Exploring giant genera and their satellites: tales from the C3 Cyperus universe

Cyperaceae (or sedges) form the third largest plant family of the monocots with ca. 5400 species and 106 genera. Cyperaceae did not only evolve into a large diversity of genera and species in the tropics and subtropics, but they are also often dominantly present in the vegetation of temperate and arctic regions. Sedges contribute significantly to the botanical diversity of wetlands. The Cyperus clade (Cyperoideae, Cypereae) includes ca. 950 species of grass-like plants with complex inflorescences. Species of the Cyperus clade either use C3 photosynthesis (linked with eucyperoid anatomy) (C3 Cyperus), or C4 photosynthesis (linked with chlorocyperoid anatomy) (C4 Cyperus). This PhD project focusses C3 Cyperus. The aim is to create a detailed molecular phylogenetic hypothesis of C3 Cyperus in order to establish (1) how C3 Cyperus relates to C4 Cyperus, and (2) how the different C3 Cyperus taxa relate to one another. In this study, both nuclear ribosomal (ETS1f) and plastid (rpl32-trnL and trnH-psbA) DNA markers are used to create a molecular phylogenetic hypothesis. Molecular phylogenetic data are combined with carbon isotope analysis (D13C), morphology, embryography, floral and spikelet ontogeny, anatomy and biogeography. In our opinion, the Cyperus clade includes two genera Androtrichum and Cyperus (s.l.). C3 Cyperus forms a grade at the basis of Cyperus (C3 photosynthesis is the plesiomorphic state for the Cyperus clade), in which a well-supported monophyletic clade is nested encompassing the C4 Cyperus species. C3 Cyperus (ca. 190 spp.) is less species rich and less diverse than C4 Cyperus (ca. 760 spp.). The small genera Courtoisina and Oxycaryum are included in C3 Cyperus as new sections, which also contain Cyperus s.s. species with intermediate morphologies. The small genus Kyllingiella is included in the existing C3 Cyperus section Leucocephali. These taxa were previously recognised at generic level due to specific characteristics which differentiate them from Cyperus s.s. The currently recognised sections in C3 Cyperus are generally well-supported in the molecular phylogeny, however, ‘Cyperus sect. Glutinosi’ and ‘C. sect. Dichostylis’ sensu Kükenthal are heterogeneous as they include both C3 and C4 species. We aim to provide a revision and a preliminary new classification of C3 Cyperus with clearly characterised monophyletic groups