The evolutionary history of Hypericum (Hypericaceae) with special emphasis on sect. Hypericum - Biogeography, character evolution, ecological shifts, and age estimations

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The genus Hypericum (St. John's wort; Hypericaceae) consists of over 460 species of trees, shrubs and herbs, occurring in temperate regions of the Northern Hemisphere, in tropical high elevation habitats, and with few species, in southern South America (1 sp.) and Australasia (2 spp.). It is one of the 100 largest angiosperm genera and one of the few, if not the only, where the alpha taxonomy is nearly completed due to 50 years of work of Dr. Norman Robson (Natural History Museum, London). Within Hypericum 32 sections are currently recognized. However, no formal cladistic analysis of morphological characters or an extended molecular systematic approach was conducted up to now to circumscribe natural units (i.e. monophyletic groups) of the genus. Within the proposed project a nested phylogenetic analysis approach of Hypehcum will be done. In cooperation with the Natural History Museum a thorough backbone phylogeny of the entire genus will be conducted, analyzing -250 species with nrDNA ITS sequences, a single copy nuclear gene, and a suitable chloroplast DNA region. With this analysis we will test if the sections of Hypericum are monophyletic groups and, if not, circumscribe new monophyletic entities within the genus. For the closer relatives of H. perforatum (Common St. John's wort), i.e. section Hypericum (probably in a new circumscription) and close allies, a detailed analysis of phylogenetic relationships will be done, including several individuals per species, and applying phylogenetic and population genetic analysis methods. For this group nuclear ITS and single copy gene data as well as chloroplast data will be used. On the basis of the phylogenies we will reconstruct character evolution (e.g., herbaceous vs. woody habit, capsules vs. berries, chromosome numbers), historical biogeography (including niche shifts due to changes between tropical and temperate habitats, colonization directions, age of disjunctions), distribution of medically used or usable secondary compounds (hypericin, diuretics), and the evolution of apomixis within Hypericum.