The phylogenetic relationships of the Canarian laurel forest endemic Ixanthus viscosus (Aiton) Griseb. (Gentianaceae) are investigated through a cladistic analysis of sequence variation of parts of the chloroplast gene matK and the ITS region of nuclear ribosomal DNA. The floral anatomical and morphological characteristics of Ixanthus based on paraffin sections and SEM studies are also discussed. In the molecular analyses Ixanthus is part of a clade of mostly temperate Erythraeinae and Chironiinae sensu Gilg, in which it is sister to the mostly Mediterranean annual Blackstonia. This relationship is supported by far-reaching similarities in flower morphology and anatomy, and the shared possession of at least some perfoliate leaves. This finding contradicts most former classifications in which Ixanthus was placed either in subtribe Gentianinae which never included Blackstonia, or in a subtribe of its own which was suggested to connect woody tropical with herbaceous temperate taxa. The phylogenetic relationships found here show that 1) the sister group of Ixanthus is distributed in the Mediterranean area, and that 2) its habit as a basally woody suffrutescent herb is best interpreted as an advanced character state.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Plant Science
- Canary Islands
- Floral morphology and anatomy