title: Plant introductions, hybridization and gene flow.
abstract: Many regional floras contain a high proportion of recently introduced plant species. Occasionally, hybridization between an introduced species and another species (introduced or native) can result in interspecific gene flow. This may occur even in instances where the F(1) hybrid shows very high sterility, but occasionally produces a few viable gametes. We provide examples of gene flow occurring between some rhododendrons recently introduced to the British flora, and between an introduced and native Senecio species. Neutral molecular markers have normally been employed to obtain evidence of interspecific gene flow, but the challenge now is to isolate and characterize functional introgressed genes and to determine how they affect the fitness of introgressants and whether they improve adaptation to novel habitats allowing introgressants to expand the range of a species. We outline a candidate gene approach for isolating and characterizing an allele of the RAY gene in Senecio vulgaris, which is believed to have introgressed from S. squalidus, and which causes the production of ray florets in flower heads. We discuss the effects of this introgressed allele on individual fitness, including those that originate directly from the production of ray florets plus those that may arise from pleiotropy and/or linkage.
authors.affiliation: Division of Environmental and Evolutionary Biology, School of Biology, Mitchell Building, University of St Andrews, St Andrews, Fife KY16 9TH, UK. rja@st-and.ac.uk
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Abbott
authors.forename: Juliet K
authors.initials: JK
authors.lastname: James
authors.forename: Richard I
authors.initials: RI
authors.lastname: Milne
authors.forename: Amanda C M
authors.initials: AC
authors.lastname: Gillies
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D005075:Biological Evolution; D005819:Genetic Markers; D006824:Hybridization, Genetic; D011157:Population Dynamics; D012674:Senecio / Q000235:genetics* / Q000502:physiology; D013045:Species Specificity; D006113:United Kingdom
chemical_list: D005819:Genetic Markers