Karyotype evolution and chromosome numbers in Chrysopsis (Nutt.) Ell. sensu Semple (Compositae–Astereae)

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Abstract
The karyotypes of all species of Chrysopsis were analysed and four basic complements were recognised. The X = 5 karyotype was possessed by all seven n = 5 species and consisted of three submetacentric and two acrocentric chromosomes, one bearing the nucleolar organizer region medially on its short arm. Each X = 4 species had a distinct karyotype. The n = 4 karyotype of C. mariana had diverged less from the X = 5 karyotype than that of C. pilosa. The X2 = 9 karyotype shared by three n = 9 taxa was found to be little more than a combination of the X = 5 karyotype and the X = 4 mariana karyotype and was therefore of allopolyploid origin. Some shifting in the location of the nucleolar organizer region has occurred in each group.