Amaranthus rajasekharii S.Arya, V.S.A.Kumar, W.K.Vishnu & Iamonico, 2020

Arya, Sindhu, Kumar, Venugopalan Nair Saradamma Anil, Vishnu, Walsan Kalarikkal & Iamonico, Duilio, 2020, Amaranthus rajasekharii (Amaranthaceae), a new species from Kerala (SW-India), Phytotaxa 433 (2), pp. 153-160 : 154-156

Amaranthus rajasekharii S.Arya, V.S.A.Kumar, W.K.Vishnu & Iamonico , sp. nov. ( Fig. 1a–i )

Type: — INDIA. Kerala: Thiruvananthapuram district, Palode, way to Kulathupuzha, 110 m, 8.97 ° N, 77.3 ° E, 4 February 2018, Anil Kumar & Arya s.n. (holotype TBGT!, isotypes CMPR!, HFLA!).

Diagnosis: — Amaranthus rajasekharii is morphologically similar to A. dubius Martius ex Thellung (1912: 203) , from which it differs ( Table 1) in having the stem reddish to purple (vs. green in A. dubius ), bracts linear and very reduced (0.08–0.1 mm) (vs. ovato-deltoid, 1.3–1.7 mm), tepals of pistillate flowers ovate to lanceolate (vs. oblong-spatulate), gynoecium whitish (vs. green), marginal zone of seeds with clear reticulate ornamentation (vs. very slightly reticulate), pollen grain surface with 21–23 pores (vs. 27–30), 3–5 ektexinous bodies (vs. mostly 3), and margin of pores not depressed and without conspicuous ornamentation (vs. clearly depressed and with conspicuous ornamentation) ( Fig. 2 ).

Description (macromorphology): —Monoecious annual herb, 100–130 cm tall. Stem erect to ascending, angular, reddish to purple, glabrous or sparsely pubescent, branched (branches sometimes ribbed). Leaves simple, alternate, petiolate (petiole terete, sparsley pubescent, 4–9 cm long), blade ovate to lanceolate, 2.5–10.4 × 1.5–6.5 cm, darkgreen, with margin undulate, base attenuate, apex obtuse or slightly emarginated, sparsely pubescent on the abaxial surface. Synflorescence arranged in terminal, 15–20 cm long and slender spikes (one per branch), each one composed by more or less spaced glomerules of 4–8 flowers; axes of each synflorescence terete, purple or green, sparsely pubescent. Bracts 0.08–0.1 mm, linear-subulate, glabrous, green, with apex spinescent. Flowers unisexual, yellowishgreen. Staminate flowers (diameter about 5 mm) occurring in the basal and middle part of the synflorescences; tepals 5, equal, ovate, acute, 0.7–1.9 mm long; stamens 4; androecium 3 mm long, anthers sagittate. Pistillate flowers (diameter about 3 mm) occurring throughout the synfloresence; tepals 5, equal, ovate to lanceolate, acute, 1.5–2 mm long slightly keeled (keel green); ovary 1–2-celled, glabrous, with 1 ovule; stigmas 3. Fruit ovate, as long as the perianth (1.2–2.2 × 1.1–1.6 mm), irregularly dehiscent or indehiscent. Seed one per fruit, discoidal (diameter ca. 0.9–1 mm).

Description (micromorphology): — Seed surfaces sculpured in the marginal zone (epidermal cells ornamentation reticulate, each cell being subquadrangular), smooth in the central zone. Pollen grains spheroidal, polypantoporate, each one with 21–23 pores; ektexinous bodies number 3–5, rarely fused, often obscure; surface ornamentation mamillate, sparse, margin of pores not depressed and without conspicuous ornamentations.

Etymology: —The species is honoured to Narayana Pillai Rajasekhar, father of the first author (SA), who is a traditional medicine pratictioner and is much fond of local plants and their uses.

Phenology: —Flowering and fruiting times in February–August.

Habitat: —The species occurs in dry waste lands and in the mixed forest outskirts of Palode-Kulathupuzha- Thenkasi range.

Distribution: —Uloor (Thiruvananthapuram district), northern Payyanur ( Kannur district), southern Kaloor (Ernakulam district), South-eastern Vellakinar (Alapuzha district) (Fig. 4.).

Taxonomic notes: —According to Mosyakin & Robertson (1996) Amaranthus rajasekharii belongs to the subgen. Amaranthus since it was a the monoecious species with 5 tepals in pistillate flowers and having a terminal synflorescence. At sectional level our new proposed species could be placed in the sect. Amaranthus subsect. Hybrida Mosyakin & K.R.Robertson (1996: 278) . However, A. rajasekharii is morphologically similar to A. dubius which was placed by Mosyakin & Robertson (1996) in another section, i.e. the nothosect. Dubia Mosyakin & K.R.Robertson (1996: 278) . The correct placement in Amaranthus of A. rajasekharii remains obscure and further molecular studies on the whole monoecious amarants are necessary.

The main characters shared by Amaranthus rajasekharii and A. dubius are: hairness of the stem (glabrous of sparsely pubescent), arrangement of the synflorescences (like-panicle structures), bracts of the pistillate flower (which are shorter that the tepals), and number of tepals in the pistillate flowers (5). On the other hand, various features are clearly different (see Table 1) and they were verified to be constant on the basis of the cultivation tests (after about a week sprouting came up and the flowering stage started after 45 days). In addition, we noted that the staminate flowers are always placed in the middle and basal part of the terminal synflorescence in A. rajasekharii , whereas they occur in the distal part in A. dubius . Moreover, although the characters of staminate flower have not an high taxonomic value in Amaranthus (but see Mosyakin & Robertson 2003), we observed that the ratio between the number of staminate and pistillate flowers is about 1: 100 in A. rajasekharii while it is 1: 10 in A. dubius .

Finally, as concerns the chorology of the two species, Amaranthus rajasekharii is probably endemic to Kerala region. On the other hand, A. dubius is a species native to tropical regions of America and rarely introduced in Europe and Asia (see Bojian et al. 2003, Masyakin & Robertson 2003, Bayón 2015). The two species appear to be allopatric.

Note on the conservation status: —Since Amaranthus rajasekharii could occur in further sites in SW-India (and India at all), we think that further conservation data are required. As a consequence, the new species is here assessed as DD (Deficient Data) according to the IUCN criteria ( IUCN 2012).

Additional selected specimens:— Amaranthus rajasekharii (paratypes). INDIA. Kerala: Thiruvananthapuram District, Uloor to Kesavadasapuram , 18 m, 27 May 2018, Anil Kumar & Arya s. n. (TBGT), Kollam District , Kollam town , 8 m a.s.l., 30 May 2018, Anil Kumar & Arya 87295 (CMPR). Ernakulan District , Ernakulam –Thevara route, 4 m, 9.9312° N 76.2673° E, 3 January 2019, Anil Kumar & Arya 87312 (CMPR) ; Alappuzha District, Cherthala –Alappuzha region, 11m, 9.4981° N 76.3388° E, 20 February 2019, Anil Kumar & Arya 87365 (TBGT) .

Amaranthus dubius . BAHAMAS. Exuma, Great Guana Cay, Exuma Chain, 22 February 1905, Britton & Millspaugh 2910 (NY01373943!). BELIZE. Orange Walk Distr., 100 m S of San Antonio village, Square 24P., 27 December 1976, leg. Puleston 7643 (USF236113!, det. Dwyer in 1977); Caye Caulker (southern island), village of Caye Caulker, 8 March 2008, Rietsema 43408 (NY01158561!). BRAZIL. Município de Barra do Corda, ca. 1 km South of center of city at “Sitio dos Ingleses” school grounds, on East slope of Rio Corda River valley, waste ground by buildings, 15 January 1970, Eiten & Eiten 10304 (K001207041!); Município de Loreto, 2 km SE of Loreto, South of Rio Balsas at ferry point, open weedy banana groove, 150 m a.s.l., 31 January 1970, Eiten & Eiten 10415 (K001207040!). DOMINICAN REPUBLIC. St. Paul, Rodney’s Rock, Hertford Estate. Carribean Coast, Coastal Highway. 0.5 km SE of rock, 13 December 1993, Bradshaw & Renne 25416 ( US 01084419!); St. Paul, disturbed areas around Brizee’s Market, Canefield, W coast, 50 ft, 24 February 1997, Hill & Phillippe 28906 (USF288828!). GREAT BRITAIN (Cayman Islands). Grand Cayman Island. Agriculture office, Georgetown, 17 August 1971, Chevalier 80 (USF139929!). GUYANA. Barima-Waini, in Shell Beach Sea Turtle Monitoring Camp, about 5 mi. South-east of Waini Point, 8 November 1998, Hollowell et al. 259a ( US 00752210!). HAITI. Nord-Óuest, Île de la Tortue, Vicinity of La Vallée, Tortue Island. La Vallée Valley, 2 January 1929, Leonard & Leonard 11454 ( US 00847527!). HAWAII. Oahu, Kaneohe, 20 October 1930, Wilder & Neal s.n. (P05251963!); Honolulu, Manoa Valley, 16 May 1933, Krauss s.n. ( US 00453041!). MADAGASCAR. Tanala, Fort-Carnot, 1986, Beaujard 8 (P05159968!). REPUBLIC OF THE MARSHALL ISLANDS. Bikini Atoll, Bikini Islet, near middle, lagoon side, in weedy ground around old houses, 12 November 1985, Fosberg 65172 (P05251962!). ST. LUCIA. Castries, 4 April 1958, Proctor 17526 ( US 01084431!). TANZANIA. Mlupa, 13 October 1932, Geilinger 3011 (K000190113!). TRINIDAD AND TOBAGO. Hort. Trinidad, 1889, s.c. 3398 ( US 1099934!). UGANDA. Masaka Kabula, near habitation, September 1945, Purseglove 1813 (K000190112!). UNKNOWN ORIGIN. s.d., s.coll. (Heb. Requien) s.n. [P04021942!, neotype of the name Amaranthus tristis var. xanthostachys Moquin-Tandon (1849: 260) , see Iamonico (2016b)]. U.S.A. Pennsylvania, Kutztown, Rodale Research Center, 12 September 1984, Strudwick 4521 (NY00085368!); Virgin Islands, Saint John. Cruz Bay at Park Service Headquarter, wet roadside dish, sunny area, 3 January 1990, Acevedo-Rodríguez 3077 (NY882167!); Florida, Hillsborough Co.: Off I-4, just E of the I-75 exit, roadside mitigation area, dry to moist sandy soils, 21 November 2003, Moore s.n. (USF236189!).

Figures

FIGURE 1. Amaranthus rajasekharii: a. habit; b. synflorescence; c. details of synflorescence with staminate flowers; d. staminate flowers; e. pistillate flowers; f. gymnoecium; g. seed..

FIGURE 2. SEM observations: pollen grains (a. Amaranthus rajasekharii, b. A. dubius); seed coat (c. A. rajasekharii, d. A. dubius); details of seed coat (e. A. rajasekharii, f. A. dubius).