Dombeya scorpioides Jourdain Fievet & Applequist, 2025

Fievet, Lucile Jourdain, Pechon, Timothee Le, Dubuisson, Jean-Yves & Applequist, Wendy, 2025, Dombeya scorpioides (Malvaceae: Dombeyoideae), a new species from southeastern Madagascar, Phytotaxa 704 (3), pp. 232-238 : 233-236

Dombeya scorpioides Jourdain Fievet & Applequist , sp. nov. ( Fig 1 )

Type:— MADAGASCAR. Atsimo-Atsinanana [Prov. Fianarantsoa], Farafangana, forêt de Manombo, 42 m, sur latérite, 27 Sept. 2002 (fl.), R. Rabevohitra, J. Rabenantoandro & R. Razakamalala 4121bis (holotype MO [barcode] 3515362!; isotypes P00862084 !, TEF n.v.) .

Diagnosis:— Dombeya scorpioides Jourdain Fievet & Applequist differs from D. oblongipetala Arènes (1958: 438) in its longer inflorescences with often scorpioid branches, broader petals, a stellate-hispid ovary, and a longer style.

Description:— Shrub 1–3 m tall; bark of large twigs pale brown with remnants of indument persisting. Young branches terete; becoming glabrous with age brown with dense indument of short, flattened megaradiate white stellate hairs with large centres. Stipules caducous or persistent, narrowly deltoid to narrowly lanceolate, 3.5–9.5 × 0.8–1.5 mm, with dense hairs like that of young twigs, acute. Leaves alternate, blade coriaceous, 7.0–17.7 × 2.3–5.4 cm, narrowly elliptical to elliptical with length normally over 2.5 × width (rarely broader, occasionally slightly lanceolate-, oblanceolate-, or oblong-elliptical); apex short-acuminate to long-cuspidate (acute, retuse); base narrowly rounded (sometimes minutely cordate at petiole juncture) to acute (or obtuse); margins entire, sometimes slightly crenate; camptodromous, one basal vein, the lateral weak; adaxial surface glabrate at maturity to pubescent with minute to very short flattish multiradiate stellate hairs; abaxial surface pubescent with minute to very short flattish multiradiate to megaradiate stellate hairs, densely pubescent on basal midrib; petiole short but with a blade ratio highly variable, terete, 6–40 mm, with dense indument like that of young twigs. Inflorescence cyme, erect, 10–22 cm long or more, including those in early anthesis, elongating after anthesis, 7–30-flowered; peduncle terete, 3.4–12.0 cm, usually bifurcate, occasionally without a basal division or trifurcate, usually with 1(–2) terminal flower(s), the branches scorpioid (most evident after flowering when branches are extended nearly straight but many flowers are already lost), occasionally with two flowers per node; pedicels 8–26 mm long, straight to slightly arcuate; pedicels and bracts densely pubescent with short megaradiate to multiradiate pale flattish stellate hairs and larger (to medium) tufted hairs, often darker centrally, the latter often absent from lower portion of inflorescence. Bracteoles caducous, elliptical to lanceolate (ligulate), 2.5–4.3 mm, with hair like that of pedicels. Flowers actinomorphic, 5(–3)-merous, pendant. Sepals narrowly lanceolate, 5.5–8.8 × 1.4–2.2 mm, rarely two sepals connate as an abnormality, white to pale green, abaxial surface moderately densely pubescent with indument similar to pedicels, the smaller stellate hairs minute to short, adaxial surface glabrous. Petals matte whitish to pink or light purple, broadly obovate to obdeltoid, 10.0–13.4 × 9.0–12.0 mm. Androecium glabrous, white, with basal corona very short, 0.2–0.3 mm with groups of 3 stamens alternating with staminodes; stamens 15, filaments 2.3–4.5 mm; anthers yellow, 0.85–1.20 mm, usually somewhat curved; staminodes 5, narrowly spatulate to ligulate, 3.5–6.5 mm. Gynoecium 3-carpellate, white; ovary superior, stellate-hispid with short (to minute) multiradiate to megaradiate hairs; style 2.5–3.0 mm, basally stellate-pubescent, apically glabrous; stigmas 3, 2.0– 2.5 mm, curled, glabrous. Seeds not seen.

Distribution, ecology, and habitat:—Collections are from a very restricted area in the southeastern region of Atsimo-Atsinanana, Madagascar ( Fig 2). Reported habitat is dense low-elevation (between 5 to 97 m elevation) humid forest near the coast, on lateritic soil. Flowers have been collected in June and post-flowering material with young fruits in September. The species is described as occasional.

Conservation status:—The three known gatherings of Dombeya scorpioides are from two localities very close together near the coast south of Farafangana, the forests of Manombo and Anambotaka. Using GeoCAT ( Bachman & Moat 2012), the Area of Occupancy (AOO) of the species is estimated at 8 km 2, with points in two adjacent grid cells; the Extent of Occurrence (EOO) cannot be calculated because only two points exist, so is set to equal the AOO. The two sites represent two locations with respect to the primary threat of forest cutting. One of the sites, Manombo, is a protected area, though it is in degraded condition due to past disturbances (including cyclone damage, another potential threat in this area) and introduced invasive species ( Goodman et al. 2018). The other, Anivorano, is not a protected area, and the label of Ludovic & Ratiana 404 and 405 describe the collection area as “Fortement perturbée par des exploitations (coupes)”, indicating that the forest was being cut; its condition has undoubtedly worsened since 2003. The IUCN (2022) guidelines support a preliminary estimate of the conservation status of the species as Endangered [EN B1ab(iii)+B2ab(iii)] based on its small AOO and EOO, two locations, and ongoing damage to the habitat in one location. Additionally, many botanical collections have been made in this area, so the small number of specimens suggests that the species is neither plentiful nor widespread.

Etymology:—The species is named for its distinctive cyme.

Taxonomic discussion:—The complex classification of Arènes (1958, 1959) separated two species of the tricarpellate D. subg. Xeropetalum into D. sect. Paracapricornua Arènes (1958: 359) due to their cymose inflorescences with scorpioid branching apically, whereas all other species had small umbels (D. sect. Decastemon) or non-scorpioid cymes with multiple orders of mostly dichotomous branching or with few flowers (D. sect. Xeropetalum (Delile) Planchon 1850: 225) or small umbels. The two species in D. sect. Paracapricornua, namely Dombeya borraginea Hochreutiner (1926: 62) and D. glaberrima Arènes (1958: 360) , had few similarities other than scorpioid inflorescences, and Applequist (unpubl. data) has observed that neither can be clearly distinguished from similar species placed in D. sect. Xeropetalum . Scorpioid branching may be inconsistent within species, or the character may become less obvious in older inflorescences or specimens in poor condition. Therefore, all of the scorpioid-branched species should be placed within D. sect. Xeropetalum , as presently recognized; though future phylogenetic studies may support the breakup of that group ( Skema 2012).

Using the classification and keys of Arènes (1959), Dombeya scorpioides would be placed in his D. subsect. Floribundae Arènes (1958: 436) (for very sparse leaf indument of small flat-stellate trichomes or long-fimbriate scales) “ser. Pilosae Arènes” (for hispid ovaries) subser. Dichotomae Arènes (1958: 446) (sepals [mostly] not reflexed after anthesis). “ Dombeya series Pilosae ” was not validly published because Arènes (1958, 1959) did not specify types for infrageneric groups, which was then a very new requirement, and in some cases, including this one, there was no species included whose epithet allowed it to be treated as the automatic type under Art. 10.8 of the International Code of Nomenclature ( Turland et al. 2018). The species in this series do not otherwise much resemble D. scorpioides : they are mostly broad-leaved, and the few with narrower (sometimes rather rhomboidal) leaves generally have conspicuously crenate or wavy leaf margins.

Dombeya scorpioides appears instead to have affinities to a group of species placed in D. subsect. Floribundae “ser. Epilosae Arènes”, another designation that was not validly published. Several of the species in that series have narrow leaves with entire margins. That series was characterized by having lepidote, rather than stellate ovaries, as do two narrow-leaved species previously described by Applequist (2009) that are affiliated with this group. However, indumentum is one of the characters that is conspicuously homoplasious in Malagasy Dombeya , and it is evident that transitions between stellate hairs and fimbriate scales were more easily and frequently made than Arènes recognized. The classification of D. sect. Xeropetalum is badly in need of revision, but we are not prepared to present an alternative at this time.

Within Dombeya “ser. Epilosae”, D. scorpioides may resemble other narrow-leaved species, including D. floribunda Baker (1884: 325) , D. gracilicyma Arènes (1958: 443) , D. oblongifolia Arènes (1958: 438) , D. oblongipetala Arènes (1958: 443) , D. rienanensis Applequist (2009: 291) , D. sahatavyensis Arènes (1958: 441) , D. trohy Arènes (1958: 444) , and D. asymmetrica Applequist (2009: 289) . It is not yet clear whether all of those species ought to be recognized as distinct at the species level (Applequist, unpubl. data). Regardless, the material of D. scorpioides is not identifiable with any of the existing species as presently circumscribed. None of those species have been reported to have noticeably scorpioid inflorescence branching or stellate ovaries. The leaf shape, size, and often short-acuminate leaf apex of D. scorpioides would be unusual in any other species, though potentially found as an uncommon variant. In addition, all of the existing species have other reproductive or vegetative characters that distinguish them from D. scorpioides ; for example, some have proportionately much narrower petals. Dombeya oblongipetala was chosen as the comparator for D. scorpioides because the type was collected between Befotaka (inland) and Farafangana, so it might be found in the same area.

Additional specimens examined:— MADAGASCAR. Atsimo-Atsinanana [Prov. Fianarantsoa]: Farafangana, commune Arkarana, fok. Anivorano, env. 9 km à l’ouest du village Anivorano, forêt d’Anambotaka, 93 m, 10 June 2003, Ludovic & Ratiana 404 ( MO [barcode] 3515361!, TAN image!), Ludovic & Ratiana 405 ( MO [barcode] 3515363!, TAN image!).

Figures

FIGURE 1. Morphological features of Dombeya scorpioides. A. Habit. B, C. Flower. D. Flower bud. E. Gynoecium. F. Part of the androecium. G. Petal. H. Sepal, adaxial face. I. Sepal, abaxial face, with zoom on the hairs on the left. Drawn from Rabevohitra et al. 4121bis (P). Illustration by Ludivine Lougou, January 2025.