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. 2025 Aug 11;261:99–123. doi: 10.3897/phytokeys.261.157741

Reticulation within Sporobolus: recognition of two new sections, Acinifolii and Thellungia, and a new genus, Hyalolemma (Poaceae, Chloridoideae, Zoysieae, Sporobolinae)

Paul M Peterson 1,✉, Konstantin Romaschenko 1, Robert J Soreng 1, Yolanda Herrera Arrieta 2
PMCID: PMC12361921  PMID: 40837556

Abstract

We present a molecular DNA phylogeny utilizing four plastid regions (rps16–trnK spacer, rps16 intron, rpl32–trnL spacer, ndhA intron) and the nuclear ribosomal internal transcribed spacer (ITS) region, investigating 123 species of subtribe Sporobolinae. We also aimed to assess the generic limits of Sporobolus, characterize possible subgeneric relationships among species in the genus, and identify hypothesized reticulation events. The core Bayesian tree, based on combined and congruent plastid and ITS regions, is well resolved, and 11 sections within a monophyletic Sporobolus are strongly supported. We describe a new genus, Hyalolemma, with two species and include a key; erect two new sections within Sporobolus, S.sect.Acinifolii and S.sect.Thellungia; and make three new combinations, Hyalolemmacompactum, H.somalensis, and Sporoboluscollinus. The names Eragrostiscollina Trin. and Sporoboluscompactus Clayton are lectotypified.

Key words: Classification, ITS, lectotypification, phylogeny, plastid DNA sequences, Poaceae, Sporobolus , systematics, taxonomy

Introduction

The genus Sporobolus R. Br. (dropseed) includes approximately 220 species worldwide and is placed in subtribe Sporobolinae Benth., tribe Zoysieae Benth., and subfamily Chloridoideae Kunth ex Beilschm. (Soreng et al. 2022). Sporobolus is characterized by single-flowered spikelets (rarely 3–27-flowered), 1-veined (occasionally 3-veined) lemmas, fruits with free pericarps (commonly swelling and mucilaginous when wet, forcibly ejecting the seed), and ligules that are a line of hairs or a ciliate membrane (Peterson et al. 2003, 2004, 2014a; Giraldo-Cañas and Peterson 2009).

The most compelling subgeneric classification of Sporobolus was based on a phylogeny derived from DNA sequence data (of 144 Sporobolus species), using four plastid regions (rpl32–trnL, ndhA, rps16–trnK, rps16) and one nuclear marker (ITS), ultimately recognizing 11 sections and 11 subsections (Peterson et al. 2014a, b). This classification was somewhat controversial, since it subsumed within Sporobolus three long-established genera: Calamovilfa (A. Gray) Hack. ex Scribn. & Southw., Crypsis Aiton, and Spartina Schreb.; and two multi-flowered species: Eragrostisadvena (Stapf) S.M. Phillips [≡ Thellungiaadvena Stapf ≡ Sporobolusadvenus (Stapf) P.M. Peterson] and E.megalosperma F. Muell. ex Benth. [≡ S.megalospermus (F. Muell. ex Benth.) P.M. Peterson]. A recent phylogenomic analysis of Sporobolus, using nuclear Angiosperm353 probes and whole plastomes based on a smaller sample (16 species), confirmed the monophyly of Sporobolus, with Spartina [S.sect.Spartina (Schreb.) P.M. Peterson & Saarela] and Crypsis [C.sect.Crypsis (Aiton) P.M. Peterson] as derived clades within Sporobolus (GPWG III 2024). It is interesting to note that Stapf (1920) indicated that the new species (Thellungiaadvena) found among wool refuse near the Derendingen Mill in Switzerland “was found to be very like that of a Sporobolus but distinguished by the presence of several (mostly three and sometimes four) florets in each spikelet.”

We continue to advance the concept of core phylogeny and its usefulness, especially in phylogenetic studies of large genera with complex relationships among their members using conventional genetic data such as cpDNA and ITS nrDNA sequences. We consider a core phylogeny to represent an evolutionary pattern among species based only on direct descent, excluding taxa or individuals with genomes of multiple origins. Following this concept in our phylogenetic studies, we split the analysis into two main phases. First, we develop a phylogenetic tree using only the “core” set of available taxa or individuals presumably having a single origin. Then, we rerun the analysis with the addition (usually one taxon at a time) of taxa or individuals with genetic data (plastid or nuclear) for which multiple origins were detected. This taxon duplication approach (Pirie et al. 2008; Pelser et al. 2010; Soreng et al. 2010; Peterson et al. 2015a, 2016, 2020, 2021, 2025) uses the core phylogeny as a framework to test the affinities of species based on different types of genetic data. Eventually, these affinities can be characterized, providing inferences about species origins and geographical distribution. In most cases, a core phylogeny demonstrates a better-developed topology of the species and stronger support for phylogenetic groups compared to previous studies, as seen in Agrostis L. and Calamagrostis Adans. (Saarela et al. 2017; Peterson et al. 2021, 2025). We attribute this to the elimination of incongruent data from analysis, including confounding ITS data that likely result from incomplete genomic introgression, gene flow, or incomplete concerted evolution. The tendency of nrDNA to homogenize during different stages of genomic introgression and to reflect to varying degrees the affinities with parental species is well documented (Fuertes Aguilar et al. 1999; Bailey et al. 2003; Liu et al. 2020; Wang et al. 2023). Compared to low-copy gene analysis, ITS data can sometimes indicate an intermediate position for hybrid species, i.e., between the locations of presumable parental taxa (Romaschenko et al. 2013), or provide an erroneous phylogenetic position for such species due to putative long branch attraction (Peterson et al. 2021). Of particular interest is the formation of strongly supported ITS groups with shared morphological features that encompass species with divergent plastid lineages (Peterson et al. 2021). We identify these as “floating ITS groups” because they often show little affinity to other clades, while their inclusion in the analysis may weaken backbone support (e.g., the Deschampsiagrostis group of Calamagrostis; see Peterson et al. 2021). Though the origin of floating ITS groups is ambiguous, it might involve the following processes: hybridization between species representing distant lineages; extensive gene flow between hybrid and parental populations; incomplete genomic introgression and formation of confounding (via homogenization) ITS sequences; separation and geographical isolation of individuals with similar confounding ITS sequences and distinct plastid sequences; reduction of gene flow; and the formation of new species and subsequent evolutionary diversification. We found it useful to test our phylogenies for the presence of floating ITS groups, since these clades often share morphological characteristics that are important descriptors of their evolutionary history (Wang et al. 2023).

In our previous phylogeny of the Sporobolinae (Peterson et al. 2014a), we listed two incertae sedis categories: one species, Sporobolussomalensis Chiov., outside of Sporobolus, and 13 species with uncertain affinities within the genus. In this paper, we take a closer look at the basal lineage consisting of Sporobolusacinifolius Stapf, S.albicans Nees, and S.tenellus (A. Spreng.) Kunth. We also track species that exhibit incongruent ITS versus plastid marker alignment, such as S.consimilis Fresen., S.robustus Kunth, S.scabridus S.T. Blake, and S.tourneuxii Coss.; and species in S.sect.Crypsis and S.subsect.Subulati P.M. Peterson. Additionally, we include two more multi-flowered species, Eragrostiscollina Trin. from Persia and Sporobolusramigerus (F. Muell.) P.M. Peterson, Romasch. & R.L. Barrett from Australia, to test their affinities, and include Sporoboluscompactus Clayton, an ally of S.somalensis (Clayton 1970; Barrett et al. 2020).

Material and methods

Taxon sampling

We sampled 135 individuals representing 122 species (55%) of Sporobolus. A complete list of taxa, including authorities, voucher information, and GenBank numbers, is presented in Appendix 1. Most of these DNA sequences were previously published in GenBank and were initially used in Peterson et al. (2014a). We include 18 new sequences in GenBank, representing two species, Eragrostiscollina and Sporobolusniliacus (Fig. & De Not.) P.M. Peterson, both extracted from herbarium specimens housed in the United States National Herbarium (US).

We designed our study to characterize relationships among species of Sporobolus and relatives, principally in the Sporobolinae Benth. (including Psilolemma S.M. Phillips), and including an outgroup from the Zoysiinae Benth. (Urochondra C.E. Hubb. and Zoysia Willd.) (Peterson et al. 2014a; Soreng et al. 2022).

Phylogenetic methods

All procedures related to the sequencing of the plastid and ITS regions were performed in the Laboratory of Analytical Biology at the Smithsonian Institution. Detailed methods for DNA extraction, amplification, and sequencing are given in Romaschenko et al. (2012) and Peterson et al. (2010a, b, 2012, 2014a, 2015a, b, 2016). We used Geneious Prime v.2020.1.4 (Kearse et al. 2012) for contig assembly of bidirectional sequences of the rps16–trnK spacer, rps16 intron, rpl32–trnL spacer, ndhA intron, and ITS regions, and MUSCLE (Edgar 2004) to align consensus sequences and adjust the final alignment. Phylogenetic trees were constructed from the three combined cpDNA and nrDNA datasets (see Appendix 1) using partitioned maximum likelihood analysis implemented in IQ-TREE 2 (Minh et al. 2020; Chernomor et al. 2016). The best-fit evolutionary models for partitions were inferred using ModelFinder Plus (MFP; Kalyaanamoorthy et al. 2017) based on the Akaike Information Criterion. In the partition model used for maximum likelihood analysis, we specified a substitution model for each DNA region (rps16–trnK spacer, rps16 intron, rpl32–trnL spacer, ndhA intron, and ITS; see Table 1), allowing each partition to have its own evolutionary rate. Support was assessed using the approximate Bayes test (aBayes; Anisimova et al. 2011) and 10,000 bootstrap replicates (BS; Felsenstein 1985). Support values with aBayes ≥ 0.95 and BS ≥ 95% were interpreted as strong support.

Table 1.

Characteristics of the five regions, rps16-trnK, rps16 intron, rpL32-trnL, ndhA intron, ITS, and parameters used in phylogenetic analyses indicated by Akaike information criterion (AIC).

rps16-trnK rps16 intron rpL32-trnL ndhA intron Combined plastid data ITS Overall
Total aligned characters 975 964 937 1236 4112 798 4910
Number of sequences/success 118 (87.4%) 119 (88.1%) 135 (100%) 99 (73.3%) 471 (87.2%) 135 (100%) 606 (89.8%)
Parsimony informative sites 166 134 194 212 706 401 1107
Optimal log-likelihood -3803.1 -3396.8 -4442.9 -5304.4 -12989.6
Substitution model TVM+F+G4 GTR+F+ I+I+R2 TPM3u+F+ I+I+R2 TPM3u+F+ I+I+R2 SYM+I+G4
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Principles and phases of phylogenetic reconstruction

Phylogenetic reconstructions were performed in three main phases. The first phase included preliminary Bayesian and bootstrap analyses (trees from preliminary searches not shown), designed to detect hard incongruences between ITS and plastid data; construction of the preliminary core phylogeny; individual testing of specimens with incongruences against the preliminary core phylogeny; and construction of the final core phylogeny (Fig. 1). The second phase (Fig. 2) included a series of individual searches for the incongruent species to identify the correct affiliation of their ITS and plastid sequences, added independently to the core matrix using the taxon duplication approach. The third phase involved identifying patterns among discordant splits between the ITS and plastid data and constructing overall phylogenies representing putative affinities of the incongruent ITS and plastid sequences tested against the core phylogeny. Procedurally, the three-phased core phylogenetic analysis using the taxon duplication approach is described in Peterson et al. (2025).

Figure 1.

Figure 1.

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Core Bayesian tree inferred from combined plastid (rpl32-trnL, ndhA, rps16-trnK, rps16) and ITS sequences of the Sporobolinae with Hyalolemma and Psilolemma and Sporobolus showing sectional classification including S.sect.Acinifolii with geographic distribution (color). Thick black branches in the phylogram indicate a bootstrap of 95–100 and/or an aBayes of 0.95–1.00. Scale bar = 1% substitutions per site.

Figure 2.

Figure 2.

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Reticulate origins of species within Sporobolus showing sectional classification and geographic distribution (color). Thick black branches in the phylogram indicate a bootstrap of 95–100 and/or an aBayes of 0.95–1.00. Scale bar = 1% substitutions per site. A. Origins of Eragrostiscollina (= Sporoboluscollinus), S.advenus, S.megalospermus, and S.ramigerus (= S.sect.Thellungia); Sporobolussect.Crypsis, S.consimilis, S.humilis subsp. minor, S.oxylepsis, and S.robustus; B. Origins of Sporoboluskentrophyllus, S.subulatus, and S.verdcourtii (= S.subsect.Subulati); S.ozarkanus, S.scabridus, and S.tourneuxii.

Assessment of incongruence and data-combining strategy

Combining all congruent data provides better resolution of phylogenetic trees, strengthens support for nodes, and maximizes the informativeness and explanatory power of the character data used in the analysis (Huelsenbeck and Cunningham 1996). The plastid and ITS topologies resulting from Bayesian and bootstrap analyses were inspected for conflicting nodes with support values of aBayes ≥ 0.95 and/or BS ≥ 95%. If no supported incongruences were found, plastid and ITS sequences were combined and used in the core phylogenetic analysis (Fig. 1). This analysis (combined plastid and ITS sequences) included a subset of Sporobolus species representing 11 sections and 11 subsections classified in Peterson et al. (2014a), two unclassified species of Sporobolus (S.compactus and S.somalensis), Psilolemmajaegeri (sister to Sporobolus), Eragrostiscollina, and outgroups Zoysiajaponica Steud. and Urochondrasetulosa (Trin.) C.E. Hubb. (Zoysiinae). These two outgroup species were selected because they occur within the Zoysieae and have been shown to be sister to the Sporobolinae (Peterson et al. 2010a, 2014a).

Taxon duplication approach

A taxon duplication approach (Pirie et al. 2008; Gillespie et al. 2010; Pelser et al. 2010; Soreng et al. 2010; Peterson et al. 2015a, 2016, 2020, 2021, 2025) was applied to 26 specimens representing 19 species for which incongruence between plastid and ITS data was detected (sets 2A and 2B, Appendix 1). Each of these specimens was assigned two entries in the matrices: one containing only ITS and one containing only plastid sequences. This technique allowed us to identify the placements of the incongruent ITS and plastid sequences in the context of the Sporobolus core phylogeny. To avoid mutual influence of confounding ITS sequences, each specimen was analyzed separately before being assigned to one of two expanded datasets (sets 2A and 2B), each including samples with a similar pattern of incongruence between ITS and plastid data representing characteristic ITS/plastid discordant splits. The number of specimens added to the core dataset (dataset 1: 105 specimens) to form the extended datasets was as follows: dataset 2A – 20 specimens; dataset 2B – 10 specimens. The outgroups in the expanded sets included the same species used in the core phylogeny (Fig. 1).

We used this taxon duplication approach to resolve our phylogenetic tree, minimizing the diffusing effects of taxa with strongly supported incongruence between plastid and ITS data, while still showing the placements of the plastid and ITS sequences in relation to the taxa in the core phylogeny. This allowed us to hypothesize multiple origins and elucidate complex evolutionary histories within phylogenetic groups.

Results

Phylogenetic analyses

Eighteen sequences (18/608 = 3%) in our study are newly reported in GenBank, and 97% (590/608) are previously published sequences (Appendix 1) generated for earlier studies (Peterson et al. 2010a, 2012, 2014a). Ten point four percent (70/671) of the sequences (ITS and plastid) in our dataset are missing. Total aligned characters for individual regions and other parameters are shown in Table 1.

Core phylogeny

The core Bayesian tree, based on combined, congruent plastid regions (rps16–trnK spacer, rps16 intron, rpl32–trnL spacer, ndhA intron) and ITS, is well resolved, and 11 sections within a monophyletic Sporobolus (including the new section Acinifolii) are strongly supported (BS = 95–100; aBayes = 0.95–1.00) (Fig. 1). The first split within Sporobolus includes three species–Sporobolusacinifolius, S.albicans, and S.tenellus (S.sect.Acinifolii, the new section) from Africa–which are sister to the remaining species in the genus. The next split includes species in sect. Sporobolus [including the type S.indicus (L.) R. Br.] from Africa, Australia, and the Western Hemisphere, and these are sister to the remaining species. The following split consists of two strongly supported clades (BS = 95–100; aBayes = 0.95–1.00): one with four sections, resolving as (Triachyrum (Hochst. ex A. Braun) Veldkamp (Fimbriati Veldkamp (Pyramidati P.M. Peterson + Virginici Veldkamp))), sister to a clade of five sections, resolving as (Airoides (Torr.) P.M. Peterson + Cryptandri P.M. Peterson) (Clandestini P.M. Peterson (Calamovilfa (A. Gray) P.M. Peterson + Spartina (Schreb.) P.M. Peterson & Saarela)). The latter five-section clade includes species mainly from North America (the “North American clade”), whereas the four-section clade includes species from Africa, the Western Hemisphere, Australia, and Europe.

Sister to Sporobolus in our core tree is a strongly supported clade (BS = 97, aBayes = 0.95) that includes two accessions of Psilolemmajaegeri + (Sporoboluscompactus + S.somalensis) (Fig. 1). The latter two species are genetically variable, with two nucleotide substitutions in ITS, seven nucleotide substitutions in the plastid markers, and five insertion/deletion events in the plastid markers, ranging from 2–46 nucleotide gaps. They are morphologically distinct, differing in lower glume shape and length and in upper glume length.

Phylogenetic trees with taxon duplication (including species with incongruent ITS and plastid sequences)

The taxon duplication trees (Fig. 2A, B) provide insight into plastid- and ITS-based relationships among Sporobolus species with incongruent plastid and ITS data.

Based on plastid markers, four accessions of Eragrostiscollina (PLC1) form a clade sister to the remaining Sporobolus species after the split of sect. Sporobolus (Fig. 2A). Based on ITS, these same four accessions of E.collina are sister to S.ramigerus (S.advenus + S.megalospermus). Together, these four species form a strongly supported clade (ITSC), which is weakly supported as sister to Sporobolussect.Crypsis (Aiton) P.M. Peterson (ITSB). Two members of sect. Crypsis collected in North America, Sporobolusniliacus (Fig. & De Not.) P.M. Peterson (Baja California, Mexico) and S.schoenoides (L.) P.M. Peterson (California, USA), are introductions. The native distribution of species in sect. Crypsis is Africa, Arabia, and Asia. The E.collina + (S.ramigerus (S.advenus + S.megalospermus)) clade is morphologically distinct in having multi-flowered spikelets, unlike most Sporobolus species. Based on plastid markers, S.megalospermus and S.advenus + S.ramigerus (PLC2) form a grade between the S.buckleyi Vasey + S.palmeri Scribn. clade and sect. Clandestini (Fig. 2A), all native to North America (American clade). Based on ITS, the S.consimilis + S.robustus clade (ITSA) is placed between sects. Triachyrum and Crypsis (Fig. 2A). Based on plastid data, S.robustus is sister to S.humilissubsp.minor Veldkamp (PLA1, B1) and is embedded in sect. Virginici, with S.humilissubsp.minor coming from sect. Crypsis (ITSB), whereas S.consimilis aligns as sister to sect. Crypsis (PLB2).

Based on plastid markers, S.tourneuxii (PLD) is sister to four sections resolving as (Triachyrum (Fimbriati (Pyramidati + Virginici))), whereas based on ITS (ITSD), S.tourneuxii is sister to sects. Virginici + Pyramidati (Fig. 2B). The S.kentrophyllus (K. Schum. ex Engl.) Clayton + (S.subulatus Hack. −S.verdcourtii Napper) clade aligns in different locations within S.sect.Pyramidati: sister to subsect. Actinocladi P.M. Peterson (ITSE) and embedded within subsect. Pyramidati P.M. Peterson (PLE). Likewise, S.scabridus S.T. Blake aligns in different locations within S.sect.Pyramidati: sister to S.caroli Mez in subsect. Actinocladi (PLF) and sister to S.centrifugus (Trin.) Nees+ S.cordofanus (Hochst. ex Steud.) Coss. −S.marginatus Hochst. ex A. Rich. (ITSF) in subsect. Pyramidati. Sporobolusozarkanus Fernald [≡ S.vaginiflorusvar.ozarkanus Fernald] aligns in different locations: sister to S.splendens Swallen (PLG) in sect. Airoides and sister to S.clandestinus (Biehler) Hitchc. + S.vaginiflorus (Torr. ex A. Gray) Alph. Wood (ITSG) in sect. Clandestini.

Taxonomy

. Hyalolemma

P.M.Peterson, Romasch. & Soreng, gen. nov.

7039D922-B982-5776-9BD1-1E9226AFA119

urn:lsid:ipni.org:names:77367026-1

Type.

Hyalolemmasomalensis (Chiov.) P.M. Peterson, Romasch. & Soreng ≡ Sporobolussomalensis Chiov.

Description.

Cushion forming perennials, arising from stout, branching stolons densely clothed in imbricate cataphylls below, innovations extravaginal. Culms 6–30 cm tall, erect. Leaf sheaths open for most of their length, glabrous or with pustulate-based hairs, the hairs up to 3 mm long, hyaline; ligules ≤ 0.–4 mm long, a line of hairs; blades 0.5–8 cm long, 1.2–2.2 mm wide, flat, stiff, glaucus, and pungent, sometimes with pustulate hairs scattered along the margin. Inflorescence a panicle 2–13 cm long, 2–7 cm wide, ovate, diffuse, branches capillary. Spikelets 1.2–2.2 mm long, 1-flowered, lanceolate, laterally compressed to subterete; glumes shorter to as long as spikelet, hyaline; lower glumes 0.3–1.2 mm long, orbicular to narrowly oblong, apex obtuse to erose; upper glumes 0.7–2 mm long, 1-veined, oblong, apex obtuse; lemmas 1.2–2 mm long, oblong to ovate, 1- or 3-veined, when 3-veined the lateral veins only visible on lower ¼ to ½, hyaline, apex obtuse to truncate, often erose and minutely ciliate; paleas 2-veined. Flowers perfect; lodicules 2; anthers 1–2 mm long, 3, purplish; ovary glabrous. Caryopses 1.2–1.6 mm long, elliptic, brownish with a free pericarp.

Etymology.

The name is derived from the Greek “hyalos,” meaning hyaline or transparent, combined with lemma (Greek).

Distribution.

Hyalolemma comprises two species found in northeastern Africa in Ethiopia and Somalia.

Key to the species of Hyalolemma

1 Lower glumes 0.3–0.5 mm long, orbicular; upper glumes as long as the spikelet H.compactum
– Lower glumes 0.5–1.2 mm long, narrowly oblong; upper glumes 1/2–2/3 as long as the spikelet H.somalensis
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. Hyalolemma compactum

(Clayton) P.M.Peterson, Romasch. & Soreng, comb. nov.

586DDD9D-7C0B-502F-A90F-1BFFBC679691

urn:lsid:ipni.org:names:77367028-1

  • Sporobolus compactus Clayton, Kew Bull. 25(2): 248. 1971. Type: Somalia [British Somaliland], Erigavo, 5500 ft, ubiquitous on plains, 26 Sep 1938, A.S. Mckinnon S.89 (lectotype, designated here: K000365246 [image!]; isolectotypes: K000365245 [image!], US-1815148!).

. Hyalolemma somalensis

(Chiov.) P.M.Peterson, Romasch. & Soreng, comb. nov.

55A52384-D079-5477-8593-6D62667C89D1

urn:lsid:ipni.org:names:77367029-1

  • Sporobolus somalensis Chiov., Annuario Reale Ist. Bot. Roma 6: 169. 1896. Type: Somali Ogaden, 7 Aug 1891, L. Robecchi-Brichetti 485 (holotype: FT000424 [image!]; isotype: G00022752 [image!]).

  • = Sporobolusvariegatus Stapf, Kew Bull. 1907: 218. 1907. Type: Somalia, Somaliland, found occasionally in small quantities between Veoholle and Upper Sheikh, Jul 1903, [Lieutenant Colonel] Appleton s.n. (holotype: K000365243 [image!]).

. Sporobolus sect. Acinifolii P.M.Peterson, Romasch. & Soreng, sect. nov.

18C55241-AAA3-5843-B483-B49D899FFF17

urn:lsid:ipni.org:names:77367030-1

Type.

Sporobolusacinifolius Stapf, Fl. Cap. 7: 581. 1900.

Description.

Mat forming perennials with elongated and much branched or short rhizomes, innovations intravaginal. Culms 6–43 cm long with 1–5 nodes, glabrous. Leaf sheaths open for most of their length; ligules 0.2–0.3 mm long, a line of hairs; blades 0.5–12 cm long, 1–3 mm wide, flat, glabrous, apex obtuse to acuminate, occasionally with cartilaginous margins. Inflorescence a panicle 2–15 cm long, open with effuse to capillary or sometimes dichotomously branched or spiciform with loosely ascending branches. Spikelets 1–2.5 mm long, 1-flowered, lanceolate, subterete; glumes shorter to as long as the spikelet, 1-veined, hyaline or sometimes membranous; lower glumes 0.25–0.5 as long as upper glumes; upper glumes 0.5–1 as long as the floret, apex acute to obtuse; lemmas 1–2.5 mm long, 1- or 3-veined, ovate, membranous, apex obtuse to acute; paleas 2-veined. Flowers perfect; lodicules 2; anthers 0.7–1.9 mm long; ovary glabrous. Caryopses 0.8–1.1 mm long, ellipsoid to globose, brownish with a free pericarp.

Species.

Sporobolusacinifolius, S.albicans, S.tenellus.

Distribution.

Southern Africa.

. Sporobolus sect. Thellungia

(Stapf) P.M.Peterson, Romasch. & Soreng, comb. et stat. nov.

8467329F-75BD-5297-B1E7-599B0E283DE0

urn:lsid:ipni.org:names:77367032-1

Type.

Sporobolusadvenus (Stapf) P.M. Peterson, Taxon 63(3): 1232. 2014 ≡ Thellungiaadvena Stapf ≡ Eragrostisadvena (Stapf) S.M. Phillips.

Description.

Caespitose perennials often with short to long rhizomes; innovations mostly intravaginal. Culms 60–300 cm tall, erect, sometimes geniculately ascending. Leaf sheaths open for most of their length, glabrous, sometimes coriaceous near base; ligules 0.1–0.8 mm long, a line of hairs; blades 10–30 cm long, (0.5–) 1–6 mm wide, flat to involute, sometimes convolute and filiform, smooth, scabrous near the margins, glabrous. Inflorescence a panicle 5–50 cm long, spiciform and contracted (S.advenus, S.megalospermus, sometimes S.ramigerus) or open (S.collinus), diffuse, ovate. Spikelets 3–17 mm long, 2–15 (–27)-flowered, linear, lanceolate, ovate to oblong, occasionally cleistogamous, sometimes with a rachilla extension (S.advenus); glumes shorter than the spikelet, 1-veined; lower glumes 0.5–0.9 as long as the upper glume; upper glumes 1.25–4 mm long, apex acute to obtuse; lemmas 1.8–3 mm long, 3-veined, sometimes 1-veined, ovate or lanceolate, hyaline, membranous to cartilaginous, often olive-green to dark greenish purple, apex acute, sometimes obtuse to truncate; paleas 1/2 to as long as the lemma, 2-veined, with wide flaps usually wider than the body and usually splitting along the midline; Flowers perfect; lodicules 2, cuneate; stamens 3, anthers 0.3–2 mm long, usually greenish; ovary glabrous. Caryopses 0.9–1.2 mm long, 3- or 4-angled, strongly laterally compressed to ovoid, globose, sometimes stipitate (S.ramigerus) with a free pericarp.

Species.

Sporobolusadvenus, S.megalospermus, S.ramigerus, and one more below.

Distribution.

Australasia and Central Asia.

. Sporobolus collinus

(Trin.) P.M.Peterson, Romasch. & Soreng, comb. nov.

7299AA06-2B47-5FD5-8B88-F590BFC51515

urn:lsid:ipni.org:names:77367031-1

  • Eragrostis collina Trin., Mém. Acad. Imp. Sci. St.-Pétersbourg, Sér. 6, Sci. Math. 1(4): 413. 1830 ≡ Poacollina (Trin.) K. Koch, Linnaea 21(4): 405. 1848, nom. illeg. hom., non Poacollina Host. ≡ Poatatarica Fisch. ex Griseb., Bess. Cat. Krzem. Suppl. 2: 13. 1814, nom. nud. ≡ Eragrostistatarica (Fisch. ex Griseb.) Nevski, Trudy Bot. Inst. Akad. Nauk S.S.S.R., Ser. 1, Fl. Sist. Vyssh. Rast.: 226. 1937 ≡ Eragrostistatarica (Fisch. ex Griseb.) Henrard, Blumea 3(3): 425. 1940, isonym. Type: Persia, E deserto Rhymnico, Hbr. Gorenki, F.E.L. Fischer s.n. (lectotype, designated here: LE-TRIN-2319.06 [microfiche image!]).

  • = Airaarundinacea L., Sp. Pl. 1: 64. 1753 ≡ Festucaarundinacea (L.) Lilj., Utkast Sv. Fl. (ed. 2): 47. 1798, hom. Illeg, non Festucaarundinacea Schreb. ≡ Poaarundinacea (L.) Link, Hort. Berol. [Link] 1: 176. 1827 ≡ Eragrostisarundinacea (L.) Roshev., Fl. SSSR 2: 319. 1934 ≡ Boriskelleraarundinacea (L.) Terechov, Del. Sem. Hort. Reg. Bot. Kujbyshev: 13. 1938 ≡ Psilanthaarundinacea (L.) Tzvelev, Bot. Zhurn. (Moscow & Leningrad) 53: 311. 1968. Type: Turkey, Aras Valley, 1100–1200 m, 19 Jul 1966, P.H. Davis 46876 (neotype, designated by S.A. Renvoize in Cafferty et al. 2000, Taxon 49(2): 244: K; isoneotype: E, US-2597835!).

Notes.

We are rejecting the earlier lectotype by Tzvelev (1976) in Zlaki SSSR 635. Nauka Publishers, Leningrad Section, Leningrad, designating Snowitz 518 as the lectotype for Eragrostiscollina because it was not mentioned by Trinius in the original publication.

Discussion

The E.collina + (S.ramigerus (S.advenus + S.megalospermus)) clade is a biogeographically defined lineage occurring in Australia (S.advenus, S.megalospermus, and S.ramigerus are endemic to southern Australia, including Queensland and New South Wales) and extending to central and southwest Asia (Lazarides 1997; Palmer et al. 2005). Eragrostiscollina is endemic to Iran, Iraq, Crimea, Transcaucasia, central Asia around the Caspian and Aral seas to Kazakhstan and Kyrgyzstan, Turkistan, Uzbekistan (Syr-Darya), China (Xinjiang), Russia (Volga River basin from Dagestan to Siberia), and eastern Syria and Turkey (Bor 1970; Tan 1985; Palmer et al. 2005; Chen and Peterson 2006). Morphologically, these three species share multi-flowered spikelets with 2–27 florets and 3-veined (occasionally 1-veined) lemmas, two characteristics that are uncommon among species attributed to Sporobolus. The plastid lineage (PLC1) of Eragrostiscollina may have been donated through a hybridization event involving an unknown, extinct ancient lineage characterized by ancestral states (e.g., multi-flowered spikelets) from dry areas of eastern Asia, whereas the ITS (ITSC) signal clearly aligns as sister to S.advenus + S.megalospermus, all with an Australasian biogeography (Fig. 2A). Conversely, S.advenus and S.megalospermus may have received their plastid lineage from a presumed species in the American clade (Fig. 2A). In Australia, S.advenus and S.megalospermus are found in disturbed alluvial flats and other disturbed sites, which could have facilitated a chloroplast capture event from an American donor. Based on their ITS and morphological similarities, we place the four species in S.sect.Thellungia and transfer E.collina to Sporobolus.

Resolution among species sharing ITS and plastid genes between S.sect.Crypsis and S.sect.Virginici is more challenging. Based on ITS, the S.consimilis + S.robustus pair (ITSA), both primarily confined to Africa, shows that the latter species received its plastid haplotype (PLA1, B1) from a species probably within S.sect.Virginici, while S.consimilis received its plastid haplotype (PLA2) from an ancient hybridization event with a probable member of S.sect.Crypsis. Sporobolushumilissubsp.minor, sister to S.mitchellii (Trin.) C.E. Hubb. in S.sect.Crypsis (ITSB), subsect. Helvoli P.M. Peterson, received its plastid haplotype from a member of S.sect.Virginici, as it is sister to S.robustus (PLA1, B1). Previously, Peterson et al. (2014a) included S.humilissubsp.minor and S.robustus in S.sect.Virginici due to shared morphological characteristics such as narrow, densely spikeleted panicles or densely spikeleted primary branches (S.robustus), upper glumes longer than the floret, and stoloniferous growth (Baaijens and Veldkamp 1991). However, S.consimilis is still retained as incertae sedis, since it never forms a clade within S.sect.Crypsis, although plastid markers place it as sister to S.sect.Crypsis (PLA2) (Fig. 2A). Morphologically, S.consimilis is a large tussock-forming perennial with short underground rhizomes, sometimes forming looping stolons. Its panicles have spike-like primary branches bearing closely appressed spikelets, and the upper glumes are longer than the floret (Clayton 1974).

The three species representing S.subsect.Subulati–S.kentrophyllus + (S.subulatus − S.verdcourtii)–are evidently reticulate in origin. They resolve within S.sect.Pyramidati based on plastid data, with their plastid donor (PLE) likely a species within S.subsect.Pyramidati P.M. Peterson, where S.ioclados (Nees ex Trin.) Nees was placed. However, based on ITS, the same clade (ITSE) is sister to S.subsect.Actinocladi (Fig. 2B). These three species share the following morphological traits: caespitose perennials, often stoloniferous; panicles with whorled primary branches bare on the lower one-quarter to one-half; lower glumes one-third to three-quarters the length of the spikelets; upper glumes two-thirds to equal the length of the spikelet; and ellipsoid caryopses 0.8–2 mm long (Peterson et al. 2014a). They occur from Africa to India, with S.kentrophyllus and S.verdcourtii sometimes placed within S.ioclados (Plants of the World Online 2025).

The Australian species S.scabridus most likely received its plastid haplotype (PLF) from a member of S.subsect.Actinocladi but possesses an ITS marker similar to other members of S.subsect.Pyramidati (ITSF) (Fig. 2B). Morphologically, S.scabridus resembles S.actinocladus (F. Muell.) F. Muell., S.caroli Mez, and S.coromandelianus (Retz.) Kunth; all four species have quadrangular caryopses that are smooth on the ventral surface, with an embryo about half the length of the grain (Clayton 1974; Simon and Jacobs 1999). Species with African origins are found in both subsects Actinocladi and Pyramidati, increasing the likelihood of hybridization–particularly with the widespread S.coromandelianus.

Based on either plastid or ITS markers, Sporobolustourneuxii does not align within any existing section of Sporobolus (Fig. 2B). Broader sampling may reveal an affiliation with existing sections or subsections; otherwise, a new section may be warranted. Sporobolustourneuxii resembles S.respolianus Chiov. morphologically, both having short and stout panicle branches with spikelets crowded near the tips. However, the latter species has creeping stolons (Cope 1995; Phillips 1995). Both species occur along the Indian Ocean coastlines, overlapping in the Arabian Peninsula and the Horn of Africa.

Within the North American clade, Sporobolusozarkanus most likely received its plastid haplotype (PLG) from S.splendens, its strongly supported sister in S.sect.Airoides (Fig. 2B). Based on ITS, S.ozarkanus (ITSG) is sister to S.clandestinus + S.vaginiflorus. Sporobolusozarkanus, originally described by Fernald (1933) and later placed as a variety of S.vaginiflorus by Shinners (1954), is morphologically distinct from S.vaginiflorus by having sparsely hairy sheath bases, glumes longer than the florets, and 3-veined lemmas (Peterson et al. 2003). Sporobolusozarkanus, S.clandestinus, and S.vaginiflorus are found in the central and eastern United States and eastern Canada, whereas S.splendens is native to central and southern Mexico (Espejo Serna et al. 2000; Peterson et al. 2003).

We chose to recognize S.compactus and S.somalensis in a new genus, Hyalolemma, within the Sporobolinae, since together they are separated by a long branch indicating extensive genetic divergence from Psilolemma. Morphologically, Psilolemma differs from Hyalolemma by having a spiciform inflorescence composed of racemes arranged along a central axis; spikelets 3–3.8 mm long, 4–14-flowered; glumes membranous; lemmas 3–3.8 mm long with three conspicuous dark green veins, membranous; and caryopses 1.1–1.2 mm long (Phillips 1974). Both genera are endemic to the Horn of Africa (Fish et al. 2015).

Although our sampling of Sporobolus species is incomplete, we can make general observations about the biogeographical history of these grasses based on their current distribution. Our phylogeny suggests that Sporobolus originated in Africa, since Psilolemma, Hyalolemma, and S.sect.Acinifolii (all basal lineages) are from that region. The nearest sister group to the Sporobolinae–Urochondra (Somalia, Sudan to NW India) + Zoysia (temperate and tropical Asia, Australasia)–are members of the Zoysieae (Cope 1995; Phillips 1995; Clayton et al. 2006). The Zoysieae clade has an estimated mean crown age of 19.27 (14–25.23) mya and stem age of 36.82 (34.5–39.68) mya (Gallaher et al. 2022). The ancestral area estimate for Zoysieae (stem) is Afrotropical (46%) and Neotropics + Afrotropics (11%) (Gallaher et al. 2022).

As a worldwide genus, Sporobolus represents a rather “tight” evolutionary entity, with core species (those arising via orderly evolutionary descent rather than reticulate evolution) comprising about 81% of all sampled species (55% of the genus). This is significantly higher than in other widespread genera such as Calamagrostis–64% (57% sampled; Peterson et al. 2021) or Agrostis–55% (70% sampled; Peterson et al. 2025). In this respect, Sporobolus is closer to more localized genera like Muhlenbergia, with 96% core species (82% sampled; Peterson et al. 2010b, 2018), or Bouteloua, with 77% core species (98% sampled; Peterson et al. 2015b).

The phylogeography of S.sect.Thellungia resembles that of Australian Agrostis (Phase VI of phylogeographic distribution of Agrostis; Peterson et al. 2025). It includes the interaction (likely in dry areas of East Asia) of one of the most ancient, multiflowered Asian lineages–“proto-collinus”–and two derived, uniflowered, closely related but independent North American lineages–“proto-megalospermus” and “proto-advenus”–followed by the distribution of hybrids (all multiflowered) in Central Asia and Australia and their subsequent speciation. The origin of S.sect.Crypsis is likely African, although its paternal lineage remains unknown.

The involvement of species from S.sect.Triachyrum in the formation of sects. Crypsis and Thellungia is also possible. However, since no plastid lineages from Triachyrum species were found within these sections, we believe that Crypsis and Thellungia indeed represent floating ITS groups, and their sister placement to members of S.sect.Triachyrum is likely incidental, resulting from confounding ITS sequences.

Supplementary Material

XML Treatment for Hyalolemma
XML Treatment for Hyalolemma compactum
XML Treatment for Hyalolemma somalensis
XML Treatment for Sporobolus sect. Acinifolii P.M.Peterson, Romasch. & Soreng, sect. nov.
XML Treatment for Sporobolus sect. Thellungia
XML Treatment for Sporobolus collinus

Acknowledgments

We are grateful to Kanchi Gandhi and John Wiersema for assistance in Latinizing the sectional names and to Gloria Martínez-Sagarra and Eduardo Ruiz-Sanchez for suggesting improvements to the manuscript.

Appendix 1

Table A1.

List of specimens sampled. Taxon, voucher (collector, number, and where the specimen is housed), country of origin, specific data set, and GenBank accession for DNA sequences of rps16–trnK spacer, rps16 intron, rpl32–trnL spacer, ndhA intron, and ITS regions; bold indicates new accession; a dash (–) indicates missing data.

N Taxon Voucher Country Data set rps16–trnK rps16 rpl32–trnL ndhA ITS
1 Eragrostiscollina Trin. Davis 46876 (USZ) Turkey, A9 Kari 2A PV733880 PV733884 PV733875 – PV714800
2 Eragrostiscollina Trin. Field 303 & Lazar (US) Iraq 2A PV733881 PV733885 PV733876 – PV714801
3 Eragrostiscollina Trin. Nikitin 368 (US) Kazakhstan, Aqtöbe 2A PV733882 PV733886 PV733877 – PV714802
4 Eragrostiscollina Trin. Rechinger 1048 (US) Iran 2A PV733883 PV733887 PV733878 – PV714803
5 Psilolemmajaegeri (Pilg.) S.M. Phillips Peterson 24247, Soreng, Romaschenko & Mbago (US) Tanzania, Manyara 1, 2A, 2B KM011122 KM010919 KM010695 KM010535 KM010326
6 Psilolemmajaegeri (Pilg.) S.M. Phillips Peterson 24249, Soreng, Romaschenko & Mbago (US) Tanzania, Manyara 1, 2A, 2B KM011123 KM010920 KM010696 KM010536 KM010327
7 Sporobolusacinifolius Stapf Smook 3530 (US) South Africa, Northern Cape 1, 2A, 2B KM011153 KM010947 KM010727 KM010560 KM010354
8 Sporobolusactinocladus (F. Muell.) F. Muell. Saarela 1670, Peterson, Soreng & Judziewicz (US) Australia, Northern Territory 1, 2A, 2B KM011155 KM010950 KM010730 KM010563 KM010357
9 Sporobolusaculeatus (L.) P.M. Peterson Soreng 5469, Peterson & Sun Hang (US) China, Gansu 2A GU360599 GU360402 GU359841 GU359362 GU359238
10 Sporobolusaculeatus (L.) P.M. Peterson Soreng 7940, Johnson, Johnson, Dzyubenko, Dzyubenko & Schilnikov (US) Russia, Stavropol 2A JQ345233 JQ345275 JQ345316 JQ345205 JQ345163
11 Sporobolusacuminatus (Trin.) Hack. Guala 1372 & Filgueiras (US) Brazil, Goias 1, 2A, 2B KM011157 KM010952 KM010732 KM010565 KM010359
12 Sporobolusadvenus (Stapf) P.M. Peterson Belson s.n. (US) Australia, Queensland 2A KM011303 – KM010904 – KM010522
13 Sporobolusadvenus (Stapf) P.M. Peterson Lazarides 4185 (US) Australia, Queensland 2A KM011304 – KM010905 – KM010523
14 Sporobolusaeneus (Trin.) Kunth Irwin 25327, Onishi, da Fonseca, Souza, Reis dos Santos & Ramos (US) Brazil, Goias 1, 2A, 2B KM011159 KM010954 KM010734 – KM010361
15 Sporobolusafricanus (Poir.) Robyns & Tournay Peterson 24024, Soreng, Romaschenko & Abeid (US) Tanzania, Njomba Region 1, 2A, 2B KM011160 KM010955 KM010735 KM010567 KM010362
16 Sporobolusairoidessubsp.airoides (Torr.) Torr. Peterson 24587 & Romaschenko (US) Mexico, San Luis Potosí 1, 2A, 2B KM011163 KM010958 KM010738 KM010570 KM010365
17 Sporobolusalbicans Nees Smook 2459 & Russell (US) South Africa, Orange Free State 1, 2A, 2B – – KM010742 – KM010369
18 Sporobolusalopecuroides (Piller & Mitterp.) P.M. Peterson Soreng 7941, Johnson, Johnson, Dzubenko & Schilnikov (US) Russia, Stavropol 2A KM011116 KM010916 KM010688 KM010532 KM010320
19 Sporobolusalterniflorus (Loisel.) P.M. Peterson & Saarela Lakela 26537 (US) USA, Florida 1, 2A, 2B KM011127 KM010923 KM010700 KM010539 KM010330
20 Sporobolusanglicus (C.E. Hubb.) P.M. Peterson & Saarela Williams 2004-1 (UBC) Canada, British Columbia 1, 2A, 2B KM011130 KM010926 KM010703 KM010542 KM010333
21 Sporobolusarcuatus (K.E. Rogers) P.M. Peterson Rogers 42409, Sharp & Delgadillo (US) USA, Tennessee. 1, 2A, 2B KM011110 KM010912 KM010683 KM010528 KM010315
22 Sporobolusarenicola P.M. Peterson Gates 17021 (US) USA, Kansas. 1, 2A, 2B KM011113 KM010913 KM010685 KM010529 KM010317
23 Sporobolusatrovirens (Kunth) Kunth Peterson 24729, Romaschenko & Zamudio Ruiz (US) Mexico, Queretaro 1, 2A, 2B KM011170 KM010965 KM010747 KM010576 KM010374
24 Sporobolusaustralasicus Domin Peterson 14404, Soreng & Rosenberg (US) Australia, Western Australia 1, 2A, 2B KM011172 KM010967 KM010749 KM010578 KM010376
25 Sporobolusberteroanus (Trin.) Hitchc. & Chase Peterson 8753, Annable & Poston (US) Ecuador, Cotopaxi 1, 2A, 2B KM011174 – KM010751 – KM010378
26 Sporobolusblakei De Nardi ex B.K. Simon Latz 10662 (MEL) Australia, Northern Territory 1, 2A, 2B KM011175 KM010969 KM010752 KM010580 KM010379
27 Sporobolusbogotensis Swallen & García-Barr. Peterson 14970 & Refulio Rodriguez (US) Peru, Cajamarca 1, 2A, 2B KM011176 KM010970 KM010753 – KM010380
28 Sporobolusbrevipilis (Torr.) P.M. Peterson Strong 848, Kelloff, Schuyler, Wurdack & Churchill (US) USA, New Jersey 1, 2A, 2B KM011111 – KM010684 – KM010316
29 Sporobolusbrockmanii Stapf Gillett 4016 (US) Somalia, Hargesia 1, 2A, 2B KM011177 KM010971 KM010754 KM010581 KM010381
30 Sporobolusbuckleyi Vasey Lira 546, Martinez, Alvarez, Ramirez, Medrod & Gamboa (CIIDIR) Mexico, Campeche 1, 2A, 2B KM011178 KM010972 KM010755 KM010582 KM010382
31 Sporoboluscaroli Mez Speck 1915 (US) Australia, Queensland 1, 2A, 2B KM011183 KM010977 KM010760 KM010585 KM010387
32 Sporoboluscentrifugus (Trin.) Nees Hoener 2133 (US) South Africa, Lesotho 1, 2A, 2B KM011184 KM010978 KM010761 KM010586 KM010388
33 Sporobolusclandestinus (Biehler) Hitchc. Freeman 6687 (US) USA, Kansas 1, 2A, 2B KM011185 KM010979 KM010762 KM010587 KM010389
34 Sporoboluscoahuilensis Valdés-Reyna Peterson 10000, Annable & Valdes-Reyna (US) Mexico, Coahuila 1, 2A, 2B KM011190 KM010984 KM010767 KM010591 KM010393
35 Sporoboluscompactus Clayton Boaler B17 (US) Somalia 1, 2A, 2B – KM011075 KM010873 KM010654 KM010491
36 Sporoboluscompositus (Poir.) Merr. Brodovich 1305 (US) USA, Michigan 1, 2A, 2B KM011168 – KM010745 KM010574 KM010372
37 Sporobolusconfinis (Steud.) Chiov. Peterson 24303, Soreng, Romaschenko & Mbago (US) Tanzania, Arusha 1, 2A, 2B KM011191 KM010985 KM010768 KM010592 KM010394
38 Sporobolusconsimilis Fresen. Peterson 24252, Soreng, Romaschenko & Mbago (US) Tanzania, Manyara 2A KM011193 KM010987 KM010771 KM010595 KM010396
39 Sporoboluscontractus Hitchc. Perez 196 (CIIDIR) Mexico, Nuevo Leon 1, 2A, 2B KM011194 KM010988 KM010772 – KM010397
40 Sporoboluscordofanus (Hochst. ex Steud.) Coss. Laegaard 15973 (US) Zimbabwe 1, 2A, 2B KM011195 KM010989 KM010774 KM010596 KM010399
41 Sporoboluscoromandelianus (Retz.) Kunth Peterson 24269, Soreng, Romaschenko & Mbago (US) Tanzania, Shinyanga 1, 2A, 2B KM011198 KM010992 KM010777 KM010598 KM010402
42 Sporoboluscreber De Nardi Brown 498 (MEL) Australia, New South Wales 1, 2A, 2B KM011200 KM010994 KM010779 KM010600 KM010404
43 Sporoboluscryptandrus (Torr.) A. Gray Peterson 22003 & Saarela (US) Mexico, Chihuahua 1, 2A, 2B GU360631 GU360354 GU359914 GU359524 GU359208
44 Sporoboluscynosuroides (L.) P.M. Peterson & Saarela Hill 15630 (US) USA, Maryland 1, 2A, 2B KM011136 KM010931 KM010709 KM010546 KM010339
45 Sporobolusdiandrus (Retz.) P. Beauv. Peterson 14389, Soreng & Rosenberg (US) Australia, Western Australia 1, 2A, 2B KM011203 KM010997 KM010782 KM010603 KM010407
46 Sporobolusdinklagei Mez Hale 11 (US) Liberia, Cavalla Plantation 1, 2A, 2B – KM010998 KM010784 KM010604 KM010409
47 Sporobolusdomingensis (Trin.) Kunth Swallen 10669 (US) USA, Florida 1, 2A, 2B KM011205 KM010999 KM010785 KM010605 KM010410
48 Sporoboluseylesii Stent & J.M. Rattray Wiehe 717 (US) Malawi, Nyasaland 1, 2A, 2B – KM011000 KM010787 – KM010411
49 Sporobolusfarinosus Hosok. Wood 3275 & Perlman (US) Guam, Mariana Isl. 1, 2A, 2B KM011206 KM011001 KM010788 KM010606 KM010412
50 Sporobolusfertilis (Steud.) Clayton Gould 13535 (US) Sri Lanka 1, 2A, 2B KM011207 KM011002 KM010789 KM010607 KM010413
51 Sporobolusfestivus Hochst. ex A. Rich. Peterson 23853, Soreng, Romaschenko & Abeid (US) Tanzania, Lindi 1, 2A, 2B KM011209 KM011004 KM010791 KM010608 KM010415
52 Sporobolusfimbriatus (Trin.) Nees Peterson 24241, Soreng, Romaschenko & Mbago (US) Tanzania, Tanga 1, 2A, 2B KM011211 KM011006 KM010794 KM010610 KM010417
53 Sporobolusflexuosus (Thurb. ex Vasey) Rydb. Valdes-Reyna 2014 & Peterson (CIIDIR) Mexico, Coahuila 1, 2A, 2B KM011214 KM011009 KM010796 KM010612 KM010420
54 Sporobolusfoliosus (Trin.) P.M. Peterson & Saarela Reeder 6652 & Reeder (US) Mexico, Baja California Sur 1, 2A, 2B KM011138 KM010933 KM010711 KM010548 KM010341
55 Sporobolusgiganteus Nash Pase 2628 (US) USA, New Mexico 1, 2A, 2B KM011216 KM011011 KM010800 – KM010422
56 Sporobolusgreenwayi Napper Greenway 12526 (US) Tanzania, Monduli 1, 2A, 2B – KM011012 KM010801 KM010614 KM010423
57 Sporobolushelvolus (Trin.) T. Durand & Schinz Peterson 24217, Soreng, Romaschenko & Mbago (US) Tanzania, Tanga 2A KM011218 KM011014 KM010803 KM010615 KM010425
58 Sporobolusheterolepis (A. Gray) A. Gray Davidse 1910A (US) USA, Iowa 1, 2A, 2B KM011219 KM011015 KM010804 – KM010426
59 Sporobolushookerianus P.M. Peterson & Saarela Lewis 78-1013 (CAN) Canada, Alberta 1, 2A, 2B KM011140 KM010935 KM010713 KM010550 KM010343
60 Sporobolushumilissubsp.minor Veldkamp Clayton 5879 (US) Sri Lanka, Eastren Province 2A KM011220 KM011016 KM010805 KM010616 KM010427
61 Sporobolusindicus (L.) R. Br. Peterson 22025 & Saarela (US) Mexico, Chihuahua 1, 2A, 2B GU360630 GU360355 GU359913 GU359504 GU359209
62 Sporobolusinfirmus Mez Haines 332 (US) Nigeria, Igboora 1, 2A, 2B KM011222 KM011018 KM010807 KM010618 KM010429
63 Sporobolusioclados (Nees ex Trin.) Nees Smook 5920 (US) South Africa, Orange Free State 1, 2A, 2B KM011223 KM011019 KM010808 KM010619 KM010430
64 Sporobolusjacquemontii Kunth 15902 Peterson & Valdes-Reyna (US) Mexico, Tamaulipas 1, 2A, 2B KM011225 KM011021 KM010810 KM010621 KM010432
65 Sporobolusjunceus (P. Beauv.) Kunth Strong 2332 (US) USA, Florida 1, 2A, 2B KM011226 KM011022 KM010811 KM010622 KM010433
66 Sporoboluskentrophyllus (K. Schum. ex Engl.) Clayton Bogdan 3306 (US) Kenya 2B KM011228 KM011024 KM010813 KM010624 KM010435
67 Sporoboluslasiophyllus Pilg. Peterson 21879, Soreng & Sanchez Vega (US) Peru, Cajamarca 1, 2A, 2B GU360629 GU360356 GU359912 GU359505 GU359210
68 Sporoboluslaxus B.K. Simon Simon 4166 (MEL) Australia, Queensland 1, 2A, 2B KM011232 KM011028 KM010817 KM010626 KM010438
69 Sporoboluslinearifolius Nicora Reitz 5292 & Klein (US) Brazil, Santa Catarina 1, 2A, 2B – KM011029 KM010818 – KM010439
70 Sporobolusludwigii Hochst. Smook 2857 (US) South Africa, Orange Free State 1, 2A, 2B KM011233 KM011030 KM010819 KM010627 KM010440
71 Sporobolusmarginatus Hochst. ex A. Rich. Rattray 1654 (US) Zimbabwe, Matopos Res. Station 1, 2A, 2B – KM011033 KM010823 KM010628 KM010442
72 Sporobolusmaritimus (C.E. Hubb.) P.M. Peterson & Saarela Fernández Casas 5537, Castroviejo, Muñoz Garmendia & Susanna (US) Morocco, Tetouan 1, 2A, 2B KM011142 KM010937 KM010715 KM010552 KM010345
73 Sporobolusmegalospermus (F. Muell. ex Benth.) P.M. Peterson Blake 6966 (US) Australia, Queensland 2A KM011117 – KM010689 – KM010321
74 Sporobolusmegalospermus (F. Muell. ex Benth.) P.M. Peterson Lazarides 4215 (US) Australia, Queensland 2A KM011118 – KM010690 – KM010322
75 Sporobolusmegalospermus (F. Muell. ex Benth.) P.M. Peterson Lazarides 5647 (US) Australia, Queensland 2A KM011119 – KM010691 – KM010323
76 Sporobolusmichauxianus (Hitchc.) P.M. Peterson & Saarela Dirig 2812 (US) USA, Indiana 1, 2A, 2B KM011150 KM010944 KM010723 KM010557 KM010351
77 Sporobolusmicroprotus Stapf Laegaard 17894 & Traore (US) Senegal, Thies 2B KM011235 KM011035 KM010824 KM010629 KM010443
78 Sporobolusmitchellii (Trin.) C.E. Hubb. ex S.T. Blake Forster 22301 (MEL) Australia, Queensland 2A KM011236 – KM010826 – KM010444
79 Sporobolusmolleri Hack. Peterson 23978, Soreng, Romaschenko & Abeid (US) Tanzania, Ruvuma 1, 2A, 2B KM011252 KM011052 KM010848 KM010641 KM010463
80 Sporobolusmontanus (Hook. f.) Engl. Dusen 420 (US) Cameroon 1, 2A, 2B – KM011036 KM010829 KM010630 KM010447
81 Sporobolusmyrianthus Benth. Gereau 3491, Lovett & Kayombo (DSM) Tanzania, Mbeya 1, 2A, 2B KM011239 – KM010830 – KM010448
82 Sporobolusnatalensis (Steud.) T. Durand & Schinz Eddie 1141 (MEL) Australia, Queensland 1, 2A, 2B KM011240 KM011037 KM010831 KM010631 KM010449
83 Sporobolusnealleyi Vasey Peterson 17839, Valdes-Reyna & Hinton (US) Mexico, Nuevo León 1, 2A, 2B KM011242 KM011039 KM010833 KM010632 KM010450
84 Sporobolusnervosus Hochst. Wood 2021 (US) Yemen 1, 2A, 2B KM011245 KM011042 KM010836 KM010633 KM010453
85 Sporobolusniliacus (Fig. & De Not.) P.M. Peterson Moran 29081 (US) Mexico, Baja California 2A – – PV733879 – PV714804
86 Sporobolusnitens Stent Laegaard 15893 (US) Zimbabwe, Bulowayo 1, 2A, 2B KM011246 KM011043 KM010837 KM010634 KM010454
87 Sporobolusozarkanus Fernald Riggins 481 (US) USA, Texas 2B KM011247 KM011045 KM010840 KM010635 KM010456
88 Sporoboluspalmeri Scribn. Peterson 24862 & Romaschenko (US) Mexico, San Luis Potosí 1, 2A, 2B KM011248 KM011046 KM010841 KM010636 KM010457
89 Sporoboluspanicoides A. Rich. Smook 9865 (US) South Africa, Namibia 1, 2A, 2B – KM011050 KM010846 KM010640 KM010461
90 Sporoboluspectinellus Mez Fay 7131 (US) Central African Republic, Bamingui–Bangoran 1, 2A, 2B – KM011051 KM010847 – KM010462
91 Sporoboluspellucidus Hochst. Vesey-Fitzgerald 5226 (US) Tanzania, Arusha 1, 2A, 2B – KM011053 KM010849 – KM010464
92 Sporobolusphleoides Hack. Venturi 2039 (US) Argentina, Tucuman 1, 2A, 2B KM011253 KM011054 KM010850 – KM010465
93 Sporobolusphyllotrichus Hochst. Greenway 11844 & Kanuri (US) Tanzania, Arusha 1, 2A, 2B – KM011055 KM010851 – KM010466
94 Sporoboluspiliferus (Trin.) Kunth Peterson 24012, Soreng, Romaschenko & Abeid (US) Tanzania, Njombe 1, 2A, 2B KM011254 KM011056 KM010852 KM010642 KM010467
95 Sporoboluspinetorum Weakley & P.M. Peterson Peterson 14233, Weakley & LeBlond (US) USA, North Carolina 1, 2A, 2B KM011255 GU360358 GU359911 GU359506 GU359211
96 Sporoboluspseudairoides Parodi Wasum 2670 (US) Brazil, Parana 1, 2A, 2B KM011256 KM011057 KM010853 – KM010468
97 Sporoboluspumilus (L.) P.M. Peterson & Saarela Shchepanek 6426 & Dugal (CAN) Canada, Nova Scotia 1, 2A, 2B KM011148 KM010942 KM010721 KM010555 KM010349
98 Sporoboluspungens (Schreb.) Kunth Zohary 489 & Amdursky (US) Israel 1, 2A, 2B KM011257 KM011058 KM010854 KM010643 KM010470
99 Sporoboluspurpurascens (Sw.) Ham. Swallen 10179 (US) USA, Texas 1, 2A, 2B KM011259 KM011060 KM010856 KM010645 KM010472
100 Sporoboluspyramidalis P. Beauv. Peterson 24150, Soreng, Romaschenko & Abeid (US) Tanzania, Iringa 1, 2A, 2B KM011261 KM011062 KM010858 KM010646 KM010474
101 Sporoboluspyramidatus (Lam.) Hitchc. Peterson 18994, González-Elizondo, Carter, Rosen, Guaglianone & Torres Soto (US) Mexico, Durango 1, 2A, 2B KM011265 KM011065 KM010861 KM010648 KM010478
102 Sporobolusramigerus (F. Muell.) P.M. Peterson, Romasch. & R.L. Barrett Peterson 14338, Soreng & Rosenberg (US) 2A MK872671 – MK872424 – MK863099
103 Sporobolusramigerus (F. Muell.) P.M. Peterson, Romasch. & R.L. Barrett Peterson 14357, Soreng & Rosenberg (US) 2A MK872672 – MK872425 – MK863100
104 Sporobolusrigens (Trin.) Desv. Peterson 19224, Soreng, Salariado & Panizza (US) Argentina, Mendoza 1, 2A, 2B GU360627 GU360360 GU359909 GU359517 GU359213
105 Sporobolusrigidus (Buckley) P.M. Peterson Hatch 5738 & Bearden (US) USA, Colorado 1, 2A, 2B GU360548 GU360441 GU359880 GU359357 GU359300
106 Sporobolusrobustus Kunth Laegaard 17398, Goudiaby, Madsen, Sambou & Traore (US) Senegal, Kaolack 2A KM011268 KM011068 KM010864 KM010650 KM010481
107 Sporobolusruspolianus Chiov. McKinnon S91 (US) Somalia, Erigavo 2A KM011215 KM011010 KM010799 KM010613 KM010421
108 Sporobolussanguineus Rendle Gereau 6014, Mbago, Kayonbo & Lyanga (DSM) Tanzania, Kigoma 1, 2A, 2B KM011272 – KM010868 – KM010485
109 Sporobolusscabridus S.T. Blake Forster 20462 (MEL) Australia, Queensland 1, 2A, 2B KM011273 KM011071 KM010869 KM010652 KM010486
110 Sporobolusschoenoides (L.) P.M. Peterson Peterson 19814, Saarela & Sears (US) USA, California 2A GU360598 GU360455 GU359840 GU359361 GU359239
111 Sporobolussessilis B.K. Simon Senaratne E60951 & Armstrong (US) Australia, Queensland 1, 2A, 2B KM011274 KM011073 KM010871 KM010653 KM010488
112 Sporobolussilveanus Swallen Waller 3128 & Bauml (US) USA, Texas 1, 2A, 2B KM011275 KM011074 KM010872 – KM010489
113 Sporobolussomalensis Chiov. Hemming 2022 (US) Somalia 1, 2A, 2B – KM011076 KM010874 KM010655 KM010492
114 Sporobolusspartinus (Trin.) P.M. Peterson & Saarela Reeder 4568 & Reeder (US) Mexico, Coahuila 1, 2A, 2B KM011151 KM010945 KM010724 KM010558 KM010352
115 Sporobolusspicatus (Vahl) Kunth Peterson 24055, Soreng, Romaschenko & Abeid (US) Tanzania, Mbeya 2B KM011278 KM011079 KM010877 KM010658 KM010495
116 Sporobolusspiciformis Swallen Garcia 2638 (CIIDIR) Mexico, Durango 1, 2A, 2B KM011280 KM011081 KM010879 KM010660 KM010497
117 Sporobolussplendens Swallen King 1687 & Feddema (US) Mexico, Oxaca 1, 2A, 2B KM011282 KM011083 KM010881 KM010662 KM010499
118 Sporobolusstapfianus Gand. Laegaard 15939 (US) Zimbabwe 1, 2A, 2B KM011283 KM011084 KM010882 – KM010500
119 Sporobolusstolzii Mez Peterson 23946, Soreng, Romaschenko & Abeid (US) Tanzania, Ruvuma 1, 2A, 2B KM011284 KM011085 KM010883 KM010663 KM010501
120 Sporobolussubglobosus Stapf ex C.E. Hubb. Gambaga 581 (US) Ghana, Gambaga 1, 2A, 2B – KM011088 KM010885 – KM010504
121 Sporobolussubulatus Hack. Peterson 24317, Soreng, Romaschenko & Mbago (US) Tanzania, Arusha 2B KM011287 KM011089 KM010886 KM010666 KM010505
122 Sporobolustenellus (Spreng.) Kunth Smook 2874 (US) South Africa, Orange Free State 1, 2A, 2B – KM011090 KM010887 KM010667 KM010507
123 Sporobolustenuissimus (Mart. ex Schrank) Kuntze Peterson 9523 & Judziewicz (US) Ecuador, Pichincha 1, 2A, 2B KM011289 KM011091 KM010889 KM010669 KM010508
124 Sporobolusteretifolius R.M. Harper Peterson 14232, Weakley & LeBlond (US) USA, North Carolina 1, 2A, 2B GU360626 GU360376 GU359908 GU359509 GU359199
125 Sporobolustexanus Vasey Churchill 2645 & Kaul (US) USA, Nebraska 1, 2A, 2B KM011291 KM011093 KM010891 KM010671 KM010510
126 Sporobolus×townsendii (H. Groves & J. Groves) P.M. Peterson & Saarela Saarela 791 & Percy (UBC) Canada, British Columbia 1, 2A, 2B KM011126 KM010922 KM010699 KM010538 KM010329
127 Sporobolustourneuxii Coss. Adam 19416 (US) Mauritania 2B KM011292 KM011094 KM010892 KM010672 KM010511
128 Sporobolustrichodes Hitchc. Rzedowski 39901 (CIIDIR) Mexico, Michoacán 1, 2A, 2B KM011293 KM011095 KM010893 KM010673 KM010512
129 Sporobolusuniglumis Stent & J.M. Rattray Robinson 48 (US) Zambia 2B – KM011096 KM010894 – KM010513
130 Sporobolusvaginiflorus (Torr. ex A. Gray) Alph. Wood Wherry s.n. (US) USA, Pennsylvania 1, 2A, 2B KM011296 KM011099 KM010897 – KM010515
131 Sporobolusverdcourtii Napper Vesey-Fitzgerald 5336 (US) Kenya, Olagasale 2B KM011297 KM011100 KM010898 KM010674 KM010516
132 Sporobolusvirginicus (L.) Kunth Peterson 23820, Soreng, Romaschenko & Abeid (US) Tanzania, Lindi 1, 2A, 2B KM011299 KM011102 KM010900 – KM010518
133 Sporoboluswrightii Munro ex Scribn. Peterson 19841 & Lara-Contreras (US) Mexico, Coahuila 1, 2A, 2B GU360624 GU360348 GU359906 GU359511 GU359216
134 Urochondrasetulosa (Trin.) C.E. Hubb. Inckennon 181 (US) Somalia 1, 2A, 2B KM011307 KM011108 KM010908 KM010681 KM010526
135 Zoysiajaponica Steud. Kuragadake s.n. (US) Japan 1, 2A, 2B GU360643 – GU359923 GU359547 GU359196
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Citation

Peterson PM, Romaschenko K, Soreng RJ, Herrera Arrieta Y (2025) Reticulation within Sporobolus: recognition of two new sections, Acinifolii and Thellungia, and a new genus, Hyalolemma (Poaceae, Chloridoideae, Zoysieae, Sporobolinae). PhytoKeys 261: 99–123. https://doi.org/10.3897/phytokeys.261.157741

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Use of AI

No use of AI was reported.

Funding

We thank the Smithsonian Institution’s Restricted Endowment Fund, the Scholarly Studies Program, Research Opportunities, Atherton Seidell Foundation, Biodiversity Surveys and Inventories Program, Small Grants, and the National Geographic Society for Research and Exploration (Grant Nos. 8848-10, 8087-06).

Author contributions

All authors have contributed equally.

Author ORCIDs

Paul M. Peterson https://orcid.org/0000-0001-9405-5528

Konstantin Romaschenko https://orcid.org/0000-0002-7248-4193

Robert J. Soreng https://orcid.org/0000-0002-8358-4915

Yolanda Herrera Arrieta https://orcid.org/0000-0003-3814-6518

Data availability

All of the data that support the findings of this study are available in the main text.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

XML Treatment for Hyalolemma
phytokeys.261.157741-treatment1.xml (5.9KB, xml)
XML Treatment for Hyalolemma compactum
phytokeys.261.157741-treatment2.xml (3.7KB, xml)
XML Treatment for Hyalolemma somalensis
phytokeys.261.157741-treatment3.xml (4.4KB, xml)
XML Treatment for Sporobolus sect. Acinifolii P.M.Peterson, Romasch. & Soreng, sect. nov.
phytokeys.261.157741-treatment4.xml (6.2KB, xml)
XML Treatment for Sporobolus sect. Thellungia
phytokeys.261.157741-treatment5.xml (8.4KB, xml)
XML Treatment for Sporobolus collinus
phytokeys.261.157741-treatment6.xml (9.4KB, xml)

Data Availability Statement

All of the data that support the findings of this study are available in the main text.

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