The changing taxonomy of Schoenus
Before I came to Cape Town several years ago for my postdoctoral studies, little was known about Schoenus in southern Africa. In fact, the cosmopolitan Schoenus nigricans was the only known species of the genus in the region. However, Tetraria, a genus of closely related sedges, was well-documented in southern Africa.
The transfer of species from Epischoenus & Tetraria to Schoenus
My first endeavour was to split the southern African Schoenus from Tetraria and Epischoenus. Previous molecular analyses showed that the genus Tetraria consisted of species that were distantly related, and that some of these were more closely related to Schoenus species than to the other southern African Tetraria. Furthermore, almost all Epischoenus species were found to be closely related to Schoenus. Based on these new insights, Muthama Muasya and myself transferred 24 species of Epischoenus and Tetraria into an expanded Schoenus. Our work was featured in the following publication:
Taxonomic realignment in the southern African Tetraria (Cyperaceae, tribe Schoeneae; Schoenus clade): doi:10.1016/j.sajb.2017.06.011
Three extensive taxonomic revisions of the southern African Schoenus
Our work had only started. Now it was time to jump into the details!
We started by revising two of the most conspicuous of the southern African Schoenus, which are Schoenus compar and Schoenus pictus. Based on the previous analyses, we knew that these two species were closely-related. We also had fairly strong evidence that there were other similar species in this group that were fairly widespread, such as what is now Schoenus arenicola and Schoenus pseudoloreus. This first revision also included the description of three new species to science: Schoenus aureus, Schoenus megacarpus and Schoenus filiculmis. Interestingly, species in this group sometimes have a sticky substance on their stem bases or flowering heads.
A taxonomic revision of Schoenus compar - Schoenus pictus and allies (Cyperaceae, tribe Schoeneae) with three new species described from South Africa: doi:10.1016/j.sajb.2017.11.020
The next step was revising the difficult and confusing Schoenus cuspidatus group. The differences among species in this group are slight and many had been lumped as S. cuspidatus in the past. When one looks at these species in the field and examines specimens, there are slight differences between species. Moreover, it is common for species in this group to co-occur, but in slightly different microhabitats.
For the most part, many of the species in the S. cuspidatus group have a similar form of flower, but with small differences. Visible differences also exist in the bases of the plants and in the fruits.
We decided to divide this revision in two parts because of the size of the group and the difficulties in handling the taxonomy:
A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae)—Part 1: doi:10.1016/j.sajb.2018.11.021
A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae)—Part 2: doi:10.1016/j.sajb.2019.12.015
The remaining taxonomy to tackle was that of the species formerly in the genus Epischoenus. These species tend to be leafless and prefer more damp habitats compared to the other southern African Schoenus. The revision of this group included 11 species, including three new to science: Schoenus crinitus, Schoenus rigidus and Schoenus selinae.
A taxonomic revision of the Epischoenus group of Schoenus (Cyperaceae, tribe Schoeneae): 10.1016/j.sajb.2020.08.029
The papers mentioned above were all published in South African Journal of Botany.
Even more new species
After our preparation of the respective taxonomic revisions, we discovered several other species that had not yet been described. Furthermore, we transferred one species to the rank of species which had previously been a variety of Tetraria. Some of these species are closely-related to S. compar and S. pictus (Schoenus albovaginatus, Schoenus comparoides and Schoenus triticoides), while others fit in more with the S. cuspidatus group (Schoenus inconspicuus). We are still not sure which group Schoenus bracteosus fits in with, as it might be from hybrid origin.
Muthama and I published the first paper describing new species in Phytotaxa:
Three new species and a new combination among Southern African Schoenus (Cyperaceae, tribe Schoeneae): 10.11646/phytotaxa.401.4.4
We recently described a new species with the help of Doug Euston-Brown, also in Phytotaxa. Doug brought us an important specimen at a critical time and helped with the writing of the paper:
Schoenus inconspicuus (Cyperaceae, tribe Schoeneae): a new species from Southern Africa: 10.11646/phytotaxa.440.3.6
Still more new species to be described
The cabinets of the Bolus herbarium contain two new species yet to be described. Further evidence is still needed before we describe them. That being said, we would love to have new specimens of them.
I am also confident that there are several other new species out there, waiting for others (such as you) to find them. I have looked at thousands of specimens over the last several years and there are lots of things that just look odd and don't fall in with any of the previously described species.
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The two new undescribed species:
where are they recorded from?
how do we know when we have found them: any interesting or distinctive features to look for?
The first potential species has been collected from the slopes around Kogelberg, Palmiet River, Rooi Els and Kleinmond. It is short (most likely < 300 mm in height) with short spikelets (< 4mm if I recall correctly). It is about a year since I last saw the specimens, but I think that the spikelets had a slight twist or other abnormality to them, which differentiates them from Schoenus exilis. This species had been labelled Tetraria scariosa in the herbarium cabinets, although I am not sure if that name was ever officially published.
The second potential species is from the Drakensberg area, with specimens collected from over 5000 feet in the Ndedema area and the Cathedral Peak Forest Reserve Station. Specifically, the one specimen was collected from a ' moist floor of cave in Mhlwasine River Valley'. If I remember correctly, the spikelets are scattered throughout diffuse panicles, somewhat like some specimens of Schoenus gracillimus. As I have not looked at the specimens in nearly a year, I can't remember anything else. Importantly, we have not seen any other specimens of Schoenus from the Epischoenus group in that region.
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