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Taxonomy of Cyanastroideae (Tecophilaeaceae): A Multidisciplinary Approach

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Cyanastrum has previously been considered to include four species, all from the African continent. One of these, C. hostifolium from eastern Tanzania and northern Mozambique, is now transferred to a new genus, Kabuyea (K. hostifolia). This differs from Cyanastrum in several respects: vegetative morphology, perianth colour, anther dehiscence, pollen grain morphology, seed structure, chromosome number and karyotype. Karyotype analysis indicates that the individuals examined of the new genus are triploids. Analysis of rbcL DNA sequences for Cyanastraceae and Tecophilaeaceae places K. hostifolia as sister to G cordifolium, but the level of sequence divergence between these two species is similar to that between genera in Tecophilaeaceae. The presence of a 'chalazosperm' in seeds of Cyanastrum was the primary reason for former recognition of the monogeneric family Cyanastraceae, but this structure is absent from seeds of Kabuyea. Relationships of Cyanastrum and Kabuyea with other Tecophilaeaceae are discussed.
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