Sunflower family tree (IMAGE)
Caption
A new sunflower family tree reveals that flower symmetry evolved multiple times independently. Species of the sunflower family with or without bilateral flower symmetry. Chrysanthemum lavandulifolium (upper left) and Artemisia annua (upper right) are closely related species from the same tribe; the former has bilaterally symmetric flowers (the rays) and the latter does not. Rudbeckia hirta (lower left) from the sunflower tribe has bilaterally symmetric flowers, and Eupatorium chinense (lower right) from the Eupatorieae tribe does not; these two tribes are closely related groups. A sunflower (center) shows flowers with bilateral symmetry (the large petal-like flowers in the outer row) and without (the small flowers in the inner rows).
Credit
Guojin Zhang, Ma laboratory, Penn State
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License
CC BY-NC-ND