Evolution of Illicium (Illiciaceae): Mapping morphological characters on the molecular tree
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Illicium is a member of the ANITA grade and as such represents one of the basalmost lineages of flowering plants. Mapping morphological characters on a recently published molecular tree sheds some light on the conflict between the traditional classification of Illicium based on floral structures and the molecular based phylogeny. Floral characters of Illicium, i.e. number, size, and shape of perianth segments, stamens, and carpels, are highly variable. In Illicium sepaloid perianth segments intergrade with petaloid ones. This is also observed in the other ANITA taxa, where gradations from bracts to perianth segments and stamens occur, but not in more derived plant groups, and indicates that the number of floral organs may not be genetically fixed in basal angiosperms. Therefore, floral characters may have evolved in parallel in different groups of Illicium and, taken alone, may be unsuitable for a subgeneric division of Illicium. In contrast, seed structures such as the hilar area and a conspicuous hilar rim structure found in New World species of Illicium support a major division between New World and Old World species of Illicium as suggested by molecular data. Epidermal features generally are uniform within the genus but provide some support for one of the clades recognized in the molecular tree. In general, few morphological characters can be used to distinguish natural species groups within Illicium.
KeywordsIllicium star anise seed morphology leaf epidermis hilar rim fossil seeds evolution
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