Alternanthera indica S.Arya, V.S.A.Kumar

Arya, Sindhu, Iamonico, Duilio, Pino, Ivonne Sánchez-Del & Kumar, Venugopalan Nair Saradamma Anil, 2021, Alternanthera indica (Amaranthaceae), a new species from Kerala (India), Phytotaxa 482 (2), pp. 191-196 : 192-195

Alternanthera indica S.Arya, V.S.A.Kumar , Sánchez-del Pino & Iamonico, sp. nov. ( Figs. 1–2 ).

Type: — INDIA: Kerala, Thiruvananthapuram district, Palode, way to Kulathupuzha , 110 m, 8.97° N, 77.3°E, 16 December 2018, Anil Kumar & Arya s. n. (holotype: TBGT!, isotypes; CMPR!, HFLA!)

Description ( Figs. 1–2 ): —Annual herb, 80–100 cm tall. Stem prostrate to ascending (sometimes rooted at the nodes), ribbed, green, glabrous or sparsely pubescent, branched, with prominent nodes. Leaves simple, not fleshy, opposite, blade spathulate, 5.5–7.5 × 1.5–2 cm, dark-green, pubescent, with margin entire and ciliate, base cuneate, apex obtusetruncate to emarginate, mucronate; petiolate (petiole 2–3.5 × 1–2 mm, glabrous). Synflorescence arranged in sessile and axillary glomerules, 5–6 glomerules per node. Bracts whitish-green, linear, 0.6–0.8 × 1–1.2 mm, shorter than sepals; bracteoles slender, trasparent, minute (<0.5 mm wide, <1 mm long). Flowers bisexual, 9–12 per glomerule. Five sepals ovate, 2–2.5 × 1–1.5 mm, slightly unequal (the outer sepals about 1 mm shorter than the inner ones), often recurved at the tip, strongly pubescent on the dorsal surface (trichomes simple, acicular-tipped), margins thinner than the central zone and entire, apex acute, mucronate; veins 6–8, relatively parallel, extending from the base to the apex, unbranched. Stamens 5, 1.2 mm long (filaments about 0.5 mm long, anthers about 0.7 mm long), raising from androecial cup and alternating with the appendages of the androecial tube; appendages equal or longer than stamens and laciniate; gynoecium 0.5–0.7 mm long, style 0.2–0.3 mm long, stigma capitate, glandular. Fruit (utricle), obovoid, about 1 mm long, slightly wrinkled at the base, smooth elsewhere. Seeds globose-ellipsoidal, 0.6 × 0.8 mm, black, smooth.

Etymology: —The epithet refers to the native area ( India).

Phenology: —Flowering and fruiting times August–January.

Distribution and ecology: —The species occurs in moist waste lands near temporary streams, pools or river and in moist evergreen forest areas of Kulathupuzha (Kollam District), and Bonacaud (Thiruvanathapuram District).

Conservation Status: —On the basis of the IUCN Red List criteria ( IUCN 2019) and the available data, we can apply the criteria B and C. By both the application of criterion B2 [AOO is less than 1 km 2 (941.3 m 2)] and C2ai (a total of 45 individuals were counted), Alternanthera indica can be assessed as Critical Endangered (CR).

Taxonomic notes: — Alternanthera indica is similar to A. carcasana Kunth (1817: 205) , A. paronychioides Saint- Hilaire (1833: 439–441) var. robusta Chodat (1903: 355) [= A. paronychioides subsp. chacoensis Pedersen (2016: 314) , see also Ramella 2016], A. pungens Kunth (1817: 206) , A. sessilis ( Linnaeus 1753: 225) Brown (1810: 417) , and A. tenella Moquin-Tandon (1849: 355) sharing sessile synflorescences and habit. However, the new species differs from these mentioned species in various vegetative and sexual features (see Table 1). The ratio length/width of the leaves is 2.0– 2.5 in A. indica , whereas in the other species is up to 2 ( A. paronychioides var. robusta ), 3–5 ( A. carcasana and A. tenella ), or 5–7 ( A. pungens ). Also the apex of the leaves is different (obtuse-truncate to emarginated in A. indica vs. acute or obtuse and never emarginated in A. carcasana , A. paronychioides var. robusta , A. pungens , A. sessilis and A. tenella ). Bracteoles of A. indica are minute and shorter than those occurring in the other species (<0.5 mm wide, <1 mm long). Sepals of A. indica (2–2.5 mm) are shorter than those of A. carcasana and A. paronychioides var. robusta (3–5 mm), A. pungens (5–7 mm), and A. tenella (3–4.5 mm), whereas A. sessilis displays similar length (2–3.5 mm). The ratio length of sepals / length of appendages of the androecial tube is 4 (2:0.05) in A. indica , i.e. much higher than in the other species (up to 2.5 for A. paronychioides ) (see Table 1).

On the basis of unpublished molecular data (Arya et al. in prep.), Alternanthera indica is recognizable as a new species belonging to the subgen. Alternanthera , based on the shape of the inflorescence (globose and condensed) and the stigma (capitate) (see Sánchez-del Pino & Iamonico 2016). Two of the species most resembled species of Alternanthera indica , i.e. A. caracasana and A. pungens , based on a phylogenetic analysis conducted with cpDNA using trnL-F and rpl16, resulted in a single clade (Sánchez-del Pino et al. 2012). Whereas, A. tenella —resembled A. indica as well — results in a different clade with other American species (Sánchez-del Pino et al. 2012). Unfortunately, a molecular analysis to update the taxonomy of Alternanthera is still in progress and species from its range of distribution will be required to get a wide and better representation of the genus. Up to now, any debate trying to explain a possible origin of the new species remains unclear.

Additional specimens examined (paratypes):— INDIA. Kerala, Thiruvananthapuram District, Vithura, 16 m, 26 January 2019, Anil Kumar & Arya 16523 (TBGT); Kollam District, Kulathupuzha, 8 m, 30 August 2019, Anil Kumar & Arya 83425 (CMPR).

Figures

FIGURE 1. Alternanthera indica. A) habit; B) synflorescence; C) glomerule; D) sepal (dorsal view); E) stamens and appendages on the androecial tube; F) pistil.

FIGURE 2. Alternanthera indica.A) habit; B) glomerule; C) opened flower;D) sepal (dorsal view); E) flower without sepals; F) appendage on the androecial tube; G) stamens.