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RESEARCH PRODUCT

The phylogenetic relationships and evolution of the Canarian laurel forest endemicIxanthus viscosus (Aiton) Griseb. (Gentianaceae): Evidence frommatK and ITS sequences, and floral morphology and anatomy

subject

description

The phylogenetic relationships of the Canarian laurel forest endemicIxanthus viscosus (Aiton) Griseb. (Gentianaceae) are investigated through a cladistic analysis of sequence variation of parts of the chloroplast genematK and the ITS region of nuclear ribosomal DNA. The floral anatomical and morphological characteristics ofIxanthus based on paraffin sections and SEM studies are also discussed. In the molecular analysesIxanthus is part of a clade of mostly temperate Erythraeinae and Chironiinae sensu Gilg, in which it is sister to the mostly Mediterranean annualBlackstonia. This relationship is supported by farreaching similarities in flower morphology and anatomy, and the shared possession of at least some perfoliate leaves. This finding contradicts most former classifications in whichIxanthus was placed either in subtribe Gentianinae which never includedBlackstonia, 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 ofIxanthus 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.