Tropicos | Name - Oenothera L.

Oenothera L.

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Project Name Data (Last Modified On 6/2/2011)

Acceptance : Accepted

Project Data (Last Modified On 6/3/2011)

Contributor Text: Peter C. Hoch and Peter H. Raven

Synonym Text: Onagra P. Miller, Gard. Dict. Abr, ed. 4: 1754; Spach, Nouv. Ann. Mus. Paris III. 4: 351. 1835; Shteinberg in Schischkin & Bobrov, Fl. URSS. 15: 628. 1949; Hartmannia Spach, Hist. VJg. Phan. 4: 378. 1835.

General/Distribution: A genus of about 125 species native to North and South America, with some species widely introduced as escapes from cultivation throughout the world. Several species are now extensively naturalized throughout many temperate regions of the world. Although the group is native only in the New World, several genetically distinctive strains have originated and subsequently become established in the Old World, following hybridization between introduced species. Many species of Oenothera, nearly all of which are weedy, are complex heterozygotes and form a ring of 14 or other large rings of chromosomes at meiotic metaphase I. Most complex heterozygotes have originated within the limits of a taxonomic species, while others have originated after hybridization between species. Genetic recombination is strongly restricted in these species on account of lethal genes or selective fertilization, predominant self-pollination, metacentric chromosomes which are involved in reciprocal translocations, and alternate disjunction at meiotic anaphase I. The two sets of 7 chromosomes behave then as if they are only a single set of chromosomes when segregating at anaphase. Therefore, any new hybridization event can, in effect, lead directly to the formation of a new 'species', whose progeny will breed true. This situation is not comparable with species recognized in most other groups of flowering plants. Represented in Pakistan by 4 naturalized or cultivated species.