The genus Cyperus s.l. (950 species) is one of the largest genera in the Cyperaceae. The most obvious diagnostic characteristic is the presence of spikelets with distichous glumes. As is the case for many giant genera, the taxonomic relationships in Cyperus s.l. are still for a large part unclear. However, within Cyperus s.l. several groups can be distinguished morphologically. Many of these groups were placed in separate (sub)genera. According to the first phylogenetic analyses based on markers from the chloroplast genome these groups are nevertheless nested in Cyperus s.s.

Globally seen, the genus Cyperus falls apart in two groups, namely the C3 group and the C4 clade. Each group is characterised by its own photosynthesis type, which is linked to the anatomy type.

The C4 clade is by far the largest and most diverse (60 sections (including those of Pycreus and Kyllinga) and (sub)genera in contrast to the C3 group with 10 sections and (sub)genera). To the strongly evolved branches of the C4 clade belong, amongst others, Pycreus (approximately 120 species), Kyllinga (approximately 73 species) and Queenslandiella (1 species). Besides Pycreus and Kyllinga other satellite genera are nested in the C4 clade such as Lipocarpha (36 species), Ascolepis (22 species) and a number of monospecific genera.

The remarkable, laterally compressed pistils, composed of only two ‘carpels’ are the most important diagnostic characters for the genus Pycreus (Cyperaceae). The origin of this requested complete new gynoecial architecture, with new vascular patterns. Also two other genera, Kyllinga and Queenslandiella, both related to Cyperus, have a comparable architecture and placement of the gynoecium, of which the anatomical structure is still unclear. Did the laterally compressed pistils of these two genera originated in the same "unique" evolutionary event? This homology problem will be studied with 3D computer reconstructions from slices trough the nutlets of these genera, to reveal the evolutionary patterns. Besides this we will make an ontological study of the youngest stages in flower and spikelet architecture in cooperation with Alexander Vrijdaghs (KULeuven).

A next step will be a phylogenetic reconstruction of these genera with nucleus and chloroplast genomic sequences. This study will be done in cooperation with the Royal Botanical Gardens, Kew. Research has revealed that the genus Cyperus is composed of at least two different clades, and that the relationship with Kyllinga, Pycreus and Queenslandiella can exclusively been found in the C4 clade. This study will show if the genera are monophyletic and what’s the relationship with the C4 species of Cyperus. Besides this the intrageneric taxonomy of both Pycreus and Kyllinga is poorly known, this genetic study will certainly give more insights.

Finally, world revisions of the three genera are suggested. We will work with a database accessible from the Internet, with descriptions, pictures, genomic sequences, literature, maps and interactive keys.

Marc Reynders (Pycreus)
Wim Huygh (Kyllinga)