An integrative monograph of Carex section Schoenoxiphium (Cyperaceae)

Carex section Schoenoxiphium (Cariceae, Cyperaceae) is endemic to the Afrotropical biogeographic region and is mainly distributed in southern and eastern Africa, with its center of diversity in eastern South Africa. The taxon was formerly recognized as a distinct genus and has a long history of taxonomic controversy. It has also an important morphological and molecular background in particular dealing with the complexity of its inflorescence and the phylogenetic relationships of its species. We here present a fully updated and integrative monograph of Carex section Schoenoxiphium based on morphological, molecular and cytogenetic data. A total of 1,017 herbarium specimens were examined and the majority of the species were studied in the field. Previous molecular phylogenies based on Sanger-sequencing of four nuclear and plastid DNA regions and RAD-seq were expanded. For the first time, chromosome numbers were obtained, with cytogenetic counts on 44 populations from 15 species and one hybrid. Our taxonomic treatment recognizes 21 species, one of them herein newly described (C. gordon-grayae). Our results agree with previous molecular works that have found five main lineages in Schoenoxiphium. We provide detailed morphological descriptions, distribution maps and analytical drawings of all accepted species in section Schoenoxiphium, an identification key, and a thorough nomenclatural survey including 19 new typifications and one nomen novum.


INTRODUCTION
. Carex has a nearly cosmopolitan distribution, with higher species richness in cold-temperate regions of the Northern Hemisphere and lower species numbers in the Southern Hemisphere, especially at tropical latitudes. In particular, the Afrotropical biogeographic realm is the poorest one in terms of Carex species, with 111 species (Martín-Bravo et al., 2019). Nonetheless, important hotspots of Carex diversity and endemicity are found in southern Africa and Madagascar, which harbour the highest number of species in Sub-Saharan Africa (Govaerts et al., 2020;Larridon et al., 2021). An important proportion of South African's Carex diversity corresponds to section Schoenoxiphium (Nees) Baillon, which is considered one of the few examples of an in-situ radiation of the genus in the Afrotropical region (Martín-Bravo et al., 2019;.
Previous molecular phylogenies focused on section Schoenoxiphium were based on a relatively small number of DNA regions (nuclear ITS and ETS; plastid trnL-F, matK and rps16). They found a well-supported internal phylogenetic backbone composed of five strongly supported main clades (Clades A-E; Gehrke et al., 2010;Villaverde et al., 2017;, although species relationships remained partially unresolved, sometimes suggesting the existence of cryptic species, which have been recently described this study). Furthermore, the available phylogenetic evidence suggests a complex evolutionary history, as illustrated by a documented case of intersectional hybridization followed by recombination involving section Schoenoxiphium (Clade E) and another member of subgenus Psyllophorae (C. camptoglochin V.I.Krecz., section Junciformes) (Gehrke et al., 2010). Molecular phylogenies have also revealed that C. acocksii C. Archer, a poorly known unispicate species with remarkable morphological, molecular, biogeographical and ecological differentiation, unexpectedly belongs to the section Schoenoxiphium . More recently, a phylogenomic approach based on RAD-seq has further helped to clarify the systematics of section Schoenoxiphium .
In addition, while the five main lineages detected by previous phylogenies are wellsupported, there are no clear combinations of morphological synapomorphies characterizing them. Moreover, weak morphological boundaries and species non-monophyly are common patterns found within some lineages (e.g. Clades C, D and E; Villaverde et al., 2017). High phenotypic plasticity has also been suggested to be related with these delimitation problems . Thus, conspicuous morphological differences (e.g. in organ size or inflorescence complexity) have been observed between populations of the same species growing at different altitudes (e.g. C. killickii Nelmes).

Biogeographic and evolutionary patterns
Section Schoenoxiphium is endemic to the Afrotropical biogeographic region, with a clear center of diversity in eastern South Africa. It is distributed in southern and eastern Africa, including Madagascar, and marginally reaches the mountains of SE Arabian Peninsula . Interestingly, the high species number of the section in South Africa makes this one of the few regions worldwide where the richest Carex group is not the large subgenus Carex, but another one, in this case subgenus Psyllophorae.
The diversification of section Schoenoxiphium has been dated back to the Middle to Late Miocene (c. 8-16 mya;Martín-Bravo et al., 2019;Villaverde et al., 2021), with its ancestral area probably located in the Drakensberg range in E South Africa, and several subsequent colonizations out of this area have been inferred, including the Cape region, tropical E Africa and Madagascar . Active speciation processes in the Drakensberg could have taken place in concert with the uplift of this range during the Mio-Pliocene boundary (5.5 mya; . The weak morphological boundaries, species lack of monophyly, together with the often overlapping distribution of species within lineages ; see maps in Taxonomic treatment) and their frequent turnover along various ecological gradients (elevation, wetness, forest to grassland; see habitat description under each species) suggest that ecological specialization may have played an important role in the diversification of some main lineages within section Schoenoxiphium, perhaps linked to geomorphological evolution in the region (Bentley, Verboom & Bergh, 2014).
Sedges (Cyperaceae) present several uncommon cytological characteristics among angiosperms: (i) degeneration of three nuclei during pollen formation (pseudomonads), (ii) postreductional meiosis with separation of chromosomes in anaphase II instead of anaphase I (inverted meiosis), and (iii) extended kinetochoric activity during cell division (holocentric/holokinetic chromosomes). These peculiarities allow a more relaxed chromosome number inheritance, as fragments from fission events are very likely to carry functional centromeres, and fused chromosomes would not have division problems due to inverted meiosis (Mola & Papeschi, 2006;Hipp, Escudero & Chung, 2013;Márquez-Corro et al., 2019a). Chromosome number evolution in Carex is dominated by dysploid events-even within species-, with exception of the polyploid early-diverging subgenus Siderosticta Waterway and other minor sparse lineages (Roalson, 2008;Hipp, Rothrock & Roalson, 2009;Escudero et al., 2012). Some species present large dysploid series (Luceño & Castroviejo, 1991;Hipp et al., 2010). The fact of dealing with extremely variable, wide chromosome number ranges even within species has historically hindered the estimation of ancestral numbers for the genus (Wahl, 1940;Roalson, 2008), even with recent evolutionary analyses (Escudero et al., 2014;Márquez-Corro et al., 2019b. No cytological study has ever been carried out in Carex section Schoenoxiphium. This lack of karyological knowledge has motivated its study during the last few years. Although some of these chromosome counts have been previously used for evolutionary works at different levels (Luceño et al., 2013;Márquez-Corro et al., 2019b;Márquez-Corro et al., 2021), these chromosome counts are formally published here for the first time.
The inflorescence of the species in the section Schoenoxiphium has often been discussed in these studies due to its particularities (Kukkonen, 1983(Kukkonen, , 1994Timonen, 1998;Global Carex Group, 2015;Jiménez-Mejías et al., 2016). In short, the inflorescences of the species in the section vary from very simple, reduced to an androgynous spike at the end of the fertile stem, as is the case of C. acocksii and certain morphotypes of C. killickii , to complex, constituting paniculiform inflorescences whose density and branching pattern is variable (Fig. 1).
Inflorescences of the species in the section Schoenoxiphium show 1-4 branching orders (Fig. 1). The shape of the last order branches (rachilla) is very typical of the species in the section: straight, flat, linear to lanceolate in outline, with one central vein and ciliated or scabrous at the margins. Complex inflorescences are composed of a variable number of spiciform or paniculiform partial inflorescences (paracladia). Frequently, the lower partial inflorescences are variably pedunculated, usually distant and sometimes nodding, while the upper ones are usually sessile or subsessile and usually appear congested in the upper part of the inflorescence, which makes their individualization quite difficult. Each partial inflorescence is subtended by a leaf-like bract (more rarely, glumaceous, setaceous or intermediate between the latter two types) and surrounded at its base by an usually tube-shaped prophyll called tubular cladoprophyll (Jiménez-Mejías et al., 2016). The type of prophyll in the section Schoenoxiphium depends on the order of branching, so that, except in unispicate inflorescences, the cladoprophyll of the first-order branches is tubular ( Fig. 1) and usually hyaline, while those of the following branching orders are utriculiform cladoprophylls (Fig. 2C), bisexual or unisexual utricles (Figs. 2A,2B) or, more rarely (C. lancea, C. multispiculata and C. schweickerdtii), open perigynia (Figs. 2D-2F). However, the morphology of each type of cladoprophyll is not always homogeneous, so that tubular cladoprophylls may vary from strictly tubular to hypocrateriform, symmetric or asymmetric in the apical opening (mouth); likewise, the utriculiform cladoprophylls also vary notably in shape, although those that resemble bisexual utricles predominate, and are distinguishable from unisexual utricles by their broad and obliquely truncated mouth. It is worth noting the extraordinary morphological variability of prophylls, encompassing all imaginable intermediate forms between unisexual utricles and open perigynia (see Materials and Methods for a detailed explanation of prophyll types and the terminology adopted here; Fig. 2).
To summarize, there is a plethora of useful but fragmentary data that have contributed to improve our knowledge on the systematics, biogeography and evolution of section Schoenoxiphium. Thus, during the last 13 years, the authors of this study have been studying these aspects, which has resulted in several publications specifically focused on this group (Gehrke et al., 2010;Villaverde et al., 2017Villaverde et al., , 2021Márquez-Corro et al., 2017Márquez-Corro et al., 2021). It is particularly noteworthy how the increasing efforts in taxonomic and molecular sampling have enabled a much more robust and sound phylogenetic inference for section Schoenoxiphium. This has been possible thanks to the progressive development of sequencing methods (from a few Sanger-sequenced DNA regions to the massive parallel sequencing of hundreds or thousands of loci with genomic techniques like Hyb-Seq or RAD-seq). However, a critical taxonomic revision that accounts for this phylogenetic framework is still lacking. Therefore, we herein present a fully updated and integrative global monograph of the group that includes the study of more than 1,000 herbarium specimens and considers all available sources of evidence.

Morphological study
We have studied 1,017 vouchers of type and representative material (Table S1 in Supplementary Material) from the following herbaria (codes following Thiers, 2020), through in situ visits, the request of material on loan or digitized images of herbarium specimens, and the study of specimens available in the online repository JSTOR Global  BM, BOL, E, EA, GRA, K, MA, MO, NBG, NU, P, PRE, S,  SALA, SBT, TCD, TUB,  Herbarium material was identified and studied taking into account all relevant previous taxonomic literature, and with a special focus on the most important characters for the taxonomy of section Schoenoxiphium (Kükenthal, 1909;Levyns, 1945;Kukkonen, 1983;Gordon-Gray, 1995;Márquez-Corro et al., 2017; this study): width and length of rhizome internodes; lower sheath leaves bladeless or with lamina, decaying or not in fibres; width and cross section of the leaves; presence-absence of papilles and/or pricklets in leaf margins; ligule length; lowest inflorescence bract sheathing or not; inflorescence structure; length of partial inflorescences peduncles; presence-absence of open perigynia and utriculiform cladoprophylls; shape, size and indumentum of unisexual utricles; relative length of the rachilla with respect to the utricle; shape and size of the achenes; and shape of persistent style base. Macroscopic measurements were performed using a standard ruler. An Olympus SZX16 binocular magnifying glass was used to measure culm-width, leafwidth, ligules, glumes, achenes and utricles.
Regarding the terminology used in the key and in the descriptions, we basically follow the guidelines set out by Global Carex Group (2015) and Jiménez-Mejías et al. (2016), with minor modifications. We consider rhizome "slender" when its diameter does not exceed 3 mm, "moderately stout" when the diameter ranges between 3 and 6 mm and "stout" when exceeding 6 mm in diameter. We consider that the lowest bract of the inflorescence is not sheathing when the sheath is open or closed up to 7 mm above the insertion of the bract on the culm. The basal sheaths characters are referred only to those of fertile culms. Features and dimensions of the utricle always refer to mature unisexual utricles; in the same way, the shape and dimensions of the female glumes refer exclusively to those axilating the unisexual utricles, not the bisexual ones or to the utriculiform cladoprophylls. On the contrary, achenes have been described considering those included in utriculiform cladoprophylls, in glumiform perigynia, in glumiform cladoprophylles (see below) and in unisexual and bisexual utricles, since no variation was observed. We have considered partial inflorescence (first order paracladium; Guarise & Vegetti, 2008) as the branch that arises directly from the main axis and branches at least twice ( Fig. 1). Regarding prophylls, Jiménez-Mejías et al. (2016) consider two types: (i) perigynium as any prophyll enclosing a female flower and surrounding the base of a terminal truncated short branch, and (ii) cladoprophyll as any modified prophyll surrounding lower order branches. When the margins of perigynia are fused, constituting a more or less closed structure, we distinguish two types of perigynia: (i) bisexual utricle (Fig. 2B), which encloses an achene and whose axis projects, outside the cladoprophyll, into a male spikelet; and (ii) unisexual utricle ( Fig. 2A), when the axis is vestigial or protrudes from the apex of the cladoprophyll, but does not elongate into new branches that carry flowers nor a male spikelet, at most the branches carry some vestigial scales (glumes) at the apex. In addition, when the margins of cladoprophylls are fused, Jiménez-Mejías et al. (2016) also accept two types: (i) tubular cladoprophyll (Fig. 1), when it does not enclose a female flower; and (ii) utriculiform cladoprophyll (Fig. 2C), if they contain an achene and the axis of the branch protrudes from the apex of the cladoprophyll, generating new branches that produce female flowers and end in a male spike. Since the species of the section Schoenoxiphium show a great variability in the shape and position of the different types of prophylls, we accept here the classification proposed by Jiménez-Mejías et al. (2016), but we will additionally refer to glumiform perigynia, as those last-order branch prophylls whose edges are not fused or only very shortly in the base (Figs. 2D, 2E), similar to those of the species of the former genus Kobresia and those observed in C. lancea (Thunb.) Baill., C. multispiculata Luceño & Martín-Bravo, and C. schweickerdtii (Merxm. & Podlech) Luceño & Martín-Bravo, and to glumiform cladoprophylls as the open or shortly fused in the base prophylls that contain an achene and whose branch axis protrudes from the apex of the cladoprophyll, generating new branches that produce female flowers and end in a male spike (Fig. 2F).
The distribution of taxa was specified using TDWG geographical codes at level 3 ("Botanical countries"; Brummitt, 2001), and represented in maps using the program QGis (https//qgis.org). Herbarium specimens without exact coordinates were manually georeferenced when the locality was clear and precise, in order to represent species distributions as complete as possible. Habitats description was based on field observations as well as on the classification of South African vegetation by Mucina & Rutherford (2006). Analytical drawings were prepared for all accepted species by M. Sánchez-Villegas, except for C. badilloi Luceño & Márq.-Corro, C. bolusii C.B.Clarke (prepared by R. Tavera) and C. chermezonii Luceño & Martín-Bravo (only known from the type material), including details of the most important diagnostic characters of inflorescences, utricles and achenes. Representative iconography and selected references relevant for each accepted species were cited. The conservation status of species was reviewed and mainly obtained at the national level for South Africa (Red List of South African Plants; SANBI, 2020) and only for one species at the global level (Carex ludwigii;IUCN, 2020).

Molecular study
We included new samples in the previous molecular phylogenies of section Schoenoxiphium based on Sanger-sequencing of DNA regions  ten new samples, representing six species, with all four regions each; see Table S2 in Supplementary Material) and RAD-seq  2 new samples representing two species). Thus, we expanded the taxon sampling, including one herein newly described species previously unsampled (C. gordon-grayae Luceño, Márq.-Corro & Sánchez-Villegas sp. nov.) and one species recently included in the section (C. acocksii; . Methods for DNA extraction, PCR amplification and phylogenetic analysis were similar to the ones used in the respective Sanger and RAD-seq studies . For the RAD-seq assembly, we used iPyrad v.0.9.59 (Eaton & Overcast, 2020). Maximum likelihood (ML) trees, using the concatenated individual marker matrices and the concatenated RAD-seq matrix, independently, were inferred in RAxML 7.2.6 (Stamatakis, 2014) and bootstrap support for clades were calculated using 200 non-parametric replicates searches from random starting trees using an unpartitioned GTR+CAT nucleotide substitution model.

Cytogenetic study
Cytogenetic preparations were performed through the fixation of developing pollen grains from immature anthers, following the standard protocol for Carex described in Luceño (1988) and Escudero et al. (2008). Diploid numbers were inferred from obtained meiotic plates in Diakinesis (DK), Metaphase I (MI) or Metaphase II (MII) of the meiosis, as well as in Pollen Grain Mitosis (PGM), more rarely in premeiotic mitosis.

Nomenclature
The electronic version of this article in Portable Document Format (PDF) will represent a published work according to the International Code of Nomenclature for algae, fungi, and plants (ICN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. In addition, new names contained in this work which have been issued with identifiers by IPNI will eventually be made available to the Global Names Index. The IPNI LSIDs can be resolved and the associated information viewed through any standard web browser by appending the LSID contained in this publication to the prefix "http://ipni.org/". The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central, and CLOCKSS.

Taxonomic revision
Our taxonomic treatment considers 21 accepted species, one of them newly described here (C. gordon-grayae sp. nov.). Detailed morphological descriptions, distribution maps and analytical drawings are provided for all of them, as well as a general description for section Schoenoxiphium. An identification key is provided to distinguish between all species. A total of 19 new formal typifications and one nomen novum are provided. Our exhaustive revision of materials also revealed that section Schoenoxiphium is distributed in 13 countries through southern and eastern Africa, with an interesting disjunction in West Africa (C. dregeana in W of Angola) and a population of C. spartea in the Republic of Yemen (Arabian Peninsula, Asia; Al-Khulaidi, 2013), whose voucher we have not been able to confirm, although we consider its presence plausible. South Africa has the highest number of species (20 out of 21), followed by Lesotho (11). Within South Africa, the provinces with the greatest species richness are the Eastern Cape with 17 species and KwaZulu-Natal with 15 (Fig. 3).
The monophyly of Carex section Schoenoxiphium is strongly supported using both Sanger and RAD-seq datasets (97% and 100% BS, respectively; Fig. 4 and Figs. S1, S2). Most of the main lineages are strongly supported in both phylogenetic reconstructions, with the exception of Clade A. The relationships between all these clades are weakly supported in the phylogenetic reconstruction using four different DNA regions (Fig. 4A), but they are strongly supported using the genomic RAD-seq dataset (Fig. 4B). Carex ackocsii appears in a weakly supported lineage sister to Clade D, while C. gordon-grayae in an unresolved lineage (Fig. 4A). Carex sciocapensis is retrieved as paraphyletic (Figs. 4A, 4B). Summary statistics for the individual marker matrices obtained with AMAS (Borowiec, 2016) are found in Table S3. Summary statistics for the RAD assembly are found in Table S4 in Supplementary Material.

Chromosome numbers and meiotic configurations
We report new chromosome numbers for 15 species (two thirds of the section) and one putative (morphologically intermediate) hybrid in Table 2, Figs. 4 and 5. The counts show a distribution around three chromosome number clusters (see also Márquez-Corro et al., 2021): 2n = 24-36, 2n = 60-72 and a single count of 2n = 88 (Fig. 5). We also indicate the meiotic configuration, which may be different for the same chromosome number, due to the presence of univalents, bivalents or trivalents.

DISCUSSION
We have produced a fully updated and integrative study of Carex section Schoenoxiphium based on 1,017 herbarium specimens, field works conducted between 2008-2017, 164  sequenced samples represented in a Sanger and a RAD-seq phylogeny, cytogenetic counts on 44 populations, a nomenclatural survey and an exhaustive review of previous taxonomic and phylogenetic works. Our taxonomic treatment considers 21 accepted species (Table 3), one of them newly described here (C. gordon-grayae sp. nov.). We provide detailed morphological descriptions, distribution maps, analytical drawings and an identification key including all species, as well as a general description for section Schoenoxiphium. A total of 19 new formal typifications and one nomen novum are provided.

Systematics of Schoenoxiphium
Carex section Schoenoxiphium consists of five well-supported evolutionary lineages: (A) C. schweickerdtii, C. lancea and C. multispiculata; (B) C. burkei, C. basutorum, C. distincta and C. killickii; (C) C. capensis and C. sciocapensis; (D) C. acocksii, C. perdensa, C. dregeana, C. esenbeckiana and C. spartea; (E) C. pseudorufa, C. ludwigii, C. kukkoneniana, C. badilloi and C. bolusii. Although Clade A is retrieved in a weakly supported lineage (Fig. 4), it has been shown to be strongly supported in Márquez-Corro    (2020). Similar situation occurs with C. acocksii, which is found in a moderately supported lineage in  but it lacks of support here. Carex gordon-grayae sp. nov. and C. chermezonii (the later not included in any molecular analysis to date) are the only two species whose phylogenetic relationships have not been resolved yet. However, their morphological characteristics led us to hypothesize that C. chermezonii would belong to Clade A, and C. gordon-grayae to an isolated lineage. Section Schoenoxiphium probably originated in the Mid-Miocene in the Afrotropical region and diversified in-situ (mean c. 8-16 mya; Martín-Bravo et al., 2019;Villaverde et al., 2021), probably in the Drakensberg and adjacent mountain ranges . Most of the species in Schoenoxiphium are suspected to have originated during the Late Miocene , which corresponds to the uplift of the Drakensberg Mountains, the only South Africa's alpine zones. The provinces of Eastern Cape and KwaZulu-Natal treasure the highest number of section Schoenoxiphium species in South Africa (17 and 15, respectively; Fig. 3) followed by the country of Lesotho (11 species).
This small clade of three species (or perhaps four; our untested hypothesis is that C. chermezonii belongs to this clade) is formed by large plants with wide leaves and straight apex leaves (but usually somewhat curved in C. lancea). Unlike other species in the section, these species may have open perigynia (occasional in C. multispiculata; not seen in C. chermezonii). Utricles are smooth, linear and gradually attenuated into a smooth beak; usually of medium size (4.4-6.5 mm), but C. schweickerdtii may display among the largest utricles in the section (6-10 mm). Species in this clade are mainly distributed in southern Africa; additionally, C. schweickerdtii is also found in Zimbabwe, C. multispiculata in Madagascar, and C. chermezonii has only been found in its type locality in the Tsaratanana mountains of Madagascar. They usually occur in edges of streams or damp places in medium-high mountains (C. schweickerdtii also in stony meadows), although C. lancea is found in forests at low elevations (20-1,500 m).
Species in this clade are characterized by plants of small height, with very narrow or filiform leaves (0.2-3.7 mm, but C. burkei has wider ones, 1.5-5.5 mm) curved to curled at the tip. Utricles are linear or narrowly ellipsoid, more or less hispid in the upper half, and smaller than 5 mm, with the exception of C. basutorum (5-7.2 mm) and some forms of C. killickii. This clade of four species is endemic to Lesotho and South Africa and they occur at medium-high elevations (1,400-3,150 m; but C. killickii has been exceptionally found at 550 m). They are typically found in open and dry grasslands, although C. killickii also occur in mesophilous meadows and C. burkei in temporary flooded meadows and edges of streams.
(C) C. capensis and C. sciocapensis Carex capensis and C. sciocapensis have basal sheaths that are bladeless and the lowest bract of the inflorescence is not sheathing. The remaining species of the section have basal sheaths with lamina (except sometimes only the lowest with lamina), and a sheathing lowest bract in the inflorescence (except C. basutorum, C. chermezonii and C. multispiculata). Carex capensis and C. sciocapensis are two species endemic to the southernmost areas of the Cape region (South Africa). Both species occur at low elevations (5-750 m) and C. sciocapensis can also be found at medium elevations (below 1,500 m).
Carex capensis inhabit open and sunny places whereas C. sciocapensis is common in shady places and margins and clearing of forest (and sometimes in fynbos areas).
(D) C. acocksii, C. perdensa, C. dregeana, C. spartea and C. esenbeckiana The clade grouping C. acocksii, C. perdensa, C. dregeana, C. spartea and C. esenbeckiana is characterized by fibrous basal sheaths (although in C. perdensa are entire or scarcely fibrous) and by smooth utricles up to 5.5 mm (rarely 6 mm in C. esenbeckiana). This clade of five species has the broadest distribution. Carex dregeana, C. spartea and C. esenbeckiana are distributed across S and E Africa (C. dregeana also disjunctly in Angola and Madagascar) from low to high elevations (4-2,850 m). Carex spartea is the species with the northernmost distribution in the section, reaching SE Arabian Peninsula. In contrast with these widely distributed species, C. acocksii and C. perdensa are restricted endemics in South Africa, where they are found at medium-high elevations (1,200-1,950 m). All of these species occur in open places, except C. esenbeckiana, which is found in shady places in afromontane forests.
(E) C. pseudorufa, C. ludwigii, C. kukkoneniana, C. badilloi and C. bolusii The clade grouping C. pseudorufa, C. ludwigii, C. kukkoneniana, C. badilloi and C. bolusii is characterized by basal sheaths entire to slightly fibrous and by scabrid utricles towards the apex. These species are mainly distributed in South Africa and Lesotho, while C. kukkoneniana reaches further north to Tanzania. They are found in edges of streams and other wet places at medium-high elevations, although C. badilloi and C. bolusii can also be found in grasslands and open places.
Carex gordon-grayae Carex gordon-grayae, long confused with C. esenbeckiana (Clade D), shows a number of distinctive morphological characters that do not match any of the groups described so far: (i) basal sheaths not or scarcely fibrous, typical of all groups except the Clade D; (ii) broad leaves (up to 9 mm), as in Clade A species; (iii) subsessile or shortly pedunculated partial inflorescences, which is common in the Clades B, C and D; (iv) lowest bract sheathing, unlike Clade C; (v) hyaline glumes and pyramidal style base, as in C. acocksii; and (vi) long (5.4-7.9 mm) utricles narrowly linear and gradually attenuated in a long beak, unlike the D and E Clades. Moreover, this species is a rare endemic to SE of KwaZulu-Natal and E of Eastern Cape, where it inhabits forest near the coast, unlike the remaining species of the section, except C. esenbeckiana and C. sciocapensis.

Cytogenetics
Chromosome number evolution in Carex is dominated by dysploid events (Roalson, 2008;Hipp, Rothrock & Roalson, 2009;Escudero et al., 2012) with some species presenting large dysploid series (Luceño & Castroviejo, 1991;Hipp et al., 2010). The section Schoenoxiphium does not seem an exception to this general pattern in genus Carex, and it displays a wide range of chromosome numbers, from 2n = 24 to 2n = 88 (C. spartea and C. lancea, respectively; Table 2, Figs. 4 and 5). However, the distribution of the counts is rather discontinuous either overall and within some of the clades. High numbers have been reported for the Clade A (2n = 60, 62 and 88), Clade B (2n = 66, 70-72), Clade C (2n = 68, 72) and part of the Clade E (2n = 64). The consistent presence of relatively high chromosome numbers in all these clades suggests a likely high ancestral number for the section. The most diverse and karyologically complex would be Clade D, in which the chromosome counts are reduced to half (2n = 24, 26, 27, 30, 32, 34) and in Clade E (2n = 34, 36), excluding C. pseudorufa (2n = 64). This conspicuous reduction of chromosome numbers is probably due to a massive series of fusion events that have occurred through the diversification of the lineage, rather than several polyploid events in the Clades A, B, C and E. In fact, fusion events have been inferred to happen ca. 1.5 times as fission events in the non-Siderostictae Carex (Supplementary Data 7 in Márquez-Corro et al., 2019b). Moreover, a preliminary study that is currently being carried out considering genome size variation among and within species of the section points to the fusion hypothesis, because genome sizes do not vary proportionally to chromosome number . However, the detection of an unusual high number within one of the two reduced lineages (i.e., C. pseudorufa) is very intriguing. Genome size of this species is yet unknown, so there are two possible hypotheses: either a rare polyploid event in C. pseudorufa or, at least, two convergent, independent fusion events in the reduced lineages (based on the topology retrieved in the RAD-seq phylogeny, see Fig. 4). Chromosome number variation of the section is very promising and posits possible evolutionary scenarios in which the establishment in different niches with sympatric species could be through karyotype-related adaptation, since most members of the section inhabit the Drakensberg area (including most of the Eastern Cape mountains). Etymology: From the Greek σχοῖνος (schoĩnos), rush, and χίφος (xíphos), sword; probably because of the shape and sharp edges of the leaves of some of its species.
Perennial herbs, not caespitose to densely caespitose. Rhizome with short to long internodes, brown. Flowering culms (4.5)10-180(200) cm, erect or, more rarely, nodding, acutely to obtusely trigonous, smooth to scabrid, 0.4-4 mm wide at the middle. Leaves (0.2)0.4-15(18) mm wide, shorter to longer than the inflorescence, soft to coriaceous, filiform to linear, flat, involute, canaliculate, carinate or plicate, usually scabrid at the margin and distal part of abaxial midrib, with straight to curled apex; ligule (0.1)0.3-12 (17) mm long. Basal sheaths entire to very fibrous, usually with lamina, but sometimes lowermost bladeless. Lowest bract of the inflorescence leaf-like, more rarely glumaceous or setaceous, shorter to longer than the inflorescence, not sheathing or with a sheath up to 84 cm long. Inflorescence branching 1-4 times, reduced to a single, terminal spike or, more frequently, composed by several panicles and/or spikes, one terminal and the remaining lateral (partial inflorescences) sessile to longly pedunculate, overlapping to distant, erect to nodding. Glumiform perigynia and glumiform cladoprophylls rarely present. Tubular cladoprophylls always present except in C. acocksii and unispicate morphotypes of C. killickii. Utriculiform cladoprophylls frequently present. Male glumes usually ovate to lanceolate, more rarely oblong, obovate or elliptic, brown to yellowishbrown, with a green central band, ending in an aculeate mucro or ariste, more rarely acuminate, acute or obtuse. Female glumes usually ovate, more rarely elliptic, lanceolate, obovate, oblong or suborbicular, brown, reddish-brown or yellowish-brown, with a green central band, ending in an aculeate mucro or ariste, more rarely acuminate, acute or obtuse. Unisexual utricles present or, sporadically, absent, linear, lanceolate, oblong, ovate or elliptic in outline, straight or, more rarely, curvate or arcuate, straw-coloured, yellowish-brown or brown when mature, smooth to densely aculeate, especially in the upper tiers, with numerous, very prominent veins across the entire surface, rarely faintly veined, suberect to patent, gradually attenuate or abruptly contracted into an smooth to aculeate, bidentate, slightly bifid, split, truncate or irregular beak; rachilla usually reaching the apex or protruding from it, more rarely rudimentary to reaching the half of the utricle length. Bisexual utricles wide and obliquely truncate at the apex, rarely absent. Achenes ovate-trigonous or, more frequently ellipsoid-trigonous to oblong-trigonous, straw-coloured, yellowish-brown to dark-brown when mature, tipped by an obtusely trigonous to subterete, neck-like or, more rarely, pyramidal, persistent style base.

Distribution
Endemic to the Northern Cape province in South Africa [27 CPP]. Figure 6A.

Conservation
Previous assessments of the species performed at the national level in South Africa (Victor, 2002;Raimondo et al., 2009;SANBI, 2020) had consistently resulted in the category Vulnerable (VU). However, a recent reevaluation of the conservation status at global level following criteria, categories and guidelines from IUCN (2012IUCN ( , 2017 has resulted in the category Critically Endangered (CR) . The species is only known from two locations and appears to be severely threatened by overgrazing pressure by livestock and the possible impacts of climate change.

Etymology
The epithet honours Basotho people, inhabitants of the country currently named Lesotho.  Figures 8C and 10.

Conservation
Not considered of conservation concern at the national level in South Africa, and thus categorized as Least Concern (LC) (SANBI, 2020; sub Schoenoxiphium basutorum). Rhizome caespitose, with short internodes moderately stout, light-brown to dark-brown. Flowering culms (4)12-67(95) cm long, erect, obtusely trigonous, smooth, occasionally with any minute prickle to the apex, leafy from one third to nearly half of its length, (0.3)0.8-1.2(1.5) mm wide at the middle. Leaves (0.5)1.7-3.8(5.5) mm wide, shorter, rarely longer (in dwarf plants) than the inflorescence, slightly to moderately rigid, straight at the apex, light-green to somewhat glaucous, flat to ± V-shaped in cross-section, slightly to moderately scabrous along the edges and usually along the abaxial midrib; adaxial surface usually finely papillose; ligule (0.5)0.8-3(4) mm long. Basal sheaths with lamina or, more rarely, the lowermost bladeless, entire, somewhat broken or slightly fibrous. Lowest bract of the inflorescence leaf-like, from half of the inflorescence length to equaling it, with a sheath (9)17-51 (73) Figure 6D.

Notes
The name C. bolusii C.B.Clarke has been considered synonymous with C. schimperiana Boeckeler (a synonym of C. spartea Wahlenb.; Global Carex Group, 2015  circumscription. This is based on the slightly fibrous basal sheaths of the type materials, as typically occurs in C. bolusii, and not completely fibrous, as shared by the C. spartea specimens. Moreover, the leaf and culm width are similar to the measurements observed in C. bolusii.  (1995)).

Habitat
Open and sunny places on shale soils, commonly observed in after-fire vegetation (Fynbos Biome: mostly in Renosterveld); 5-750 m.

Etymology
From the latin capens-is, from the Cape, in reference to the South African region where it was discovered and to where it is endemic.

Conservation
Considered as Least Concern (LC) at the national level in South Africa (SANBI, 2020; sub Schoenoxipium ecklonii).

Notes
We have been unable to locate the lectotype of Schoenoxiphium ecklonii Nees, designated by Kukkonen (1983). Kukkonen considered this species as distinct (Kukkonen, 1983), as also confirms the revision labels he left in numerous herbarium specimens (M. Luceño, 2021, personal observation). After the examination of the type of C. capensis Thunb., we consider S. ecklonii to be a synonym of the former, in view of the multiple specimens revised by Kukkonen whose taxonomic identity matches that of the C. capensis type. Rhizome caespitose, moderately stout, brown. Flowering culms 29-51 cm long, erect, obtusely trigonous, scabrid to the apex, leafy up to 1/3 of its length, 1-1.2 mm wide at the middle. Leaves 1.6-4.2 mm wide, shorter than the inflorescence, moderately rigid, more or less glaucous, flat in cross-section, straight at the apex; ligule not measured. Basal sheaths not or scarcely fibrous, usually with lamina, but those of the sterile shoots bladeless. Lowest bract leaf-like, longer than the inflorescence, not sheathing. Inflorescence c. ⅓ of the length of the culm, branching up to 3 times; partial inflorescences 2-5, the lowest short-pedunculate and more or less distant, the upper sessile to shortly pedunculate and overlapping. Glumiform perigynia and glumiform cladoprophylls not seen. Tubular cladoprophylls not seen. Utriculiform cladoprophylls present. Male glumes up to 4.5 mm long, lanceolate to ovate, yellowish-brown to brown, with a green central band, acute to acuminate. Female glumes 3.4-4.5 mm long, ovate, yellowish-brown to brown, shortly aristate, with a green central band. Unisexual utricles 4.9-7 × 0.6-0.8 mm, linear to narrowly ellipsoid, stipitate, strongly arcuate to straight, straw-coloured to yellowishbrown when mature, with numerous prominent veins across the entire surface, suberect, gradually attenuate into an obliquely truncate beak up to 2 mm long; rachilla reaching to slightly protruding from the apex of the utricle; bisexual utricles with the beak widely and obliquely truncate. Achenes up to 6 mm long, oblong.

Distribution
Endemic to N Madagascar (Tsaratanana mountains), only known from the type collection.

Etymology
Named after Henri Chermezon (1885-1939), French botanist specialized in tropical sedges, mainly from Madagascar. He was who originally described this species. Not Evaluated (NE).

Notes:
To our knowledge, the only known collection of this species are those of the type material, which consists of two specimens in whose photograph (P-00536708) we have relied on the preparation of this description. Our measurements match those contained in the protologue (Chermezon, 1923), but differ significantly from those published by Kukkonen (1983). This is especially pronounced regarding the length of the fertile culms and of the achenes. We have taken this last character from the author of the species, who was astonished by the unusual length (6 mm) of the fruit and used this character to differentiate C. chermezonii from C. multispiculata (Chermezon, 1923 2)3.7-4(4.1) × 0.7-1 mm, linearoblongoid to narrowly elipsoid, distinctly stipitate, straight, straw-coloured to yellowishbrown when mature, smooth or disperse and shortly aculeate at the apex, with numerous prominent veins across the entire surface, erect to suberect, gradually attenuated into a more or less bidentate beak 0.6-1 mm; rachilla reaching or protruding a little from the apex of the utricle or, more rarely, much protruding from the mouth and bearing some small, sterile glumes at the top, but then, utricles wide and obliquely truncate. Bisexual utricles wide and asymmetrically truncate. Achenes (2.1)2.3-2.8(2.9) × 0.6-1 mm, oblongtrigonous, yellowish-brown, tipped by a short, obtusely trigonous, persistent style base.  Figure 6H.

Etymology
From the latin distinctus-a-um, distinct, distinguishable to the eye, probably because the species is easily recognizable because of its aspect.

Notes
Carex dregeana is the only species in the section whose rachilla does not reach the apex of the unisexual utricles and, moreover, they are frequently reduced to a barely visible, vestigial elongation of the branch at the base of the utricle. This species is easily recognizable both for that peculiarity and for the very rare presence of bisexual utricles and utriculiform cladoprophylls. Another character that allows the correct identification of this species from the similar ones, as C. spartea and C. esenbeckiana, is the utricle beak length, that does not lengthen beyond 0.3 mm. In addition, the upper partial inflorescence bracts usually present a wide base and an evident scarious margin, that elongates in a subulate apex. This species hybridizes with certain frequency with C. spartea, resulting in numerous intermediate morphotypes, characterised by the rachillas that do not reach the apex of the utricle, bisexual utricles sometimes present, bracts not or slightly widened at the base, and utricle beak up to 0.6 mm. These hybrids present some irregularities in the meiotic pairing (see Results, cytogenetic section).
Diagnosis: Similar in appearance to C. esenbeckiana Boeckeler, from which it differs by its wider leaves ((4.5)5.5-9 mm in C. gordon-grayae vs. (0.9)2-5(7) mm in C. esenbeckiana), the utricles (5.4-7.9 mm long, linear-oblong to narrowly ellipsoid, gradually attenuated in the beak in C. gordon-grayae vs. (3.1)3.8-5.5(6) mm long, ovoid to broadly ellipsoid, abruptly contracted in the beak utricles in C. esenbeckiana), and by its broadly pyramidal style base in C. gordon-grayae vs. shortly trigonous, neck-like style base in C. esenbeckiana. Rhizome laxly caespitose, with short internodes, moderately stout, medium to dark-brown. Flowering culms 29.5-65 cm long, obtusely trigonous, smooth, leafy up to half its length, 0.9-1.7 mm wide at the middle. Leaves (4.5)5.5-9 mm wide, shorter than the inflorescence, somewhat rigid, glaucous, flat in cross-section, scabrous along the edges, at least in the upper two-thirds; abaxial surface smooth, but scabrous in the upper third of the mibrid; adaxial surface papillose-aculeate near the margins of the distal half, straight at the apex; ligule 4.5-5.3 mm long. Basal sheaths broken to slightly fibrous, lowermost bladeless. Lowest bract of the inflorescence leaf-like, shorter than the inflorescence length, with a sheath 20-40 mm long. Inflorescence branching up to three times; partial inflorescences 3-5, very distant, except terminal ones; lateral from subsessile to shortly pedunculate, erect. Glumiform perigynia and glumiform cladoprophylls absent. Tubular cladoprophylls always present at the base of partial inflorescences and in some first order branches of lateral partial inflorescences, hyaline. Utriculiform cladoprophylls usually present at lower parts of developed partial inflorescences. Male glumes 2.9-4.2 × 0.9-1.4 mm, lanceolate to ovate, hyaline, with a green central band, acute to acuminate, usually with a scabrid acumen up to 1.1 mm long. Female glumes 4-6.5 × 1.3-1.9 mm, lanceolate to ovate, hyaline, with a narrow, green central band, with a scabrid acumen up to 2.5 mm long. Unisexual utricles 5.4-7.9 × (0.9)1.1-1.5 mm, linear-oblong to narrowly-ellipsoid, shortly stipitate, straight to very slightly curved, green to yellowish brown when mature, sparsely aculeate at the apex of the beak, with numerous prominent veins across the entire surface, erect, gradually attenuated into an obliquely truncate, hyaline at the apex beak 1.4-2.5 mm long; rachilla protruding from the apex up to 2.5 mm. Bisexual utricles similar to unisexal ones, but more widely mouthed. Achenes 3.5-4.3 × 0.9-1.3 mm, ellipsoidtrigonous, yellowish-brown, tipped by a broadly pyramidal and shortly neck-like at the lower part, persistent style base.
Habitat Shady places, mainly in margins and clearing of forests, close to the coast (Indian Ocean Coastal Belt Biome: Pondoland-Ugu Sandston Coastal Sourveld); 200-400 m.

Etymology
The epithet honours Professor Kathleen D. Gordon-Gray (1918-2012, a South African Botanist, as homage to her excellent works in KwaZulu-Natal Cyperaceae, especially in the former genus Schoenoxiphium. In the holotype she noted: "This may possibly be an unusual specimen of Sch. lehmannii (Nees) Steudel, but the much wider leaves and longer utricles (7 mm) make this doubtful … Field investigation needed". Rhizome loosely to densely caespitose, with short internodes, slender, brown. Flowering culms (8.5)15-50(95) cm long, acutely trigonous, smooth or, more rarely, somewhat aculeate at the apex, leafy usually up to half (upper third) of its length, 0.3-0.9(1.5) mm wide at the middle. Leaves 0.2-1(3.6) mm wide, shorter to longer than the inflorescence, soft to somewhat rigid, light green, canaliculate to involute more rarely flat in crosssection, more or less scabrous along the edges; abaxial surface smooth or scabrid in the midrib; adaxial surface smooth; somewhat curved or scarcely curled at the apex; ligule 0.3-1.2 mm long. Basal sheaths usually not or scarcely fibrous, more rarely very fibrous, with lamina. Lowest bract of the inflorescence usually glumaceous with setaceous apex or, more rarely, leaf-like, shorter to longer than the inflorescence, not sheathing except when the lowest partial inflorescence is long-pedunculate and clearly separate from the remaining ones, in this case sheath up to 25(40) mm long. Inflorescence reduced to a terminal, androgynous spike or branching up to 3 times; partial inflorescences 1-5(7), overlapping and sessile or, more rarely, the lowest one clearly distant and longpedunculate, patent, erect-patent or somewhat reflexed except the lowest one distant and pedunculate that is suberect when present. Glumiform perigynia and glumiform cladoprophylls absent. Tubular cladoprophylls absent or hyaline when the lowest partial inflorescence is distant and long-pedunculate. Utriculiform cladoprophylls present except in unispicate inflorescences. Male glumes (3)3.5-4.2(4.5) × (0.9)1.2-1.5(1.7) mm, ovatelanceolate, obovate or elliptical, brown with a green central band, acute to acuminate, frequently ending in an arista up to 0.8 mm. Female glumes 3.1-4.2 × 1.2-2 mm, lanceolate to ovate, pale to dark brown with a green central band, acute, acuminate to aristate, sometimes with a scabrid acumen up to 1.8 mm. Unisexual utricles 3.8-5.3(7.2) × 0.5-1.2 mm, narrowly linear-oblongoid to narrowly elipsoid, distinctly stipitate, usually straight, more rarely slightly arcuate, straw-coloured to yellowish-brown when mature, smooth to dispersely and shortly hispid in the upper half, with few to numerous faintly to strongly prominent veins across the entire surface, patent at the maturity, gradually attenuated into a more or less irregular beak up to 1 mm; rachilla reaching or protruding a little from the apex of the utricle or, more rarely, much protruding from the mouth and bearing some small, sterile glumes at the top. Bisexual utricles wide and asymmetrically truncate. Achenes (2.)2.5-3.2(3.6) × 0.4-1 mm, oblong-trigonous, yellowish to palebrown, tipped by a short, obtusely trigonous to long-pyramidal, persistent style base.  Figure 15D.

Etymology
Named after Donald Joseph Boomer Killick (1926Killick ( -2008, South African botanist specialized in Drakensberg flora, who collected the type material of this species.

Conservation
Not considered of conservation concern at the national level in South Africa, and thus categorized as Least Concern (LC) (see SANBI, 2020, sub Schoenoxipium molle; sub S. filiforme).

Notes
This species is the most morphologically variable in the section, in particular its inflorescence structure. This has caused taxonomic delimitation problems (e.g. the former Schoenoxiphum molle and S. strictum; see Gordon-Gray, 1995; SANBI, 2020). The common forms of C. killickii present fertile culms of 20-50(60) cm, canaliculate to involute, filiform leaves, unispicate or branched inflorescences and narrowly ellipsoid, smooth or slightly scabrid, utricles up to 5.3 × 0.9-1.2 mm long, with numerous prominent veins. Nevertheless, the specimens that inhabits summits of the Drakensberg mountains are shorter (8.5-30 cm), with unispicate inflorescences and unisexual utricles narrowly linear, smooth or rarely slightly scabrid, 5-7.2 × 0.5-0.8 mm, mostly without numerous veins and, however noticeable, hardly prominent. This form corresponds to the C. killickiii Nelmes type material, described from the mountain summits of Lesotho. Moreover, transition morphotypes towards the more common forms appear in lower altitudes from those mountains. Regarding the type material of Schoenoxiphium filiforme Kük. (1910), described from the Great Winterberg Mountain range (Eastern Cape, north of Adelaide), it shows unispicate inflorescences and fertile culms of 20-25 cm, but the utricles are more similar to the common forms. Additionally, as it is shown in the phylogeny of Fig. S2, the sample from the Lesotho summits is nested within more typical forms of the species (unispicate or with branched inflorescences). However, given the molecular variability of this taxon and the fact that a single sample from the summit form was included in the RAD phylogeny, we cannot rule out that the summit morphotype corresponds to a different taxon. That can only be resolved by carrying out a phylogeographic study of the species. Moreover, densely caespitose forms inhabit the lower slopes of the Drakensberg (1,800-2,300 m), forming tussocks with fertile culms up to 70(95) cm, flat or slightly canaliculate leaves up to 2.5(3.6) mm width that surpass the culms length, inflorescences always branched and utricles sparsely hispid towards the apex or hispid just in the lower half. This morphotype corresponds to the material described as Schoenoxiphium molle Kukkonen (1983). Likewise, in areas with similar habitats appear forms with smooth culms and less wider leaves, flat or canaliculate, that have been described as S. strictum Kukkonen. Between these two and the typical forms of the species, a multitude of intermediates phenotypes can be found, so we consider that, until further phylogeographic studies are carried out, these forms should be included under the wide morphological variability of C. killickii.

Conservation
Not evaluated (NE).  Rhizome caespitose with more or less short internodes, stout, dark-brown. Flowering culms (50)60-110(170) cm long, erect, acutely trigonous, smooth, leafy up to half its length, (1)1.5-2 mm wide at the middle. Leaves (3)4-8(8.8) mm wide, shorter than the inflorescence, moderately coriaceous, green, flat in cross-section, but with an adaxial groove in the midrib area and trigonous to the apex, very scabrous along the edges and also along the abaxial midrib; adaxial surface smooth; usually curved at the apex; ligule 0.7-1.5(2) mm long. Basal sheaths entire to scarcely fibrous, with lamina. Lowest bract of the inflorescence leaf-like, shorter than the inflorescence length, with a sheath 40-60 mm long. Inflorescence occupying between ⅓ and ½ of the length of the culm, branching up to 4 times; partial inflorescences (8)11-14(16), the 3-7 lowest distant, pedunculate, nodding, with the part of the peduncle protruding from the sheath much shorter than the linear fertile part, the upper subsessile to shortly pedunculate and overlapping. Glumiform perigynia present, unisexual or bisexual. Glumiform cladoprophylls present. Tubular cladoprophylls present at the base of the distant partial inflorescences, hyaline. Utriculiform cladoprophylls absent. Male glumes 4.1-6.4(6.9) × (1.1)1.5-(2.2) mm, ovate-lanceolate to ovate, yellowish-brown to brown, with a green central band, acuminate or ending in an aculeate mucro or ariste up to 1 mm long. Female glumes 5-6.2 × 1.8-2.2 mm, lanceolate to ovate, straw-coloured to pale brown, with a green central band, acuminate, ending in an aculeate mucro up to 1(1.7) mm long. Unisexual utricles 5.5-6.1 × 0.7-1 mm, narrowly linear to narrowly oblong, stipitate, straight, straw-coloured to pale brown when mature, smooth, more rarely scabrous in the upper tiers, with numerous prominent veins across the entire surface, suberect, gradually attenuate in a more or less split, more or less scabrous beak up to 1.7 mm long; rachilla reaching to protruding from the apex up to 0.6 mm. Bisexual utricles absent. Achenes 3.5-4.5 × 0.6-1.2 mm, oblong-trigonous, pale to dark-brown when mature, tipped by a longly pyramidal, persistent style base.

Etymology
From the latin lancea-ae, spear, probably because of the shape of its broadly linear leaves.

Conservation
Not considered of conservation concern at the national level in South Africa, and thus categorized as Least Concern (LC) (SANBI, 2020; sub Schoenoxiphium lanceum).

Conservation
The species has been evaluated as Least Concern (LC) at global level (IUCN, 2018). However, this was based on a distribution range that may likely include populations belonging to other species (C. kukkoneniana). It has also been evaluated as LC at the national level in South Africa (SANBI, 2020; sub Schoenoxiphium rufum).

Notes
When this species and C. bolusii C.B. Clarke are sympatric, it is possible to observe individuals showing intermediate morphological features between both taxa, probably due to hybridization. References to this species for the countries placed north of South Africa (see Kukkonen, 1983) belong to C. kukkoneniana.

Habitat
Edges of stream and waterfalls, damp meadows, and other damp places in mountains (Grassland Biome, Drakensberg Grassland, Mesic Highveld Grassland and Subscarpment Grassland); 1,100-2,800 m.

Etymology
From the Latin multus-a-um, many, and spicula-ae, spikelet, because of its very branched inflorescence which is composed of numerous spikelets.

Conservation
Not considered of conservation concern at the national level in South Africa, and thus categorized as Least Concern (LC) (SANBI, 2020; sub Schoenoxiphium madagascariense).

Notes
Two vouchers are kept in P with the number 2501 of Perrier de la Bâthie, one of them (P-s. n.) contains a complete and typical specimen of the species including two fertile culms, while the other (P-00540579) includes a less typical individual with just a fertile culm, so we have designated as a lectotype the first of them.

Etymology
From the Latin prefix per, very, and adjective densus-a-um, dense, because of the densely caespitose habit of this plant.

Distribution
Endemic to the eastern slopes of the Drakensberg range in KwaZulu-Natal (South Africa).

Etymology
From the Greek ψεyδής (pseudo, resembling but not equalling) and the Latin rufus-a-um (red), alluding to the resemblance of this species to Carex ludwigii, which was formerly known as Schoenoxiphium rufum.

Conservation
Considered as Least Concern (LC) at the national level in South Africa (SANBI, 2020; sub Schoenoxiphium burttii).
Notes Kukkonen (1986) indicated that the holotype of S. burttii was at H, but a thorough search in this herbarium (H. Väre, 2021, personal communication) has revealed that the specimen is lost, so the isotype at E is selected as the lectotype. Rhizome caespitose, with very short internodes, stout, pale-brown to dark-brown. Flowering culms (25)30-90(130) cm long, erect, acutely trigonous, smooth or, rarely, very dispersely aculeate to the apex, leafy up to ⅓(⅔) of its length, 2-3(3.8) mm wide at the middle. Leaves (4.7)6.5-11.5(18) mm wide, shorter than the inflorescence, more rarely longer, quite rigid, light green, plicate in cross-section, scabrous along the edges and usually also along the abaxial midrib; adaxial surface smooth to scabrid on the keels at the apex; straight at the apex; ligule up to 2 mm long. Basal sheaths with lamina or the lowermost bladeless, entire to somewhat fibrous. Lowest bract of the inflorescence leaf-like, longer than the inflorescence, with a sheath (18)20-40(84) mm long, distichous and hiding the inflorescence when young. Partial inflorescences 6-10(14), erect, branching up to 3(4) times, lowermost pedunculate and more or less distant, and uppermost subsessile. Glumiform perigynia usually absent. Glumiform cladoprophylls present at the base of the second order branches. Tubular cladoprophylls always present at the base of the lower partial inflorescences, sometimes split almost to the base. Utriculiform cladoprophylls rare, more or less split. Male glumes (4)5-7 × (1)1.7-3 mm, ovate-lanceolate to elliptic, yellowish-brown to brown, with a green central band, acute or, more frequently, ending in an aculeate mucro or arista up to 0.7 mm long. Female glumes (5)6.5-8.6(9) × (1.5)2-2.5(3) mm, lanceolate, ovate or elliptic, brown to yellowish, with a green central band, ending in a smooth to slightly aculeate mucro up to 2(3.6) mm long. Unisexual utricles (6)7-9.5(10) × 0.9-1.1 mm, narrowly linear, straw-coloured to brownish when mature, stipitate, straight, smooth, with numerous prominent veins across the entire surface, erect, gradually attenuated into an irregular beak up to 3 mm long, rarely split almost to the base of the utricle (glumiform perigynium); rachilla usually protruding from the apex up to 1(1.5) mm. Bisexual utricles widely and obliquely truncate at the apex. Achenes (4.2)4.8-6.1 × 0.8-1 mm, oblong-trigonous, straw-coloured to dark brown when mature, tipped by an obtusely trigonous to pyramidal, persistent style base.

Habitat
Stony meadows and, more rarely, edges of streams and pools in mountains (Grassland Biome: Drakensberg Grassland and Mesic Highveld Grassland); 1,400-3,100 m.

Etymology
Named after Herold Georg Wilhelm Johannes Schweickerdt , German botanist, who collected an important number of plants in South Africa, mainly in Mpumalanga and KwaZulu-Natal, but also in Mozambique and Zimbabwe. The herbarium of the Pretoria University (PRU) was named in his honour.

Etymology
From the Greek σκῐᾱ́(skiā), shade, and the Latin capens-is, from Cape region, in reference to the fact that it grows in shady areas of humid forests and its similarity to C. capensis. Iconography Figures 32B and 33.

Conservation
It has been considered Near Threatened (NT) at the national level in South Africa due to its restricted range (with a substantial portion of its habitat lost in the recent past because of exploitation of native forests and timber plantations) and competition with alien invasive plants (SANBI, 2020; sub Schoenoxiphium altum).

Notes
This species is very closely related to C. capensis; in fact, both taxa are scarcely differentiated from a molecular point of view (see Phylogenetic section and Fig. 4); however, most individuals of both taxa are easily separated by its morphological features (see descriptions of both species). Nevertheless, specimens exhibiting intermediate morphology and ecology can be found, mainly in mountain areas, but also in Cape Peninsula, where some intermediate specimens and similar forms to C. sciocapensis inhabit in sunny places. Deeper systematic studies are needed to determine the existence of one or more cryptic species and to check if hybridization processes are taking place between these two taxa. Kukkonen (1986) indicated that the holotype of S. altum was at H, but a thorough search in this herbarium (H. Väre, 2021, personal communication) has revealed that the specimen is lost, so the isotype at PRE is selected as the lectotype.

Notes
This species has been often mistaken with the short, narrow leaves and small utricles (3.5-4.2 mm long) forms of C. esenbeckiana, from which it is differentiated because of: (i) the light green color of C. spartea against the ashen green or bluish-green of C. esenbeckiana, (ii) lower ratio of beak:body of the utricle length in C. spartea, (iii) the very short, obtusely trigonous (rarely slightly and shortly neck-like), persistent style base of C. spartea against the distinctly neck-like style base of C. esenbeckiana, and (iv) C. spartea inhabits sunny meadows, whereas the habitat of C. esenbeckiana includes areas of permanent shade, generally in forest understories. Carex spartea has also been mistaken with C. bolusii, but the latter present noticeable prickles in the utricle beak (very rarely some specimens show the beak almost smooth), basal sheaths entire to slightly fibrous, and smooth, obtusely trigonous culms, whereas C. spartea presents a smooth utricle beak-very rarely, a few individuals from Eastern Cape show some utricles with very disperse, minute prickles towards the apex, basal sheaths generally strongly fibrous and culms more or less acutely trigonous, sometimes with some prickles sparse towards the apex. Finally, C. spartea is easily differentiated from C. dregeana because of the rachilla length, that in the latter reaches a maximum of ½(¾) of the utricle length, whereas in C. spartea equals or surpasses the utricle length. These species are also distinguishable by the superior partial inflorescences bracts: very wide and with a scarious margin in C. dregeana, and narrower without bearing the scarious margin in C. spartea.
The specimens of C. spartea from its northern distribution tend to present longer leaves that frequently surpass in length the culms. However, in those areas there are also populations with leaves shorter than the culms, as well as intermediate specimens.

CONCLUSIONS
We have here presented a fully updated and integrative monograph of Carex section Schoenoxiphium based on morphological, molecular and cytogenetic data. We recognize 21 morphologically well delimited species, and one of them, C. gordon-grayae, has been described here as a new species. The 20 species included in the phylogenetic study are placed in five well supported clades, except C. acocksii (weakly supported here as sister of Clade D, but see Márquez-Corro et al., 2020) and C. gordon-grayae (an independent lineage). Monophyly has been confirmed for all sampled species except for C. sciocapensis that was revealed as paraphyletic, probably due to recent divergence. For the first time, we have reported cytogenetic counts for this section, made on 44 populations and 15 taxa; we have observed a conspicuous reduction of chromosome numbers, probably due to a massive series of fusion events that have occurred through the diversification of the lineage, rather than several polyploid event. Further work is needed to (i) investigate the presence of cryptic species in Clades B and C, (ii) elucidate the phylogenetic position of C. gordon-grayae, and (iii) evaluate the potential role of ecological specialization and karyotype-related adaptation in the diversification of the section.