Studies in asteraceae : nuclear ribosomal DNA and macaronesian endemics
The phylogenetic and biogeographical history of the Asteriscus alliance in Macaronesia was investigated with DNA sequence data from the nuclear and chloroplast genomes. Relationships among taxa were fully resolved by combining data from these sources. The alliance is divided into two groups, the monophyletic genus Pallenis, and a larger clade containing Asteriscus and the monotypic Ighermia. The direction of island colonization events is difficult to infer because of the wide distributions assumed for ancestral taxa. ITS sequences from related Inuleae and other species of Asteraceae were used to derive a secondary structure model by comparative analyses. Tribal relationships reconstructed from the resulting alignment show considerable congruence with previous molecular and morphological studies and demonstrate the retention of deep phylogenetic signal in ITS sequence data. Incongruence between Argyranthemum nuclear and chloroplast data was assessed as part of an investigation into hybridization in this Macaronesian endemic genus. ETS sequence data are incongruent with chloroplast restriction site data but the differences are more likely due to insufficient phylogenetic signal than different evolutionary histories.