Evidence for a Close Relationship Between Iostephane and Viguiera (Asteraceae: Heliantheae)

Abstract

The phylogenetic relationship of Iostephane is assessed using data from morphology, flavonoid chemistry, and chloroplast DNA and nuclear ribosomal DNA restriction fragment analysis. Morphological evidence supports placement of Iostephane in subtribe Helianthinae, but fails to clarify the placement of the genus within this assemblage. Further evidence for the placement of Iostephane in subtribe Helianthinae is provided by the presence in all species of the genus of floral flavonoids of the chalcone/aurone type, which provides a distinctive trait for the subtribe within the tribe Heliantheae. Analysis of chloroplast DNA from two species of Iostephane, I. heterophylla and I. madrensis, in comparison to Viguiera and related genera indicates that the restriction site patterns with 16 enzymes for the Iostephane species are virtually identical to one another as well as to those of Viguiera sect. Maculatae. Data from restriction fragment patterns of nuclear rDNA are concordant with the results from chloroplast DNA in suggesting a direct relationship between the two groups. The close phylogenetic relationship between Iostephane and Viguiera sect. Maculatae suggested by the DNA restriction fragment data was not suggested by any other set of data.