Ludwigia helminthorrhiza (Mart.) H.Hara

Rocha, Amanda Macêdo & Melo, José Iranildo Miranda de, 2020, Diversity and distribution of Ludwigia (Onagraceae) in Paraíba State, Northeastern Brazil, European Journal of Taxonomy 639, pp. 1-24 : 12-13

Ludwigia helminthorrhiza (Mart.) H.Hara

Figs 3 k–r, 4d–e, 5a

Material examined

BRAZIL – Paraíba • Alagoinha, Estação Experimental ; 22 Sep. 1942; fl.; Lauro Xavier s.n.; JPB [958] • Araçagi, bank of the Açude Araçagi ; 17 Mar. 2014; fr.; H.O. Machado-Filho 249; CSTR • Areia, Mata do Pau Ferro, near Açude Vaca Brava; 6 Oct. 1999; fl.; M.R. Barbosa 1864; JPB • Caldas Brandão, Cajá , temporary lake; 1 Nov. 2017; bud, fl. and fr.; A.M. Rocha & E.M. Rodrigues 27; HACAM • Gurinhém ; 23 Nov. 2015; I.C. Silva 10; IPA • Itaporanga, Fazenda Cafula ; 24 Apr. 2010; M.K. Gomes 02; CSTR • João Pessoa, bank of the river Jaguaribe, Bairro Castelo Branco ; 6 Jun. 2000; fl.; M. Costa- Santos & F.M. Barbosa 21; JPB • Monte Horebe, dam near the road to the municipality of Serra Grande; 24 Sep. 2014; fl. and fr.; J.L. Costa-Lima et al. 1873; RB • Nazarezinho, Rio Piranhas ; 12 Oct. 2007; fl.; P.C. Gadelha-Neto 1901; JPB • Olho D’água ; 22 Sep. 2015; T.A. Lycarião 34; IPA • Patos, Açude Jatobá ; 10 Jul. 1997; R.L. Leite 23; JPB • Pombal , Sítio Maniçoba II; 28 Jul. 2011; fl.; P. D’Angelis et al. 101; CSTR • Remígio ; 5 Oct. 2015; fl.; T.A. Lycarião 72; IPA • Santa Cruz, Fazenda Catolé ; 30 Jul. 1983; M.A. Sousa 1301; JPB • Santa Rita ; Jan. 1993; M.F. Agra 1917; JPB • São Bento, stream of Rio Piranhas ; s.d.; R. Medeiros et al. 06; CSTR • São José de Piranhas, Reservoir Cuncas ; 10 Jul. 2015; fl.; E. Araújo 45; RB • Sapé, Açude Salvador ; 10 Jun. 2014; fl.; H.O. Machado-Filho 548; CSTR • Sousa , Vale dos Dinossauros; 10 Oct. 2007; P.C. Gadelha-Neto 1864; JPB .

Description

Herbs exclusively aquatic, decumbent; branches angular, floating, glabrous and hirsute, with white spongy pneumatophores emerging from each branch knot. Leaves petiolate; petiole 1.2–3.0 cm long; blade 4.4–5.7 × 3.2–4.5 cm, with entire margin, membranous, orbicular, with rounded apex and decurrent base, sharply narrow at the petiole, glabrous to sparsely strigose. Flowers pentamerous, pedicellate; pedicels ca 8.5 cm long; bracteoles not visible; sepals 6–8 × 1.5–2 mm, green, lanceolate, with acute apex, external face sparsely hirsute; petals 1.3–1.6 × 1–1.1 cm, white, with basal yellow spot, obovate, unguiculated, with rounded apex; hypanthium 9–12 mm long, 5-locular; style 4.5–5 mm long, stigma capitate; stamens 10, anthers oblong; plain nectariferous disk with depressed nectaries, pilose, surrounding the base of each epipetalous stamens. Capsule 21–27 × 3–4 mm, subcylindrical, 10-ribbed, gradually tapering at the base, not internally dimorphic, pubescent. Seeds ca 1.5 mm long, obovoid, uniseriate, firmly embedded in woody coherent endocarp, raphe non-inflated, with diameter narrower than the body of the seed.

Distribution

Ludwigia helminthorrhiza is distributed in Central America, Argentina, Mexico, Paraguay, Peru and Venezuela; Africa and Madagascar ( Campos 2010). In Brazil, it is restricted to the states of Bahia, Ceará, Pará, Paraíba and Mato Grosso do Sul, associated to phytogeographic domains of the Amazon, Caatinga and Pantanal (Vieira 2015; Torres et al. 2016).

Habitat and phenology

In the Paraíba State, it was collected in dams, temporary lakes, streams and rivers, linked to three mesoregions: Sertão, Agreste and Mata, associated with the Caatinga or Atlantic Rainforest. It produced flowers all the year round and fruits between June and July and between October and November.

Conservation status (Paraíba State, Brazil) The extent of occurrence (EOO) of Ludwigia helminthorrhiza in the Paraíba State is 23 582.060 km 2,

close to the upper limit for Vulnerable status under the criterion B1. Ludwigia helminthorrhiza has an area of occupancy (AOO) of 100 km 2 which could qualify the species for the Endangered status under the criterion B2. However, L. helminthorrhiza is present at more than 5 locations and no evidence of threats or decline was observed. Ludwigia helminthorrhiza is assessed as Near Threatened (NT) in the Paraíba State.

Note

The species differs from other species of the genus in the studied area by its exclusively aquatic habit. Furthermore, it has spongy pneumatophore roots, orbicular leaves, white corolla with a yellow spot at the base and capsules with uniseriate seeds firmly embedded in woody coherent endocarp. Ludwigia helminthorrhiza belongs to Ludwigia sect. Jussiaea (= former section Oligospermum (Micheli) H.Hara ), characterized by seeds strongly embedded in a portion of the woody endocarp ( Zardini & Raven 1992).

Figures

Fig. 3. a–j. Ludwigia erecta (L.) H.Hara, A.M. Rocha 26. a. Habit. b. Flower. c. Sepal. d. Petal. e. Gynoecium. f. Detail of stigma. g. Bracteoles. h. Fruit. i. Transversal cut of the fruit. j. Seed. – k–r. L. helminthorrhiza (Mart.) H.Hara, A.M. Rocha and E.M. Rodrigues 27. k. Habit. l. Flower. m. Sepal. n. Detail of stigma. o. Fruit. p. Transversal cut of the fruit. q. Section of the endocarp. r. Seed. Illustrations by R.M.A. de Carvalho.