Oenothera hispida (Bentham) W.L.Wagner, Hoch & Zarucchi, 2015

Wagner, Warren L., Hoch, Peter C. & Zarucchi, James L., 2015, The correct name in Oenothera for Gaura drummondii (Onagraceae), PhytoKeys 50, pp. 25-29 : 26-27

Oenothera hispida (Bentham) W.L.Wagner, Hoch & Zarucchi comb. nov. Fig. 1

Basionym.

Gaura hispida Bentham, Pl. Hartw. 288. 1840.

Type.

Type. Mexico: In fields near Leon, Guanajuato, June 1837, Thomas Hartweg 1603 (Holotype: K! [Kew image]; Isotypes: BM, CAMB, G, LD!).

Schizocarya drummondii Spach, Nouv. Ann. Mus.Hist. Nat. 4: 382. 1836 [ “1835”]. Gaura drummondii (Spach) Torrey & A. Gray, Fl. N. Amer. 1: 519. 1838. Oenothera xenogaura W.L.Wagner & Hoch, Syst. Bot. Monogr. 83: 213. 2007.

Type. U.S.A. Texas: Travis Co., Austin, 1833-1834, T. Drummond III.36 (Holotype: G; isotypes: BM!, GH!, NY!, P). Note: the BM isotype is mounted on a sheet with two non-type collections of the same species: Purpus 3387 and Purpus 5383.

Gaura roemeriana Scheele, Linnaea 21: 579. 1848.

Type. U.S.A. Texas: Comal Co., New Braunfels, 1846, Ferdinand Roemer s.n. (Lectotype: MO-1833107!, here designated; Isolectotypes: CAS, HAL). The holotype at B was destroyed in World War II.

Schizocarya crispa Spach, Nouv. Ann. Mus. Paris 4: 384. 1835. Gaura crispa (Spach) D.Dietr., Syn. PI. 2: 1298. 1840.

Type. Mexico: Tamaulipas, Matamoros, April 1831, J. L. Berlandier 2313 (Holotype: G; Isotypes: BM, K, P).

Plant rhizomatous, perennial, forming extensive colonies, strigillose and often also villous. Stems 20-60(-120) cm tall, sometimes strict with a single unbranched main stem but usually somewhat decumbent with several branches from the base and usually irregular branching above. Leaves in a basal rosette and cauline, 0.5-7.5 (-9.5) × 0.1-2.2 cm; subsessile; blade narrowly lanceolate to elliptic, margin subentire to shallowly sinuate-dentate. Inflorescence a spike. Flowers 4-merous, zygomorphic, opening near sunset; floral tube 4-14 mm; sepals 7-11(-14) mm; petals white, fading red, 6-10 mm; staminal filaments 4-8.5 mm, anthers 3-6 mm; style 12-26 mm. Capsule 7-13 × 3-5 mm, erect, the body ellipsoid or ovoid, 4-angled, distal half pyramidal, the base of the pyramidal portion distinctly bulging, then immediately and sharply constricted to the terete proximal part. Seeds (2-)3-4(-8), 2-2.5 × 1-1.25 mm, ovoid, usually flattened on one or several sides by crowding in the fruit, reddish brown. 2n = 28.

Phenology and distribution.

Flowering from May through July, but sporadically as late as November. Oenothera hispida grows in sandy loam soils from the eastern half of Texas south through Mexico as far south Oaxaca. It is naturalized in Arkansas (Sevier Co.), coastal southern California, Georgia (Glynn Co.); its current status in both Arkansas and Georgia should be verified. It is considered an invasive species in California.

Oenothera hispida is the sole member of Oenothera sect. Gaura subsection Xenogaura . Raven and Gregory (1972) suggested that Oenothera hispida arose following interspecific hybridization between Oenothera suffrutescens (Ser.) W.L.Wagner & Hoch (subsect. Campogaura (P. H. Raven & D. P. Gregory) W.L.Wagner & Hoch) and a species in subsect. Stipogaura (P. H. Raven & D. P. Gregory) W.L.Wagner & Hoch, possibly near Oenothera mckelveyae (Munz) W.L.Wagner & Hoch. Hoggard et al. (2004) found that the pistillate parent of Oenothera hispida was indeed Oenothera mckelveyae or a close relative, but that the staminate parent probably came from a lineage related to Oenothera dodgeniana Krakos & W.L.Wagner or Oenothera lindheimeri (Engelm. & A.Gray) W.L.Wagner & Hoch in subsect. Gaura (L.) W.L.Wagner & Hoch. Oenothera hispida is not easily distinguished morphologically from Oenothera suffrutescens (subsect. Campogaura ), with which it shares the character of a thick stipe, and occasionally hydridizes in Texas. Oenothera hispida is an aggressively rhizomatous perennial with fruits conspicuously bulging on the distal half ( Raven and Gregory 1972). Since Oenothera hispida and Oenothera suffrutescens can be difficult to distinguish we have included a capsule of the latter in the figure (Fig. 1 -F) for comparison of key features for correct separation of the two species. The rhizomatous habit makes this species potentially invasive, despite its self-incompatibility, but so far it has established itself most aggressively only in coastal southern California ( Wagner et al. 2007). There are no other Hartweg collections of this species that anyone has seen other than the one cited above as the type collection. We have seen the holotype as an image on the Kew web site that was mistakenly filed under Gaura coccinea Pursh. The label information corresponds to the published locality given and is marked as in the Bentham herbarium.

Figures

Figure 1. Oenothera hispida (Bentham) W. L. Wagner, Hoch & Zarucchi A Habit, Mexico, Nuevo Leon, Roybal 34 (US) B Flower, lateral view, Roybal 34 (US) C Flower, face view, digital image (Ray Pistrum as " Gaura drummondii fresh flower " [http: // redsgoodvsevilcowbarn. blogspot. com / 2012 / 06 / chigger-chow-and-gaura-drummondii. html]) D Base of staminal filaments showing basal scales, Roybal 34 (US) E Capsule, Texas, Hall 213 (US) F Oenothera suffrutescens (Ser.) W. L. Wagner & Hoch capsule, New Mexico, Standley 6481 (US).