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THE ORIGIN OF THE ALLOTETRAPLOID CLARKIA GRACILIS
Author(s) -
AbdelHameed Fathi,
Snow Richard
Publication year - 1972
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.1558-5646.1972.tb00175.x
Subject(s) - library science , biological sciences , history , biology , computer science , microbiology and biotechnology
The genus Clarkia, a close relative of Oenothera, is subdivided into ten sections of which Primigenia seems to be the oldest (Lewis and Lewis, 1955). This section includes six species grouped into three subsections. Subsections Primigenia and Flexicaulis contain five diploids, some of which are considered to be the most primitive members of the genus (Lewis and Lewis, 1955). Throughout the genus, the gene pools of the diploid species are without exception separated by strong barriers to gene exchange (Lewis, 1953). Lewis and Raven (1958) concluded that the accumulation of structural rearrangements, primarily reciprocal translocations, has undoubtedly played a major role in the formation of the well developed isolating mechanisms and hence to speciation at the diploid level in Clarkia. At the same time, such effective genetic isolation has apparently set the stage for the instantaneous speciation at the polyploid level through alloploidy (Lewis, 1953). Thus, it is no surprise that alloploids comprise one-third of all known Clarkia species and that natural polyploidy serves to knit the entire group together (Lewis and Lewis, 1955). Such a knitting effect is evident in section Primigenia. Clarkia gracilis (n = 14) is the only polyploid species in the section and the sole representative of subsection Jugales. It combines morphological, ecological, and chromatographic characteristics, and also the genomes of the remaining two subsections, Le., Flexicaulis and Primigenia (Abdel-Hameed, 1967). Lewis