Silversword alliance Asteraceae

A North American origin for the silverswords clearly emerged from the application of DNA-sequence techniques to members of the alliance and representative Californian species (Baldwin et al., 1990, 1991). The conclusions from these studies, based on chloroplast restriction site analysis were subsequently corroborated by ITS nuclear ribosomal DNA studies. A comprehensive review of these studies can be found in Carlquist et al. (2003). 

Perhaps the most useful contribution made by flavonoids in this group of plants, however, was the assistance they provided in studies of natural hybridization between Dubautia scabra and D. ciliolata (Crins et al., 1988a). Dubautia scabra is a pioneer plant that colonizes new lava moderately D. ciliolata occurs on somewhat older lava. Where newer flows overlap older ones, one can often find plants with features intermediate between the two species. This phenomenon is readily observed in the vicinity of Kilauea Volcano on the island of Hawaii, where one finds D. scabra subsp. scabra on newer substrate and D. ciliolata subsp. glutinosa on the older substrate. Since the two taxa exhibit different flavonoid profiles, and we know that flavonoid profiles are inherited in an additive fashion, hybrids would be expected to exhibit flavonoid markers inherited from each parent. A major advantage in this study was the availability of known Fj hybrids that had been produced from controlled crosses at the University of Hawaii (by G. D. Carr). Analysis of the 

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Baldwin, B. G., Kyhos, D. W. and Dvolrak, J. 1990. Chloroplast DNA evolution and adaptive radiation in the Hawaiian silversword alliance (Asteraceae—Madiinae). Ann. Missouri Bot. Gard. 77 96-109. 

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