- Natural hybrid zones contain a wide variety of genotypes resulting frommany generations of recombination; - Stability of hybrid zones may depend on blanace between dispersal (gene flow) and selection and/or ecology; - Natural selection associated with exogenous (environmental) and/or endogenous (intrinsic genetic) factors may act on individual hybrid genotypes; - Equivalent or higher fitness of hybrids, relative to the parental taxa, has been demonstrated in many plant hybrid complexes; - Poplar (Populus sp.) hybrid zones are well known from several European river valleys; - Diploid (2n = 38) species: Populus alba, and P. tremula are differentiated morphologically and ecologically; - They reproduce sexually and vegetatively; often hybridize; are wind pollinated; seeds disperes by wind.
165.7 (Hybriden (Bastarde) (Systematische Gesichtspunkte)) 232.13 (Versuche mit Hybriden und anderen Züchtungsergebnissen [vgl. auch 165 und 232.311.3]) 176.1 (Dicotyledoneae [Siehe Anhang D])
