Pontederia gigantea Sousa, 2020

Sousa, Danilo J. L., Siqueira, Gabriela B. & Giulietti, Ana Maria, 2020, Two new species of Pontederia L. (Pontederiaceae Kunth) to South America, Phytotaxa 432 (3), pp. 252-262 : 253-256

Pontederia gigantea Sousa , sp. nov. Type —: BRAZIL. Bahia: Itajuípe, União Queimada, km 3 da rodovia para Inema,

500m da estrada, 14 May 1987, (fl.), T. S. dos Santos 4305 (Holotype CEPEC!, Isotype HUEFS!). Figures 1 A–G ; 2

A–F & 3 .

Diagnosis: — Pontederia gigantea resembles P. sagittata in its sagittate leaf blades, but differs in its blue flowers, perianth tube and lobes glabrous or with few dispersed trichomes toward the apical region, and glabrous inflorescence rachis and style, versus whitish to pinkish flowers, perianth tube, lobes and inflorescence rachis densely pilose, and puberulous style in P. sagittata .

Erect herb, 0,5 –2,5 m tall. Stem whitish to vinaceous, glabrous, internodes short. Emerged leaves alternate, distichous, petiolate; petiole 17–130 × 0.9–2.5 cm, green, glabrous; leaf blade widely elliptic to ovate, 27–35 × 19–22 cm, green, campylodromous venation, glabrous, apex acute, base sagittate; ligule fibrous to membranaceous, 3–10.5 cm long, greenish, apex truncate; submerged leaves not seen. Reproductive branch 30–165 cm long, green, glabrous. Inflorescence in thyrses of cincinni, 300–360 flowers, 4–5 flowers per cincinnus unit; peduncle 10–15 cm long., green, glabrous; spathe lanceolate, cymbiform, fused, revolute and erect at the apex, 5–7 cm long, green, glabrous, apex acute, aristate, arista 2–3 mm long; rachis 11–15 cm long, green, glabrous. Flowers blue, sessile, mid-styled, tubular, homochlamydeous; perianth tube 6–7 mm long, bluish and greenish toward the base, outer surface glabrous, sometimes with few dispersed trichomes toward the apical region, trichomes 2–2.5 mm long, without a black cell; perianth lobes 6, disposed 3+3; outer lobes 4–5 mm long, 1 lower elliptic, 2 lateral upper elliptic; inner lobes 4–4.6 mm long, 1 upper middle ovate, blue with a yellow nectar guide at the base, 2 lower lateral ovate; stamens 6, 3 longer, filaments 10–12 mm long (mid-styled), bluish, puberulous, short trichomes without a big black subapical cell; 3 shorter, filaments 6–8.5 mm long (mid-styled), bluish, puberulous; anthers sagittate to oblong, basifixed, 1–1.4 mm long, bluish; gynoecium 3-carpellate, a single functional carpel; ovary 2–3 mm long., greenish, glabrous, 3-loculate, a single ovule in the single functional locule; style 5–6.5 mm long (mid-styled), bluish, glabrous; stigma punctiform, white. Fruit utricle 7–8.6 mm long with anthocarp green, with 6 longitudinal fleshy ribs, the 3 lower bigger than the 3 upper, rib margin entire or slightly irregular. Seed 1, ovoid, 4–4.5 mm long, whitish, smooth.

Distribution and habitat:— Pontederia gigantea is endemic to Brazil, and occurs in rivers, streams and flooded riverbanks in the east coast in the Atlantic Rainforest from Bahia to Santa Catarina, forming small and dense populations with individuals reaching more than 2 m tall ( Figure 3 ).

Conservation status:— Only four or five populations are known, dispersed in the Brazilian east coast, from southern Bahia ( Northeastern Brazil) to Santa Catarina ( Southern Brazil) ( Figure 3 ), making it a relatively rare species. In Bahia, it is known from a single population in a flooded area near the Rio Almada. Because of the small population size and their association to specific aquatic situation, we based its conservation status in the area of occupancy (1.500 km 2 – assessed using GeoCAT, Bachman et al. 2011) using cell width of 0.5 km 2. Following the IUCN criteria (2016), we stated that P. gigantea is a Vulnerable species ( VU B2 ab(iii); D2) .

Phenology:— Flowering and fruiting all year round.

Etymology:— The specific epithet was chosen because of the remarkable height attained by specimens, that reach more than 2 meters tall.

Additional specimens examined (paratypes):— BRAZIL. Bahia, Itajuípe, União Queimada , 03 Dec 2017, (fl. fr.), D. J. L. Sousa 650 ( HUEFS) ; Espírito Santo, no locality, no date, (fl. fr.), A. Saint-Hilaire B2 274 ( P00635567 , P00635568 , P00635569 ) ; Rio de Janeiro, Campos , alagado próximo à lagoa de cima, 19 Sept 2008, (fl.), D. Araújo 2204 ( EAC) ; Santa Catarina, São Bento do Sul, Serra Alta, linha férrea próximo à Estrada Saraiva , 13 Feb 2016, (fl.), P. Schwirkowski 1591 ( FPS, FURB) ; São Paulo, Iguape, Peropava, fazenda Boa Vista , 17 Aug 1985, (fl.), C. B. J. Jaramillo 342 ( UEC) .

Notes:— Some specimens that occur in small rivers and streams in the Brazilian Atlantic Rainforest (from Bahia to Santa Catarina states), were identified as P. sagittata Presl (1827: 116) based mainly on the presence of sagittate leaf blades ( Castellanos 1959, Faria & Amaral 2005, Amaral et al. 2008, Sousa & Giulietti 2014, Guimarães et al. 2017, Sousa 2019). However, molecular phylogenetic studies ( Sousa 2018) provided initial evidence that specimens identified as P. sagittata comprise at least two distinct taxa. A more detailed morphological analysis P. sagittata specimens from Brazil and Mexico demonstrated morphological differences between them, supporting their delimitation as two different entities. Pontederia sagittata was described by Presl (1827) based on a specimen from Mexico (Karwinski von Karwin s.n. M 0242236!). This leads us to propose a new species based on the Brazil specimens. To ensure no other name was available, we exhaustively examined the literature and botanical collections available. A herbarium sheet collected by Sellow 278 (B 10 0242078!) in Espírito Santo-Brazil has two different determinations ( Heteranthera sagittata and Pontederia glabra ). However, neither of these names were effectively published and, supported by the International Code ( Turland et al. 2018), we choose a new specific epithet for this previously undescribed taxon.

Most species of the genus Pontederia are tristylous, presenting the three floral morphs—long-, mid- and short-styled—( Barrett & Graham 1997), except P. parviflora Alexander (1937: 59) , described as the only homostylous species of the genus. For P. gigantea , we found only one floral morph type, the mid-styled. The absence of long- and short-styled flowers can be related to a disruption of the population structure, as all of them are relatively small and distant from each other, and they could be maintained by clonal propagation. Indeed, Barrett (1988) had shown the influence of clonal propagation in tristyly breakdown of Eichhornia Kunth (1843: 129) species, also showing predomination of a mid-styled morph.

Figures

FIGURE 1. A–G. Pontederia gigantea: A. Habit. B. Inflorescence detail. C. Detail of a trichome from the inflorescence rachis and the perianth. D. Flower. E. Detail of a flower sectioned in the middle. F. Detail of a trichome from the stamen filament. G. Fruit. (A–G from D.J.L. Sousa 650).

FIGURE 2. A–F. Pontederia sagittata. A. Habit. B. Inflorescence. Pontederia gigantea. C. Habit. D. Inflorescence. E. Inflorescence detail. F. Dispersion unit. (Photos D.J.L. Sousa).

FIGURE 3. Geographic distribution of Pontederia gigantea (circles) and Pontederia reflexa (stars); BOL—Bolivia, PRY—Paraguay.