PHYLOGENETIC-RELATIONSHIPS AMONG THE GENERA OF THE SUBTRIBE SONCHINAE(ASTERACEAE) - EVIDENCE FROM ITS SEQUENCES

Sequences from the internal transcribed spacer region (ITS) of nuclear ribosomal DNA were used to assess relationships among genera of subtr ibe Sonchinae (Lactuceae). The data suggest that Sonchinae is paraphyl etic, and that the Dendroseridinae should not be recognized as a disti nct subtribe. Several Macaronesian genera, along with woody Macaronesi an species of Sonchus (ail diploid, 2n = 18), appear to have been deri ved from a common ancestor. Prenanthes pendula is more closely related to this Macaronesian group than to other members of Prenanthes, sugge sting that Prenanthes, Like Sonchus, is polyphyletic. The Juan Fernand ez Islands endemic genus Dendroseris (2n = 36) is monophyletic, but it s phylogenetic relationships to other Sonchinae remain uncertain. Reic hardia, which forms the sister genus of the Sonchinae, is also monophy letic. Launaea, by contrast, is considered to be paraphyletic. The mon otypic genus Aetheorhiza (2n = 18) is sister to the annual weedy speci es of Sonchus, rather than being closely related to Launaea. Two monot ypic endemic genera from New Zealand, Embergeria (2n = 36) and Kirkian ella (2n = 90, 126), are sister genera, and together they form the sis ter clade to Sonchus alvensis-S. maritimus. This implies that these Pa cific genera were derived either from section Arvenses or Maritimi of subgenus Sonchus, rather than from section Apseri.