Barnadesia caryophylla (Vell.) S.F.Blake (Asteraceae)


 Inflorescence of  Barnadesia caryophylla growing in the Oxford Botanic Garden.  Specimen of Barnadesia caryophylla collected by George Gardner in Goiás (Brazil) in 1840 (Oxford University Herbaria).

Barnadesia is a small (18 species), wholly South American genus with the vast majority of its species found along the Andean Cordillera. Barnadesia caryophylla is a spiny shrub, native to woodlands and scrub, from 600 m to 2,700 m altitude, in Peru, Bolivia and Brazil; it is the sole Brazilian species in the genus. Barnadesia caryophylla was first described from an illustration, and hence the species' type, is a line drawing published, in 1831, in José de Conceição Vellozo's part work Flora Fluminensis. Velloso's work has the distinction of being dismissed by Carl von Martius, architect of Brazil's standard flora (Flora Brasiliensis, 1840-1906), as a 'monstrous example of an ill-advised and overambitious literary enterprise' and by Sir William Hooker, nineteenth-century Director of the Royal Botanic Gardens Kew, as a 'magnificent abortion'.

As a glasshouse plant, Barnadesia caryophylla can reach 4 m in height and flowered in Britain, in the Duke of Northumberland's collection, before 1843. Although it is rarely grown, Barnadesia caryophylla attracts the attention of European gardeners because of the distinctive needle-like, paired spines, up to 3 cm long, arranged along the plant's stem and the large pink, red or purple flower heads (capitula), up to 5 cm long and 3 cm wide. Like the sunflower, Barnadesia capitula are composed of numerous silky-haired, tubular flowers packed closely together and surrounded by rows of long, narrow scales. The large quantities of sweet, sticky nectar produced by the capitula, together with field observations, have led researchers to propose that Barnadesia species are bird pollinated - by hummingbirds; a strategy rarely found in the Asteraceae.

Barnadesia and related genera in the subfamily Barnadesioideae were important in establishing that DNA characteristics could be used to understand plant evolution. In the late 1980s, using a laborious technique for comparing chloroplast DNA (cpDNA) structure, a group of researchers found the Barnadesioideae lacked a large, rare structural mutation (inversion) present in other members of the Asteraceae. The inversion was also absent from all other flowering plants investigated outside of the Asteraceae. This showed the Barnadesioideae were the most basal group in the Asteraceae and changed our ideas of Asteraceae classification. Subsequent research has precisely located the inversion in the cpDNA, and shown it probably occurred once 38-42 million years ago.

The name Barnadesia commemorates the eighteenth-century Spanish botanist and royal physician Miguel Barnades, who was instrumental in promoting Carolus Linnaeus's ideas of plant classification in Spain.

Further reading

Jansen RK & Palmer JD 1987. A chloroplast DNA inversion marks an ancient evolutionary split in the sunflower family (Asteraceae). Proceedings of the National Academy of Sciences USA 84, 5818-5822.

Jansen RK & Palmer JD 1988. Phylogenetic implication of chloroplast DNA restriction site variation in the Mutisieae (Asteraceae). American Journal of Botany 75, 753-766.

Urtubey E 1999. Revisión del género Barnadesia (Asteraceae: Barnadesioideae, Barnadesieae). Annals of the Missouri Botanical Garden 86, 57-117.

Stephen Harris