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Taxon Biology

Much of the material for this page is taken from Funk & Fragman-Sapir (2009).

Gymnarrhena is an unusual member of the Compositae (Asteraceae). It is an ephemeric, amphicarpic, dwarf desert annual. Amphicarpic plants have two types of flowers, in this case aerial casmogamous heads and subterranean cleistogamous ones, and the different flowers produce different fruits. In Gymnarrhena, the achenes produced from these two types of inflorescence and the seedlings that germinate from them, differ in size, morphology, physiology and ecology (Koller & Roth, 1964; Zamski et al., 1983). The plant is very small and has grass-like leaves, the aerial heads are clustered together and have functional male and female florets. The familiar parts of the Compositae head have been modified extensively and most of the usual identifying features are missing or altered (see images). Currently there is one species recognized, Gymnarrhena micrantha Desf., however there is some variation across the distribution and it should be investigated further.

Historical overview

As might be imagined the history of this taxon reflects its unusual morphology. Bentham (1873), Hoffmann (1894), and Cronquist (1955) put this genus in the Inuleae s.l. Hoffmann and Cronquist both mention the similarity to Geigeria; Bentham’s alternate choice was the Astereae. Small (1917-1979) considered the Inuleae to be linked to Centaurea of the Cardueae. Leins (1973) in his examination of the pollen of the Inuleae stated that Gymnarrhena did not belong in that tribe and suggested the Cynareae-Carlininae. Merxmuller et al. (1977) agareed that Gymnarrhena was not in the Inuleae and cited Leins (1973). Skvarla (1977) acknowledged a superficial resemblance between Gymnarrhena and the Cardueae but pointed out that it had Anthemoid type pollen (also found in the Senecioneae and other tribes) and did not belong in the Inuleae or Astereae. Skvarla further acknowledged that, based on the pollen, the genus was difficult to place. Bremer (1994) listed the genus as belonging to the Cichorioideae s.l. but as “unassigned to tribe” along with several other problem genera.

Systematics – Molecular Phylogeny

Anderberg et al. (2005) in a study of the Inuleae using ndhF determined that Gymnarrhena did not belong in the Asteroideae but rather was part of the then paraphyletic Cichorioideae s.l. or sister to the entire Asteroideae. In the most recent broad scale cladograms Gymnarrhena is in a clade by itself and is consistently located below the Cichoroideae s.s. – Corymbieae – Asterioideae clade and above the Carduoideae and Pertyoideae clades (Panero & Funk 2002, 2008; Funk et al. 2009). Its position means that it cannot be placed in any of the other suprageneric taxa and is now recognized as an independent lineage. This position is supported by the fact that Gymnarrhena lacks the ‘9 base pair deletion’ in the ndhF gene identified by Kim and Jansen (1995) and subsequently used by Bremer (1996) as a molecular characteristic in support of the recognition of the Cichorioideae-Chorymboideae/Asterioideae clade. In the most recent taxanomic overview for the family the tribe Gymnarrhenaeae was accepted by Jeffrey (2006) based on the molecular results reported above.

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© Funk, Vicki

Source: Compositae

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