Twisted stems and tiny cyathia. Recognizing Indian succulent spurges

Resemblance at a distance

Twisted, fleshy stems with spiny margins create the distinctive habit of Euphorbia tortilis. In southern India, similar plants were identified for many years largely through this conspicuous feature. Close examination nevertheless revealed differences in stem-segment width, wing number and the structure of small reproductive organs. Two papers published descriptions of Euphorbia costatoalata, Euphorbia sankarensis, Euphorbia bahalita and the botanical variety Euphorbia tortilis var. mysorensis. Each taxon was defined through a combination of characters that can be checked again on specimens [De Jong et al. 2026] [Naidu and Kusom 2026].

The first study appeared online in 2025 and was assigned to the journal volume for 2026. The second, also from 2026, extended the comparison to additional plants resembling E. tortilis. Both papers move from field observation to a taxonomic diagnosis, a description of differences that distinguish a new taxon from known ones. Their shared subject is recognition of boundaries through morphology. The evidence encompasses the outline of the adult plant as well as details that require dissection under a microscope [De Jong et al. 2026] [Naidu and Kusom 2026].

Specimens, names and comparison in a garden

The description of E. costatoalata began with photographs of plants showing pronounced stem ribbing near Kolar and on the rocky Savandurga massif. De Jong and colleagues collected material, examined herbarium specimens and compared it with E. tortilis plants from several places in Tamil Nadu. The neotype of the latter name, held at herbarium MH, played a particular role. A nomenclatural type provides a reference for applying a name. It connects comparison of the new plants with a specific specimen representing the previously recognized species [De Jong et al. 2026].

Some plants from different localities were grown beside one another in an experimental garden. Fresh material was collected in different seasons to examine leaves, cyathia and mature fruits. In the second paper, Naidu and Kusom used plants raised from cuttings collected in 2006–2008 and maintained in the biodiversity conservation garden at Dharmavana Nature Ark. They collected twigs again at the localities during flowering and fruiting in 2023–2025. This material allows field characters to be compared with organs developing in a living collection [De Jong et al. 2026] [Naidu and Kusom 2026].

Wings, twisting and ribbing

Wings are the projecting longitudinal edges of the succulent stem. In E. costatoalata, the authors counted three to five. Additional ribbing between them forms a characteristic pattern resembling a fish skeleton. Typical E. tortilis in De Jong’s comparison usually had three wings, occasionally four, and surfaces between them that generally lacked such pronounced ribbing. The ranges of wing number partly overlap. The presence of four edges alone therefore does not settle an identification [De Jong et al. 2026].

The arrangement of stem segments across the crown also matters. In E. costatoalata, they are usually straight or slightly twisted, leaving the crown open and irregular. E. tortilis forms a more compact arrangement of strongly spiralled segments. De Jong and colleagues also found variation in the prominence of ribbing among populations of the new species. It was strongest in the type population. This variation supports comparison of several organs together. Fainter ribs in a particular specimen can be assessed alongside its inflorescences, fruits and seeds [De Jong et al. 2026].

A cyathium viewed from two directions

A cyathium is a small inflorescence in which highly reduced flowers sit within a shared involucre. A bisexual cyathium contains male flowers and a female flower. Glands occur along the rim of the involucre, and their outlines and profiles can be compared under magnification. These details distinguish some otherwise similar spurges. In E. costatoalata, the glands are oval to trapezoidal and distinctly convex in side view. In the E. tortilis material examined, they are oblong with a flat upper surface. Looking only from above therefore overlooks one of the diagnostic characters [De Jong et al. 2026] [Naidu and Kusom 2026].

Further differences concern the styles, which end in surfaces that receive pollen. In De Jong’s comparison, the styles of E. tortilis were united along their lower third, whereas those of E. costatoalata were free from the base. This character is examined in an adequately exposed female flower. The external outline of a flowering twig does not show it in sufficient detail. Combining gland profile, the extent of style fusion and stem structure produces a more detailed diagnosis than a single conspicuous feature of habit [De Jong et al. 2026].

Two new species with short stem segments

E. sankarensis grows among granite rocks on the slopes and summit of Sankari Hill. Its stems are three-angled and seldom distinctly twisted, with segments 5–8 cm long. Glands have a fan-shaped outline in male cyathia, whereas those in bisexual cyathia were described as elliptic. Distinguishing these two kinds of inflorescence makes the comparison consistent. Two differently shaped glands can belong to the same species if they developed in structurally different cyathia. In this plant, the styles are united to the middle of their length [Naidu and Kusom 2026].

E. bahalita has a different, low and compact habit. Its lateral branches are decumbent, and twisted stem segments reach 4–8 cm in length. It was described from the T. Kallupatti area and the foot of Sankari Hill. It produces male and bisexual cyathia with an involucre narrowing towards the base and broadly oblong glands. The styles remain free from the base. Similar segment lengths in the two new species therefore occur alongside different whole-plant and reproductive characters that allow them to be distinguished [Naidu and Kusom 2026].

Capsules and seeds complete the diagnosis

Fruit provides characters that are unavailable on a plant examined before flowering. In E. costatoalata, the three-lobed capsule has rounded corners and a concave upper surface. Its seeds are dark brown with paler streaks and speckles. De Jong and colleagues compared them with the slate-grey seeds of the E. tortilis plants examined. They also described a difference apparent earlier in development. Seedlings of E. costatoalata had mottled surfaces between their wings, whereas such markings were not observed in seedlings of E. tortilis [De Jong et al. 2026].

In the second paper, E. sankarensis was distinguished by almost globose fruits with weak dorsal ridges and a concave upper surface. In E. bahalita, capsules were three-angled, convex above and recurved downwards. Its seeds ranged from approximately quadrangular to ovate in outline and bore a small caruncle, an outgrowth of the seed coat. The comparative table described seeds of E. sankarensis as lacking this outgrowth. In these studies, the caruncle serves as an identification character. Any role in dispersal would require separate observations [Naidu and Kusom 2026].

A botanical variety within a species

The third taxon described by Naidu and Kusom was assigned the rank of botanical variety. E. tortilis var. mysorensis comes from the Nanjangud area in Mysore District and develops broad, twisted, ribbed stems with three to five angles. The description gives a segment diameter of 10–12 cm. Cyathial glands are obovate to oblong with wavy margins. The styles remain free from the base. The authors considered this combination sufficient to recognize a variety within E. tortilis [Naidu and Kusom 2026].

The rank of botanical variety describes a taxonomic subdivision below the species. It is distinct from a cultivar name applied to a selected plant in horticulture. The authors observed E. tortilis var. mysorensis along field bunds and in boundary fences. These records concern a landscape used by people, so they cannot alone reconstruct the variety’s original habitat. Specimen provenance remains important both when interpreting its occurrence and when comparing material from additional collections [Naidu and Kusom 2026].

Distribution and the limits of inference

De Jong and colleagues suggested that E. costatoalata probably replaces E. tortilis north of the Nilgiri and Biligirirangan ranges. They presented this as an impression from observations available so far. A small group of similar plants in a fence line south of those hills left questions about the locality’s origin and possible contact between the two species. The study did not establish whether hybridization occurs there. A locality map helps formulate such questions, while resolving them requires further field evidence and reproductive studies [De Jong et al. 2026].

Both publications document morphological distinctness and identify type specimens that can be revisited in later comparisons. They provide no DNA sequencing of the new taxa, tests of reproductive isolation or estimates of their divergence dates. Observing plants in a garden improves access to their organs, but the reported methods do not constitute an experiment measuring how a specific environmental factor affects shape. At this stage, the best documented result is the combination of described diagnostic characters. It provides the starting point for further assessment of species boundaries [De Jong et al. 2026] [Naidu and Kusom 2026].

From identification to conservation of localities

Accurate identification changes how occurrence data are assigned. A specimen labelled E. tortilis that matches the diagnosis of E. costatoalata after re-examination documents a locality of another species. This does not make the names synonyms. It changes the identification of particular material. Similarly, the number of individuals observed in one population does not automatically represent the taxon’s total abundance. Naidu and Kusom recorded more than 240 E. sankarensis plants and approximately 58 plants in the type population of E. bahalita. These are local field records [De Jong et al. 2026] [Naidu and Kusom 2026].

For E. costatoalata, the authors proposed Data Deficient because populations remain incompletely known. They also described plants being destroyed by development on small hillocks. This information connects species identification with a specific process altering its localities. Further observations should retain an identification checked through several organs together with the material’s provenance. Documentation of stems, cyathia, mature capsules and seeds allows a new record to be compared with the diagnosis. It also makes an older identification open to correction when fuller evidence becomes available [De Jong et al. 2026] [Naidu and Kusom 2026].

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