Botanic Gardens Trust, Sydney, Australia


Karen Wilson Senior Research Scientist, Adjunct Assoc. Professor (UNE)

The family Cyperaceae is a large cosmopolitan family of 90 genera and 4000 species worldwide, with 50 genera and 650 species (many endemic) in Australia. They are commonly called ‘sedges’.


One of the larger genera is Schoenus, with about 120 species. A few species are spread widely around the world, but the greatest diversity by far is in Australia (about 80 species), particularly in the heathlands of the south-west and south-east of the continent. However, the genus has other species all over Australia, in habitats ranging from tropical to arid and alpine. There is a secondary area of diversity in Malesia (13 species, mostly in higher altitude areas).

Karen Wilson has had a long-standing interest in the genus and has described several new species, including one in the Blue Mountains, Schoenus evansianus, which she named after Mr Obed Evans who had a long career in Botany at the University of Sydney and subsequently was honorary curator of Cyperaceae and other monocots at the National Herbarium of NSW. She did a preliminary survey in the 1990s, funded by ABRS, establishing the value of anatomical characters in distinguishing taxa.

Associate Professor Jeremy Bruhl (University of New England), Mrs Wilson and an ABRS-funded postdoctoral fellow, Dr Adele Gibbs, are examining generic and specific limits in the genus using molecular, morphological, developmental and anatomical methods. Initial results from molecular studies suggest that there are several distinct clades in what has been known as Schoenus. The 'Schoenus team' has been joined by a PhD student at University of New England, Mr Paul Mutuku Musili, who is investigating one major clade in more detail. Mr Russell Barrett (Kings Park and Botanic Garden, Perth) is also contributing molecular data.

This study fits within a broader project involving other cyperologists in South Africa and England, examining the phylogeny of the tribe Schoeneae, which is mainly Gondwanan in distribution but with some taxa extending to northern regions. Preliminary results were presented at the Monocots IV conference held in Copenhagen in August 2008. Further results were aired at the International Botanical Congress in Melbourne in July 2011.

Photosythetic pathways

Grasses (family Poaceae) and sedges are the only two monocot families that include species using the C4 photosynthetic pathway. There are also 16 ‘dicot’ families with C4 species, making this an uncommon condition amongst flowering plants that has evolved multiple times. There are several variants of the C4 pathway occuring in sedges, making the family of particular interest in investigating the evolution of this pathway in flowering plants. Over 500 sedge species in 11 genera use the C4 pathway, with another nine species of Eleocharis being variable or intermediate in their pathways. Some of the most important weedy sedges are C4, such as Cyperus rotundus (Nutgrass).

Typically, the C4 species live in warmer regions, where there is high light, high temperature and good availability of water. These C4 species tend to be cold-sensitive but tolerant of salinity and low nitrogen levels. It is suggested that these species offer an attractive model to investigate the functional significance of C4 photosynthesis in terms of nitrogen-use efficiency, as well as in terms of the traditional, but seemingly inappropriate, hypothesis which relates C4 photosynthesis to water-use efficiency.

Assoc. Prof. Jeremy Bruhl (UNE) and Karen Wilson combined the results of their individual and joint research into the photosynthetic pathways found in all genera of the sedges, plus previously published records, in a major reference paper listing over 3000 observations:  J.J. Bruhl and K.L. Wilson (2007) Towards a comprehensive survey of C3 and C4 photosynthetic pathways in Cyperaceae. Pp. 99-148 in J.T. Columbus et al. (eds.), Monocots: comparative biology and evolution. Published as Aliso 23: 99-148. (Rancho Santa Ana Botanic Garden: Claremont).

Tribe Cariceae

The sedge genus Carex (tribe Cariceae) has about 2100 species, one of the four biggest flowering plant genera worldwide, and the largest plant genus in temperate regions. Species play major ecological roles in many habitats, both as natives and as weeds. Recent research indicates that the generic limits should be broadened to include all genera currently in tribe Cariceae, including Uncinia.

Revisions of such major global taxa provide information essential to species and habitat conservation, ecological restoration, and understanding of biodiversity. With this in mind the International Cariceae Working Group got together in 2011 to compile, vet, and disseminate online information about the many species of Carex, including their taxonomy, images, ecology and biogeography, and identification keys.

The Cariceae group’s first workshop was in September 2011 at the Field Museum in Chicago, funded by the Biodiversity Synthesis Center of the Encyclopedia of Life ( Karen Wilson took part in this workshop, with 30 botanists and computer scientists from Europe, Asia, New Zealand and North America - pictured below Sue, the Field Museum’s prized Tyrannosaurus rex skeleton.

In 2013 a US National Science Foundation grant to revise Carex sens. lat. was awarded to Dr Andrew Hipp (Morton Arboretum, USA), Dr Eric Roalson (Washington State University, USA) and Dr Marcia Waterway (McGill University, Canada), with 14 other members of the Cariceae Working Group from ten countries as collaborators. 

The five-year project will result in:

  • A phylogenetic framework for Carex. Our primary goal is to develop a species-level phylogeny for Carex and identify major lineages that we can use as a framework in revising the sectional classification. Field trips are planned to increase the sampling from about 900 species to about 1360 species in a hierarchical sampling of 3-10 genes, including two DNA barcoding regions already sequenced for hundreds of individuals in this group, to provide a globally useful genetic resource.
  • A revised sectional classification of Carex. A robust phylogeny of the genus is only half of the sectional revision; the other half is identifying lineages and assigning valid names to them. Morphological and DNA data will be used to create a phylogenetically-based infrageneric classification of Carex that is predictive, practical, and robust. This will be the framework for future revisionary, evol-utionary and ecological studies.
  • A database of traits to test diversification patterns and as the basis for predictive classification and monography.
  • A virtual research environment for the Cyperaceae community - see eMonocots The Cyperaceae Scratchpad is being expanded to include character matrix data, DNA sequence data, snapshots of our growing phylogenetic work, climatic and biogeographic data, and taxon descriptions at the species and sectional level. This will create a long-term collaborative platform for generating and publishing data on Carex and other genera.
  • Increased taxonomic capacity, which will help in training the next generation of systematists, increasing taxonomic readiness in pre-college and undergraduate students.






Schoenus species are among the many sedges that grow in the heaths on the Blue Mountains. Photos: Karen Wilson

Even small Schoenus species
supply food to Western Australia's parasitic, yellow-flowered Christmas Tree Nuytsia floribunda. The whitish ball on the Schoenus root is the haustorium through which the Nuytsia draws nutrients.

Cyperus vorsteri
Cyperus vorsteri, a South African C4 species that is becoming a weed in coastal Sydney.

Cyperus cross section
Cross-section of a leaf of Cyperus gunnii, showing the Metcalfe-A variant of C4 anatomy.

Cyperus vorsteri environment
Typical environment for Cyperus vorsteri.

Cariceae group at the Field Museum in Chicago, pictured below Sue, the Field Museum’s prized Tyrannosaurus rex skeleton

Australian alpine and subalpine regions are home to over 20 species of Carex
sens. lat. (view from Charlotte Pass towards Snowy River and Mt Kosciuszko pictured)