initials: JL
authors.lastname: Olsen
mesh_terms: D018742:DNA, Chloroplast / Q000235:genetics; D044645:Fucus / Q000235:genetics*; D006824:Hybridization, Genetic; D012624:Seaweed / Q000235:genetics*
chemical_list: D018742:DNA, Chloroplast