ORIGINAL ARTICLE Palynological diversity and major evolutionary trends in Cyperaceae Anne Nagels Æ A. Muthama Muasya Æ Suzy Huysmans Æ Alex Vrijdaghs Æ Erik Smets Æ Stefan Vinckier Received: 4 April 2008 / Accepted: 23 September 2008 / Published online: 14 November 2008 Ó Springer-Verlag 2008 Abstract Pollen and orbicule morphology of 84 species, representing 52 genera from all tribes and subfamilies are investigated, in order to assess the systematic value of palynological data and to determine palynological evolu- tionary trends in Cyperaceae. A total of 90% of the species are examined for the first time with scanning electron microscopy. Pollen grains of Cyperaceae are oblate sphe- roidal to perprolate in shape, inaperturate to polyporate with opercula or pontopercula on pori or colpi. We dis- tinguished seven different sexine ornamentation patterns. Orbicules occur in all species investigated. Pollen mor- phological variation within Cyperaceae is considerable and includes dispersal unit; number, location and degree of differentiation of apertural zones; and sexine ornamenta- tion patterns. In subfamily Mapanioideae both tribes can be characterized by palynological synapomorphies. However, in subfamily Cyperoideae, the observed pattern of variation does not fit the most recent molecular phylogeny due to high levels of homoplasy and polymorphism in major pollen characters. Keywords Cyperaceae Á Cyperoideae Á Mapanioideae Á Orbicules Á Palynology Á Pollen Á Pseudomonads Á SEM Introduction Cyperaceae are the third largest family in the monocoty- ledons consisting of 109 genera and approximately 5,500 species (Govaerts et al. 2007). Recent phylogenetic studies based on molecular data have suggested to maintain only two subfamilies within Cyperaceae: Mapanioideae and Cyperoideae (Simpson et al. 2008; Muasya et al. 2008). In this new delimitation Mapanioideae comprise two tribes: Hypolytreae and Chrysitricheae, while the circumscription of Cyperoideae changed considerably to include taxa pre- viously placed in Caricoideae and Sclerioideae (sensu Goetghebeur 1998) (Table 1). The palynology of Cyperaceae attracted quite some attention in the past, mainly because of the occurence of an unusual type of simultaneous microsporogenesis, which leads to the formation of pseudomonads (Selling 1947; Davis 1966) or kryptotetrads (Erdtman 1952). After mei- osis of the microspore mother cell, one of the four nuclei enlarges and occupies the centre of the coenocytic cell, while the other three nuclei migrate to the narrow apex where they are separated by septa and subsequently degenerate (Shah 1962; Dunbar 1973; Strandhede 1973; Furness and Rudall 1999; Brown and Lemmon 2000; Simpson et al. 2003). This unusual pattern of microspo- rogenesis is only known in one other unrelated group: tribe Styphelieae in Ericaceae (Smith-White 1959). A. Nagels (&) Á S. Huysmans Á A. Vrijdaghs Á E. Smets Laboratory of Plant Systematics, Institute of Botany and Microbiology, Kasteelpark Arenberg 31, P.O. Box 2437, 3001 Louvain, Belgium e-mail: annenagels@gmail.com A. M. Muasya Botany Department, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa E. Smets National Herbarium of the Netherlands, Leiden University Branch, P.O. Box 9514, 2300 RA Leiden, The Netherlands S. Vinckier Center for Transgene Technology and Gene Therapy, Flanders Institute for Biotechnology, K.U. Leuven, Campus Gasthuisberg, Herestraat 49, 3000 Louvain, Belgium 123 Plant Syst Evol (2009) 277:117–142 DOI 10.1007/s00606-008-0111-2