Impatiens alboarenicola Y.Fujimoto, Rabarison & Tagane

Fujimoto, Yutaro, Tagane, Shuichiro, Rabarison, Harison, Andriamahasetra, Rova N., Komada, Natsuki & Kitajima, Kaoru, 2024, Impatiens alboarenicola, a new species of Balsaminaceae from north-western Madagascar, Phytotaxa 650 (3), pp. 206-212 : 207-208

Impatiens alboarenicola Y.Fujimoto, Rabarison & Tagane , sp. nov. ( Figs 2 & 3 )

TYPE:— MADAGASCAR. Boeny Region : Marovoay District, Ankarafantsika National Park, 16.31722°S, 46.81053°E, 152 m elev., 20 February 2023, S. Tagane & H. Rabarison A261 (holotype DBEV!; isotypes KAG [ KAG184161 !], TAN!) .

Diagnosis:— Impatiens alboarenicola is similar to I. barthlottii Fischer & Rahelivololona (2007a: 272) of Madagascar in leaf and flower shape, but clearly distinguished from it by its shorter stature of 5.3–18.5 cm tall (vs. 20–70 cm tall in I. barthlottii ), absence of a tuber at the stem base (vs. presence, with elongate tuber), solitary (rarely 2) flowers in the axils of leaves (vs. with 2 flowers), and smaller light purple to pale purple flowers of 1.3–1.8 cm long (vs. white, 2.3–2.5 cm long). It is also similar to I. tsingycola Fischer & Rahelivololona (2007a: 274) of Madagascar in its short stature, leaf shape, and petal colour, but different in having smaller leaf blades (7–)16–41(–64) mm long (vs. 55–81 mm long in I. tsingycola ), (1–)7–9(–11) pairs of teeth on the dentate leaf margin (vs. 15–21 pairs), solitary (rarely 2) flowers in the axils of leaves (vs. 2–3 flowers), and saccate spur-like projection located at ca. 5 mm below the apex of the lower petal lobe of the lateral united petals (vs. at the apex of the lower petal lobe).

Annual herb, 5.3–18.5 cm tall, glabrous except adaxial surface of lamina. Stems erect, succulent, pale brown to reddish-brown in vivo, often dark blue to dark purple in sicco, not branched or rarely branched, without tuber at base. Leaves alternate, petiolate; petiole pale brown to reddish-brown, (7.5–)12–20(–46) mm long, with extrafloral nectaries; lamina ovate-triangular, ovate, elliptic-ovate, (7–)16–41(–64) × (4–)10–27(–43) mm, adaxial surface covered with short white hairs, abaxial surface glabrous, apex acute, base cuneate to acute, slightly decurrent, margin dentate, teeth (1–)7–9(–11) on each side, with gland-tipped appendages, secondary veins (3–)4–6(–8) pairs, tertiary veins indistinct on both surfaces. Flowers light purple to pale purple with yellow spots on lateral united petals and with spur, 1.3–1.8 cm long. Pedicels 18–25 mm long. Bracts narrowly triangular, 0.9 × 0.5 mm, apex acute. Lateral sepals 2, lanceolate, 2.5–3.0 × 0.5–1.0 mm, apiculate, shallowly cucullate. Lower sepal navicular, 8 × 3 mm, apex acuminate, spur obtuse, 4.0– 4.5 mm long, strongly curved. Dorsal petal cucullate, 5.0–6.5 × 2.5–4.5 mm, apex rounded to emarginate, often with apicule 0.5 mm long. Lateral united petals 10–13 mm long, upper petal lobe rounded, 4.5–6.5 × 2.0– 3.5 mm, lower petal lobe suborbicular, 10–13 × 3.5–5.0 mm, with yellow, 1 mm long, saccate spur-like projection at ca. 5 mm below apex. Anthers ca. 2 mm long. Ovary 1.5 mm long, light greenish-yellow in vivo, style cone-shaped, 0.2 mm long, stigma acute. Fruits fusiform, 3.0–7.5 × 1.0– 2.5 mm, slightly recurved, green in vivo. Seeds 12 per capsule, ellipsoid, 1–2 mm long, brown to yellowish-brown, apex acute.

Other specimens examined: — MADAGASCAR. Boeny Region : Marovoay District, Ankarafantsika National Park, 16.32035°S, 46.81037°E, 175 m elev., 18 February 2023, with flowers, S. Tagane et al. A190 ( DBEV, KAG [ KAG184090 ], TAN) ; ibid., 16.32048°S, 46.81055°E, 22 March 2023, with flowers, Y. Fujimoto A339 ( DBEV) ; ibid., 16.32048°S, 46.81055°E, 27 March 2023, with flowers in a spirit collection and fruits, Y. Fujimoto A340 ( DBEV) .

Distribution: — Madagascar (thus far known only from Ankarafantsika National Park) ( Fig. 1 ).

Habitat: —In the semi-shaded understory of seasonally dry tropical forest on white sand, 140–200 m elev. The forests are dominated by Baudouinia fluggeiformis Baillon (1868: 201) , Bussea perrieri Viguier (1949: 355) , Dalbergia greveana Baillon (1884: 436) ( Fabaceae ), Drypetes perrieri Leandri (1939: 194) ( Putranjivaceae ), Noronhia alleizettei Dubard (1907: 551) ( Oleaceae ), Cassipourea lanceolata Tulasne (1856: 121) ( Rhizophoraceae ), Rhopalocarpus similis Hemsley (1903 : t. 2774) ( Sphaerosepalaceae ), and Pyrostria ampijoroensis ( Arènes 1960: 24) Razafimandimbison et al. (2007: 519) ( Rubiaceae ) ( Fujimoto et al. 2024).

Phenology: —Flowering at the end of February to March, fruiting in March.

Etymology: —The epithet alboarenicola refers to the white sand habitat of the new species.

Vernacular name: — Kivolanala kely or rangy kely, suggested here. Kivolanala and rangy in Madagascar refer to Impatiens species. Kely means small, referring to the plant size of I. alboarenicola .

Preliminary conservation assessment: —Critically Endangered (CR). Impatiens alboarenicola is known from a single location, Jardin Botanique A of the Ankarafantsika National Park. The number of mature individuals is estimated fewer than 50. It is likely to have more subpopulations in the region, but a large area of seasonally dry tropical forests around Ankarafantsika has disappeared ( Schüssler et al. 2023). The present habitat is within the protected area of the national park. However, forest fires have often occurred, which might gradually reduce the habitat of I. alboarenicola . Given this situation, it is assessed as CR, according to the IUCN criterion D ( IUCN 2012).

Note: — Impatiens alboarenicola is morphologically classified into the Impatiens subgen. Impatiens sensu Fischer and Rahelivololona (2002) because of the lower sepal with a spur and the petiole with extrafloral nectaries ( Fischer & Rahelivololona 2007a, b). Within the I. subgen. Impatiens , I. alboarenicola belongs to the section Uniflorae Hooker & Thomson (1859: 113) , based on its short-fusiform capsules, conspicuously turgid at the middle, and fascicled inflorescence with 1 to 2 flowers ( Yu et al. 2016). However, recent molecular phylogenetic analyses based on nuclear and plastid markers demonstrated that the species of Malagasy I. subgen. Impatiens was not a monophyletic group ( Rahelivololona et al. 2018). Further analysis including I. alboarenicola is necessary to clarify its phylogenetic and taxonomic position.

Figures

FIGURE 1. Location of Ankarafantsika National Park.

FIGURE 2. Impatiens alboarenicola Y.Fujimoto, Rabarison & Tagane.A. Habitat. B. Habit. C. Entire plant body. D. Adaxial leaf surface. E. Hairs on an adaxial leaf surface. F.Abaxial leaf surface. G. Flower buds. H. Bract. I. Flower (front view, male stage). J. Flower (lateral view). K. Lateral sepals. L. Lower sepal with spur (lateral view). M. Lateral united petal (lateral view). N. Ovary. O. Fruits. P. Seeds. Photos: A and F–H from S. Tagane et al. A261; B from S. Tagane et al. A190; D from Y. Fujimoto A339; C, E, and I–P from Y. Fujimoto A340. Scale bars: C = 5 cm; I, J, and O = 5 mm; H, K–N, and P = 2 mm. Photographed by S. Tagane (A, B, and F–H), Y. Fujimoto (C–E and I–O), and W. Noyori (P).

FIGURE 3. Isotype of Impatiens alboarenicola Y.Fujimoto, Rabarison & Tagane (KAG184161).