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GENETICAL POPULATION STRUCTURE IN PLANTS: GENE FLOW BETWEEN DIPLOID SEXUAL AND TRIPLOID ASEXUAL DANDELIONS ( TARAXACUM SECTION RUDERALIA )
Author(s) -
Menken Steph B. J.,
Smit Eric,
Nijs Hans J. C. M. Den
Publication year - 1995
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1995.tb04437.x
Subject(s) - biology , apomixis , ploidy , gene flow , population , asexual reproduction , basidium , meiosis , sexual reproduction , polyploid , botany , gene pool , genetics , genetic variation , genetic diversity , gene , spore , demography , sociology
Levels and distribution of genetic variation were studied in central and western European populations of Taraxacum section Ruderalia containing differing mixtures of sexual diploid and asexual triploid plants. All sexual populations were panmictic with their variation partitioned mainly among populations. Genotypic diversity in triploid samples was very high with few clones widespread and many clones restricted to one or a few populations. Extensive amounts of gene (pollen) flow between the diploid and triploid components of a population were inferred from the following data: (1) the two ploidy levels share all major allozyme polymorphisms; (2) the intrapopulational homogeneity in genic variation between diploids and triploids contrasts strongly with the geographic differentiation at each ploidy level separately; (3) population‐unique alleles simultaneously occur at the two ploidy levels; (4) not only sexuals but also asexuals generally simulate Hardy‐Weinberg expectations. Most likely, intrapopulational gene exchange occurs bidirectionally by mechanisms such as reductional pollen meiosis in apomictic plants, facultative apomixis, and formation of unreduced gametes in sexuals. Thus, diploid and triploid Taraxacum section Ruderalia are less genetically isolated than has previously been supposed and probably form a cohesive evolutionary unit with the level at which gene pools are shared differing by population.