Pontederia L., Sp. Pl. 1: 288. 1753.

Pellegrini, Marco O. O., Horn, Charles N. & Almeida, Rafael F., 2018, Total evidence phylogeny of Pontederiaceae (Commelinales) sheds light on the necessity of its recircumscription and synopsis of Pontederia L., PhytoKeys 108, pp. 25-83 : 25

Pontederia L., Sp. Pl. 1: 288. 1753. Figs 5 , 6 , 7 , 8 , 9

Type species (designated by Lowden 1973).

Pontederia cordata L.

Description.

Herbs perennial or annual, aquatic to amphibious, erect-emergent, procumbent-emergent or free-floating. Roots thin, fibrous or spongy. Rhizome short and generally inconspicuous. Stems trailing to erect, delicate to spongy, branching at the base, rarely branching at the upper half, rooting at the basal nodes or along the whole stem; internodes reduced to elongate, producing stolons or not. Sessile leaves distichously-alternate, congested at the apex of the stem, submerged, deciduous or persistent in mature plants, blades linear to linear-obovate, membranous, rarely chartaceous. Petiolate leaves distichously or spirally-alternate, congested at the apex of the stem or evenly distributed along the stem, floating or emergent, ligule truncate or with a flabellate projection; petioles conspicuous, rarely indistinct, inflated or not; blades elliptic to lanceolate or ovate to cordate to reniform or obovate to rounded, chartaceous to coriaceous. Synflorescence composed by a solitary main florescence subtended by a vegetative, petiolate leaf. Main florescences (inflorescences) axillary or apparently terminal, consisting of a pedunculate, many-branched thyrse, rarely a reduced thyrse; inflorescence leaf with or without an inflated leaf-sheath; basal bract flat or tubular; cincinnus’ bract absent; cincinni (1 –3–)4 - many per thyrse, alternate or fascicle-like, 1 - many-flowered, sessile or pedunculate, internodes contracted, rarely elongate; bracteoles absent, rarely present. Flowers bisexual, sessile or pedicellate, chasmogamous, pseudo-homostylous or tristylous, enantiostylous, zygomorphic, perianth connate usually forming a tube (hypanthium), rarely only basally fused, campanulate or infundibuliform or hypocrateriform, white to light pink to pink to mauve to pale lilac to lilac to bluish-lilac to purple, lobes 6 (3 outer and 3 inner), elliptic to oblong to obovate, 3 superior and 3 inferior, rarely 5 superior and 1 inferior, the central superior lobe generally with a nectar guide, consisting of 1-2 yellow to green spots, generally surrounded by a dark purple to bluish-purple, rarely white blur, spirally-coiling or revolute at post-anthesis, deliquescent or not; stamens 6, epipetalous, dimorphic (the superior 3 shorter than the inferior 3) or unequal (1 inferior longer with a differently coloured anther), filaments J-shaped or recurved-decurved, terete, glabrous to glandular-pubescent, anthers dorsifixed, sometimes basifixed, rimose or poricidal, oblong to elliptic or sagittate; ovary ellipsoid to oblongoid, glabrous, locules 3, (1-)3 fertile, (1-)multi-ovulate, placentation axial or pendulous, septal nectaries generally present, rarely absent, style J-shaped, glabrous to glandular-pubescent, stigma capitate to trilobate, rarely trifid. Fruit a capsule with loculicidal or irregular dehiscence, rarely an achene, ellipsoid to oblongoid to subglobose or ovoid, rarely pyriform, light to medium brown, apiculate due to persistent style base; anthocarp thin or hardened, smooth or ridged, ridges ornamented or not. Seeds oblongoid or ellipsoid or subglobose to broadly oblongoid or ovoid or curved narrowly ovoid, brown to light-brown, testa longitudinally conspicuously to inconspicuously winged, rarely smooth, when present, wings membranous and testa also transversally striated between each wing; funiculi generally persistent, hilum punctate; embryotega dorsal, not prominently apiculate, darker than the rest of the seed.

Distribution and habitat.

Pontederia currently comprises 26 mainly Neotropical species. Almost all Paleotropical species belong to P. subg. Monochoria (C.Presl) M.Pell. & C.N.Horn comb. et stat. nov.; except for P. natans P.Beauv., which is restricted to Africa and is a member of P. subg. Eichhornia (Kunth) M.Pell. & C.N.Horn comb. et stat. nov. Species in Pontederia can range from paludal to free-floating plants, thus occurring in a wide range of water bodies, from perennial to temporary, but most commonly in slow or stagnated water.

Generic circumscription and infrageneric classification.

The circumscription adopted by us is almost equivalent to the original one proposed by Linnaeus (1753). It differs only by the exclusion of P. ovata L., which is currently placed in Marantaceae as a synonym for Phrynium pubinerve Blume ( Horn and Haynes 1987; eMonocot 2010). Thus, no amendments are necessary for the herein adopted circumscription. We propose the subdivision of Pontederia in five monophyletic subgenera, based on the previously published molecular and morphological phylogenies ( Eckenwalder and Barrett 1986; Graham and Barrett 1995; Kohn et al. 1996; Barrett and Graham 1997; Graham et al. 1998, 2002; Ness et al. 2011), added to the new morphological and molecular analyses presented by us and data gathered by us while working on the family. Despite being monophyletic, these subgenera are not easily morphologically differentiated, since many of the characters supporting each clade are not always easy to observe, especially in dried specimens. Thus, it is our opinion that a broader sense of Pontederia should be accepted, instead of elevating each Eichhornia lineage (i.e. the herein proposed subgenera) to the generic rank.

Figures

Figure 5. Pontederia subg. Cabanisia (Klotzsch ex Schltdl.) M. Pell. & C. N. Horn. A habit B-C inflorescence: B young inflorescence, showing the inflated leaf-sheath and flat basal bract with caudate apex C mature inflorescence showing the pedunculate cincinni with elongate internodes D detail of a cincinni, showing (from left to right) an immature floral bud, a pre-anthesis floral bud and a post-anthesis flower E front view of a flower F detail of an immature capsule, showing the ridged anthocarp. All photos of P. paniculata Spreng.; A by C. Willig & L. Nusbaumer, remaining photos by M. O. O. Pellegrini.

Figure 6. Pontederia subg. Monochoria (C. Presl) M. Pell. & C. N. Horn. A-B habit: A paludal habit of P. australasica (Ridl.) M. Pell. & C. N. Horn B paludal habit of P. cyanea (F. Muell.) M. Pell. & C. N. Horn C ligule of P. vaginalis Burm. f., showing the truncate apex D-E petiolate leaf-blades: D blade of P. cyanea, showing the lack of a posterior division E blade of P. vaginalis, showing the presence of a posterior division F-G inflorescences: F inflorescence of P. australasica, showing the developed main axis G inflorescence of P. plantaginea Roxb., showing the contracted main axis H front view of a flower of P. korsakowii (Regel & Maack) M. Pell. & C. N. Horn I-J inflorescences at post-anthesis: I erect inflorescence of P. hastata L. bearing flowers at post-anthesis J infructescence of P. hastata, showing the deflexed posture and the elongated pedicels K sections of immature capsules of P. vaginalis, showing developing seeds. A, F by M. Barritt B by R. Cumming C, E, K by P. B. Pelser & J. F. Barcelona D by A. & S. Pearson G by D. Valke H by Ashitaka-f Studio and I & J by Cerlin Ng.

Figure 7. Pontederia subg. Oshunae M. Pell. & C. N. Horn. A-B habit: A dense population of the pink-flowered form B detail of a population, showing the free-floating rosettes, stolons and inflated petioles C-D petiolate leaves: C blade D detail of a young leaf showing its blade enclosing the inflated petiole of the presiding leaf E-G inflorescence: E young inflorescence of a lilac-flowered form F inflorescence of a lilac-flowered form at anthesis G inflorescence of a pink-flowered form at anthesis H-J flowers: H oblique view of a lilac flower I detail of the nectar guide J detail of the androecium and gynoecium showing the glandular hairs. All photos of P. crassipes Mart.; A by C. Willig & L. Nusbaumer B by O. Gaubert C by K. Pritchard & S. A. Harris, D-F, H-I by R. Aguilar and G by M. O. O. Pellegrini.

Figure 8. Pontederia subg. Eichhornia (Kunth) M. Pell. & C. N. Horn. A-B habit: A habit of P. heterosperma (Alexander) M. Pell. & C. N. Horn, showing the emerged petiolate leaves B habit of P. diversifolia (Vahl) M. Pell. & C. N. Horn, showing the floating petiolate leaves C-F inflorescence: C 2 - 3 - flowered inflorescences of P. diversifolia, showing the flowers with a yellow nectar guide in the posterior perianth lobes D 1 - flowered inflorescence of P. natans P. Beauv., showing the lack of a nectar guide E inflorescence of P. heterosperma, showing the lack of nectar guides in the posterior perianth lobes F morphological variation of inflorescences and perianth colour of P. azurea Sw G front view of a flower of P. azurea H front view of a flower of P. natans. A, B by O. Gaubert C by A. S. Castro D by P. Birnbaum E by H. Medeiros F by L. O. A. Teixeira G by M. O. O. Pellegrini and I by T. C. Buruwate.

Figure 9. Pontederia L. subg. Pontederia. A-C habit: A dense population of P. parviflora Alexander B population of P. ovalis Mart. ex Schult. & Schult. f. C habit of P. rotundifolia L. f. D-E petiolate leaves: D blade of P. rotundifolia E blade of P. parviflora F-H inflorescences: F inflorescence of P. cordata L., showing flowers with two yellow nectar guides in the posterior perianth lobes G inflorescence of P. parviflora, showing flowers with a sole yellow nectar guide in the posterior perianth lobes H inflorescence of P. rotudifolia, showing a lilac-flowered form I oblique view of a flower of P. ovalis J-K fruits: J detail of the apex of the infructescence of P. ovalis, showing the anthocarp with sinuate ridges K detail of an achene of P. cordata, showing the toothed ridges. A by C. Willig & L. Nusbaumer B, I, J by M. O. O. Pellegrini C by L. O. A. Teixeira, D, H by R. Aguilar E by M. R. Engels F by Ashitaka-f Studio G by M. V. Lameiras and K by A. Haines.