From the Seychelles to Hawaii, and the Caribbean, Australian sedges are expert travellers
You may have heard that 'sedges have edges', but know little more about this fascinating plant family. Sedges are found almost everywhere, except the Antarctic continent. From sea shores to high alpine peaks, they know how to get around.
They also have high species diversity, and many species with very localised distributions. This is particularly true of the Australian Bog Sedges (the genus Schoenus) and their relatives. Ancient Australia appears to be the place of origin for the Bog Sedges, over 55 million years ago.
As Australia came closer to Asia, and volcanic archipelagos rose in the Indian and Pacific Oceans, sedges started to move abroad, starting at least 15 million years ago. Schoenus is best known for a single widespread species, the Black Bog-rush (S. nigricans), named from Europe by Linnaeus. This European history long-overshadowed the Australian origins of the genus, where species diversity is the highest in the world.
Most of the world's sedges are found in wetlands, but Australia has many species that have adapted to dry habitats, including woodland and heath communities. This has given them an edge over other sedge groups when arriving in more arid or seasonal environments.
New research from an international team of sedge researchers has revealed eight major groups (evolutionary lines of descent) within the Bog Sedge tribe Schoeneae. All of these groups are present in Australia, and all eight lineages likely originated there.
Yes, there are specialists in sedges right around the globe - follow @IntSedgeSoc for updates!
The team used the Plant and Fungal Trees of Life (PAFTOL) DNA sequencing protocols, led by the Royal Botanic Gardens Kew, to create the most comprehensive Tree of Life for sedges ever constructed. Sequencing all but four of the 95 sedge genera now recognised globally, the team resolved many relationships that had remained unclear from interpretations of morphology or early DNA studies. [Read the paper for free HERE]
The Bog Sedge tribe has finally been clearly defined, after a rather confusing history, with the removal of a number of genera whose relationships were previously unresolved such as Carpha and Rhynchospora. It now contains 25 genera, just over a quarter of the genera recognised in the whole family.
The first of the eight groups (subtribe Anthelepidinae) has just a single genus, and that only named in 2019. Anthelepis contains just four species, two endemic (restricted) to Australia; one only in New Caledonia; and one ranging across northern Australia and as far north as Hainan (China) and Sri Lanka. This reflects an origin in Australia, with more recent spread to Asia. The four species have a very mixed history of classification as their relationships were difficult to determine based on morphology alone. It was only following the generation of DNA data to illuminate relationships that morphological characters could be identified to characterise the genus.
Photos: Anthelepis paludosa from SE Australia.
Group 2 (subtribe Caustiinae) contains two genera, Caustis and Evandra, and apparently the anomalous species Tetraria borneensis. Caustis is a genus of about 10 species, mostly found in southern Australia, but extending as far north as Rockhampton on the east coast. Evandra contains just two species, both endemic to the south-west of Western Australia. Tetraria borneensis is a poorly known species from lowlands in Borneo and further studies are required to determine its most appropriate classification. It probably represents a dispersal event from southern Australia to Borneo, a disjunction mirrored in a number of plant groups, including Myrtaceae and the sedge genus Lepidosperma.
Photos: Caustis dioica flowers and leaf-like stems, from SW Australia and Caustis flexuosa fruit from SE Australia.
Group 3 (subtribe Gahniinae) contains four genera, Cyathochaeta, Gahnia, Mesomelaena and Ptilothrix. Cyathochaeta has six species in southern Australia. Mesomelaena has five species, all endemic to the south-west of Western Australia, while Ptilothrix has a single species endemic to south-eastern Australia. Gahnia (the Saw Sedges) includes over 40 species, concentrated in southern Australia, but a few species extend across the Pacific to Hawaii, and north to China.
Photos: Gahnia tristis in southern China; Gahnia trifida in SW Australia and Gahnia aspera in SE Australia.
Photos: Mesomelaena tetragona, Mesomelaena pseudostygia and Mesomelaena stygia, all from SW Australia.
Group 4 (subtribe Gymnoschoeninae) includes two distinctive genera Gymnoschoenus (buttongrass) and Reedia. There are two Gymnoschoenus species, one in southern Western Australia and one in south-eastern Australia. Reedia is represented by just a single rare species endemic to the far south-west of Western Australia in permanent swamps surrounded by forest.
Photos: Reedia spathacea and Gymnoschoenus anceps from SW Australia and Gymnoschoenus sphaerocephalus from SE Australia. [Gymnoschoenus photos by @JeremyBruhl]
Group 5 (subtribe Lepidotospermatinae) is the largest subtribe in terms of species, with four genera, Lepidosperma, Machaerina, Neesenbeckia and Netrostylis. Lepidosperma is the largest genus in the tribe, with over 200 species, however many of these are yet to be named, representing the greatest taxonomic gap in our knowledge of Cyperaceae. Lepidosperma has its highest diversity in the south-west of Western Australia, but also has around 50 species in eastern Australia, three in New Zealand, three in New Caledonia, and one ranging from New Guinea to Malaysia and China. Machaerina (including Baumea), includes about 55 species and is the most wide-ranging genus in the tribe. The majority of species are still Australian, but the genus extends though Asia, to Madagascar, and across the Pacific to tropical America, including the Caribbean. Neesenbeckia has just a single species in the Cape region of South Africa. Netrostylis has eleven species (nine of which are soon to be formally named), in southern and eastern Australia, and one species endemic to New Zealand.
Photos: Lepidosperma hopperi (with Steve Hopper for scale), top row; Lepidosperma sp. 'Bluff Knoll Robust'; Lepidosperma sp. 'Erianya Hill' and Lepidosperma oldfieldii, all from SW Australia. [Top left photo by Doc Reynolds]
Group 6 (subtribe Oreoboliinae) includes five genera, each with rather interesting distributions, Capeobolus, Chamaedendron, Costularia, Cyathocoma and Oreobolus. Capeobolus (one species) and Cyathocoma (3 species) are restricted to South Africa. Costularia (15 species) is found in Africa, Madagascar and the West Indian Ocean. Chamaedendron (5 species) is endemic to New Caledonia. Oreobolus (17 species) is the most widespread genus in the subtribe, from Australia to Malesia, New Zealand, Polynesia and Hawaii, and from Costa Rica to the Falkland Islands in South America, and it is mostly found in alpine zones.
Photos: Oreobolus pumilio forms 'cushions' in alpine heath near Mount Kosciuszko, Australia's highest point.
Group 7 (subtribe Schoeninae) includes only the genus Schoenus, with over 150 species. Most of the species are Australian, but there is a secondary radiation in South Africa where most the species were previously included under either Tetraria, or Epischoenus. There are smaller numbers of species in New Zealand, Asia, Europe, the Pacific, and the Americas.
Photos: Schoenus sp. 'White Sheaths', Schoenus calcatus, Schoenus subaphyllus, Schoenus thedae, Schoenus badius (plant and flowers), Schoenus fluitans and Schoenus benthamii.
Group 8 (subtribe Tricostulariinae) includes six genera, Ammothryon, Chaetospora, Morelotia, Tetraria, Tricostularia and Xyroschoenus. Ammothryon, Chaetospora and Tricostularia are all endemic to southern Australia. Morelotia has one species each in Hawaii, French Polynesia and New Zealand, and three species in southwest Western Australia. Tetraria has a disjunct distribution in Southern Africa, Borneo, and New Caledonia, but is now excluded from Australia. Xyroschoenus is endemic to the Seychelles. Tetrariopsis (based on Tetrariopsis octandra) is included under an expanded concept of Morelotia, which also includes Tetraria australiensis and Tetraria microcarpa from south-west Western Australia.
Photos: Ammothryon grandiflorum from SW Australia, Australia's newest and probably last new sedge genus.
Photos: Chaetospora curvifolia from SW Australia, a genus named in 1810, but only recently reinstated to include three southern Australian species.
Future work will focus on the resolution of the many undescribed species remaining in the bog-sedge tribe, in the genera Caustis, Cyathochaeta, Gahnia, Lepidosperma, Machaerina, Morelotia, Netrostylis, Schoenus and Tricostularia.
Recent scientific papers on Cyperaceae tribe Schoeneae [* Open Access]
*Barrett RL. 2013. Ecological importance of sedges: A survey of the Australasian Cyperaceae genus Lepidosperma. Annals of Botany 111: 499–529. https://doi.org/10.1093/aob/mct008
*Barrett RL, Bruhl JJ, Wilson KL. 2021. Netrostylis, a new genus of Australasian Cyperaceae removed from Tetraria. Telopea 24: 53–60. http://dx.doi.org/10.7751/telopea14922
*Barrett RL, Bruhl JJ, Wilson KL. 2021. Revision of generic concepts in Schoeneae subtribe Tricostulariinae (Cyperaceae) with a new Australian genus Ammothryon and new species of Tricostularia. Telopea 24: 61–169. http://dx.doi.org/10.7751/telopea14454
*Barrett RL, Taputuarai R, Meyer J-Y, Bruhl JJ, Wilson KL. 2021. Reassessment of the taxonomic status of Cyperaceae on Rapa Iti, Austral Islands, French Polynesia, with a new combination, Morelotia involuta. Telopea 24: 171–187. http://dx.doi.org/10.7751/telopea14956
Barrett RL, Wilson KL. 2012. A review of the genus Lepidosperma Labill. (Cyperaceae: Schoeneae). Australian Systematic Botany 25: 225–294. https://doi.org/10.1071/SB11037
Barrett RL, Wilson KL, Bruhl JJ. 2019. Anthelepis, a new genus for four mainly tropical species of Cyperaceae from Australia, New Caledonia and South East Asia. Australian Systematic Botany 32(4): 269–289. https://doi.org/10.1071/SB18047
*Barrett RL, Wilson KL, Bruhl JJ. 2020. Reinstatement and revision of the genus Chaetospora (Cyperaceae: Schoeneae). Telopea 23: 95–112. http://dx.doi.org/10.7751/telopea14345
Elliott TL, Barrett RL, Muasya AM 2019. A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae)––Part 1. South African Journal of Botany 121: 519–535. https://doi.org/10.1016/j.sajb.2018.11.021
Elliott TL, Muasya AM. 2018. A taxonomic revision of Schoenus compar – Schoenus pictus and allies (Cyperaceae, tribe Schoeneae) with three new species described from South Africa. South African Journal of Botany 114: 303–315. https://doi.org/10.1016/j.sajb.2017.11.020
Elliott TL, Muasya AM. 2020. A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae)—Part 2. South African Journal of Botany 130: 327–347. https://doi.org/10.1016/j.sajb.2019.12.015
Elliott TL, Muasya AM. 2020. A taxonomic revision of the Epischoenus group of Schoenus (Cyperaceae, tribe Schoeneae). South African Journal of Botany 135: 296-316. https://doi.org/10.1016/j.sajb.2020.08.029
*Elliott TL, van Mazijk R, Barrett RL, Bruhl JJ, Joly S, Muthaphuli N, Wilson KL, Muasya AM. 2021. Global dispersal and diversification of the genus Schoenus (Cyperaceae) from the Western Australian biodiversity hotspot. Special Issue: Cyperaceae in a data-rich era: New evolutionary insights from solid frameworks. Journal of Systematics and Evolution 59(4): 791–808. https://doi.org/10.1111/jse.12742
*Larridon I, Rabarivola L, Xanthos M, Muasya AM. 2019. Revision of the Afro‐Madagascan genus Costularia (Cyperaceae): Infrageneric relationships and species delimitation. PeerJ 7: e6528 https://doi.org/10.7717/peerj.6528
Larridon I, Semmouri I, Bauters K, Viljoen JA, Prychid CJ, Muasya AM, Bruhl JJ, Wilson KL, Goetghebeur P. 2018. Molecular phylogenetics of the genus Costularia (Schoeneae, Cyperaceae) reveals multiple distinct evolutionary lineages. Molecular Phylogenetics and Evolution 126: 196–209. https://doi.org/10.1016/j.ympev.2018.04.016
Larridon I, Verboom GA, Muasya AM. 2017. (2555) Proposal to conserve the name Tetraria (Cyperaceae) with a conserved type. Taxon 66: 1226–1227. https://doi.org/10.12705/665.22
Larridon I, Verboom GA, Muasya AM. 2018. Revised delimitation of the genus Tetraria, nom. cons. prop. (Cyperaceae, tribe Schoeneae, Tricostularia clade). South African Journal of Botany 118: 18–22. https://doi.org/10.1016/j.sajb.2018.06.007
*Larridon I, Zuntini AR, Léveillé-Bourret E, Barrett RL, Starr JR, Muasya AM, Villaverde T, Bauters K, Brewer GE, Bruhl JJ, Costa SM, Elliott TL, Epitawalage N, Escudero M, Fairlie I, Goetghebeur P, Hipp AL, Jiménez-Mejías P, Sabino Kikuchi IAB, Luceño M, Márquez-Corro JI, Martín-Bravo S, Maurin O, Pokorny L, Roalson EH, Semmouri I, Simpson DA, Spalink D, Thomas WW, Wilson KL, Xanthos M, Forest F, Baker WJ. 2021. A new classification of Cyperaceae (Poales) supported by phylogenomic data. Special Issue: Cyperaceae in a data-rich era: New evolutionary insights from solid frameworks. Journal of Systematics and Evolution 59(4): 852–895. https://doi.org/10.1111/jse.12757
Musili PM, Gibbs AK, Wilson KL, Bruhl JJ. 2016. Schoenus (Cyperaceae) is not monophyletic based on ITS nrDNA sequence data. Australian Systematic Botany 29: 265–283. https://doi.org/10.1071/SB15046
Verboom GA. 2006. A phylogeny of the schoenoid sedges (Cyperaceae: Schoeneae) based on plastid DNA sequences, with special reference to the genera found in Africa. Molecular Phylogenetics Evolution 38: 79–89. https://doi.org/10.1016/j.ympev.2005.05.012
Viljoen J-A, Muasya AM, Barrett RL, Bruhl JJ, Gibbs AK, Slingsby JA, Wilson KL, Verboom GA. 2013. Radiation and repeated transoceanic dispersal of Schoeneae (Cyperaceae) through the southern hemisphere. American Journal of Botany 100: 2494–2508. https://doi.org/10.3732/ajb.1300105