Allopolyploidy of Subtribe Tussilagininae (Asteraceae: Senecioneae)

The subtribe Tussilagininae (Asteraceae: Senecioneae) has a rich species diversity (45 genera and about 710 species) and high base chromosome numbers (mainly x = 30, 40). This study reveals the complex allopolyploid pattern of this group, and the result is particularly strongly supported by the evidence of base chromosome numbers. Tussilagininae comprises two large groups with successive allopolyploid origins: Tussilagininae s.s. (mainly x = 30) and the Gynoxyoid group (x = 40). Two allopolyploidy events first give rise to Tussilagininae s.s., with the first event occurring between the ancestor of subtribe Senecioninae (x = 10) and a lineage (highly probably with x = 10) related to the Brachyglottis alliance, and the resulting hybrid lineage crossing with the ancestor of Chersodoma (x = 10) and leading to Tussilagininae s.s. Then, after early diversification, the Central American group (mainly x = 30) of Tussilagininae s.s., is involved in a third allopolyploidy event with, again, the Chersodoma lineage and produces the Gynoxyoid group.