Govenia polychroma Salazar, Fernández-Díaz & Huerta-Alvízar, 2018

Salazar, Gerardo A., Fernández-Díaz, Adrián, Huerta-Alvízar, Carlos René, Jiménez-Machorro, Rolando, Cabrera, Lidia I. & Jimeno-Sevilla, H. David, 2018, Govenia polychroma, a new species of Orchidaceae from Veracruz, Mexico, Phytotaxa 343 (1), pp. 82-88 : 83-86

Govenia polychroma Salazar, Fernández-Díaz & Huerta-Alvízar , sp. nov. (Figs. 1, 2).

Type: — MEXICO. Veracruz: municipio Naranjal, El Rincón de Axalpa, cloud forest, 887 m elev., collected 30 August 2015, pressed in cultivation 5 October 2016, Fernández-Díaz & Huerta-Alvízar 37 (holotype: MEXU! isotypes: AMO! XAL!).

Diagnosis: Differing from other species of Govenia in the purplish-magenta petals with yellow apices and strongly conduplicate column foot, such that the rounded, convex inner sides of the latter are in close proximity to each other instead of leaving a wide channel between them.

Terrestrial herb 65−80 cm in height including the inflorescence. Roots several (up to 12 in our specimens), arising from the basal nodes of the corms, simple, terete, densely pubescent, to ca. 23 cm long, 2−3 mm in diameter. Corms paired, one produced the previous year and another during the current growth season, obliquely globose, somewhat compressed laterally, with 2−3 blunt basal protuberances, formed by ca. 5 internodes of which the middle one is the largest, blunt at apex, to 4.5 cm long and wide, the previous year’s one devoid of sheaths but provided with fine fibers, the new one covered by the bases of the petioles and the external sheaths; sheaths dull greyish green suffused with dark purplish-red, the lowermost 3 semi-clasping, rounded, 2.0− 4.5 cm long, the uppermost one cylindrical, subquadrate in transverse section but lacking definite angles, apex rounded, to 9.5 cm long and 2 cm in diameter. Leaves two, fully expanded at flowering time, petiolate; petioles dull green densely suffused with dark purple, sharply quadrate in transverse section, the angles distinctly keeled, 10−11 cm long, ca. 1 cm in diameter; leaf blades elliptic, subopposite, ascending-arcuate, plicate, shortly acuminate, bright grass-green on upper surface, opaque medium green with three yellowish keels on the main veins on the underside, 22−25 cm long, 9.5−12.0 cm wide near the middle. Inflorescence 40−65 cm long from the apex of uppermost basal sheath; scape purplish-red with the distal part of each internode apple-green, provided with two distant, tubular, adpressed, scarious, dark brown sheaths 4−6 cm long; raceme 16−19 cm long, producing ca. 20−40 successive flowers, several of them open at the same time, rachis apple-green with its proximal portion purplish-red. Floral bracts pale yellowish, turning at least partially scarious and dark brown at anthesis, narrowly elliptic, acute, 6−19 mm long. Flowers resupinate, relatively small for the genus (perianth aperture ca. 16 mm), loosely spaced, without a perceivable odour in the afternoon. Ovary magenta with green base, slightly arching, somewhat twisted at base, 6-costate, 20−34 mm long, ca. 2 mm in diameter. Dorsal sepal arcuate, concave, linear-lanceolate, obtuse-rounded, pale yellow with two magenta stripes on the proximal one-half externally, 13.5 mm long, 3.7 mm wide. Lateral sepals pale yellow with a magenta marginal stripe near the base, spreading, slightly concave, disposed on the same plane and somewhat convergent, falcate, obtuse-rounded, 10 mm long, 3 mm wide. Petals purplish magenta with yellow apices and darker purple veins, arcuate, recurved at apex, obliquely oblanceolate-falcate, acute, 12.5 mm long, 4.8 mm wide. Labellum pale yellow with several brownish irregular spots near the base outside, the inner surface suffused with brown below the middle, the suffusion extending distally into two narrow, curved bands each ending in a dark reddish-brown dot, with three additional dark brown dots at apex; the five dark spots are visible also on the lower surface through the labellum tissue; blade arcuate, versatile, mostly ovate, obtuse-rounded and apiculate, 9.0 mm long, 5.5 mm wide, shortly clawed at base; claw yellow, cuneate, ca. 1 mm long; proximal one-half of labellum minutely papillose, provided with two lunate prominences on the inner surface which correspond with cavities on the outer surface. Column 8.5 mm long, ca. 2.5 mm wide, arcuate, ventrally concave-channelled, white with the margins and the ventral surface with elongate brownish-red spots, provided with a round, broad auricle at each side of the stigma, base projected into a short but distinct column foot which is strongly conduplicate, such that the rounded, convex inner sides are in close proximity to each other instead of leaving a wide channel between them; externally the sides of the column foot are concave. Anther deep yellow, semi-globose, shortly rostrate, ca. 2 mm long, 1.5 mm wide. Pollinarium formed by a transversely elliptic, whitish viscidium, a short tegular, white stipe and four yellow, obliquely ovoid pollinia, these dorsiventrally juxtaposed in two pairs and joined to the stipe by short, yellowish granular caudicles. Rostellum a transverse, blunt blade. Capsule not seen.

Figure 1. Govenia polychroma . A. Flowering plant in situ at Reserva del Bicentenario, Zongolica, Veracruz (Roldan-Hernández & Jimeno-Sevilla 483). B− H, various views of a cultivated plant from El Rincón de Axalpa, Naranjal, Veracruz (Fernández-Díaz & Huerta-Alvízar 37). B. Base of plant from side showing the corms from the previous (left) and current year’s growth (right). C. Leaf blades from above. D. Inflorescence. E. Flower from front. F. Flower from side. G. Column from side (left) and front (right). H. Dissection of a flower with a ruler in centimetres for scale. Photographers: A = David Jimeno-Sevilla; B, C, F− H = Gerardo A. Salazar; D, E = Rolando Jiménez-Machorro.

Phenology:— Flowering recorded from late August to early October.

Etymology:— From Greek polychromous, many-colored, in reference to the distinctive colour of the flowers in contrasting tones of yellow, magenta, purplish-magenta, white, and brown.

Figure 2. Govenia polychroma . A. Flowering plant. B. Flower from front. C. Flower in oblique view. D. Flower from side. E. Flower with sepals and petals excised showing the labellum and column from side. F. Dorsal sepal. G. Petal. H. Lateral sepal. I. Labellum. J. Column from front prior to removal of anther cap and pollinarium. K. Column apex from front after removal of anther cap and pollinarium. L. Anther from above. M. Anther from below. N. Pollinarium from front. O. Pollinarium from back. Drawn with camera lucida by Rolando Jiménez-Machorro from Fernández-Díaz & Huerta-Alvízar 37.

Distribution and habitat:— Known only from two locations distant from one another about 16 km in a straight line in central Veracruz, Mexico. Terrestrial in leaf mould in cloud forest, from 850 to 1350 m elevation. At the type locality, the population consisted of 11 individuals growing near the base of a 20 m high rock wall, which probably confers some protection from habitat disturbance, growing alongside Ceratozamia mexicana Brogniart (1846: 8) , Piper auritum Kunth (1816: 54) , Peperomia Ruiz & Pavón (1794 : plate 8) spp., Selaginella Palisot de Beauvois (1805: 101) sp. , and trees of Inga Miller (1754 : Inga ) sp., Fraxinus Linnaeus (1753: 1057) sp. and Persea Miller (1754 : Persea ) sp., surrounded by patches of secondary-growth forest and adjacent to an abandoned coffee plantation. The other known population consisted of three plants growing on a riverside bank with riparian vegetation, in which Platanus mexicana Moricand (1833 −1846: 39−40, t. 26), Trema micrantha ( Linnaeus 1759: 937) Blume (1856: 58) , Rhamnus pompana Johnston & Johnston (1978: 38–41 , t. 5, 13) and Liquidambar styraciflua Linnaeus (1753: 999) are the most conspicuous tree species, with Piper amalago Linnaeus (1753: 29) , Xanthosoma Schott in Schott & Endlicher (1832: 19) sp., Pavonia schiedena Steudel (1841: 279) and Selaginella stellata Spring (1838: 194) in the understory.

Conservation status:— So far, only 14 individuals have been located, 11 of these at the type locality (Axalpa) growing next to a coffee plantation and under no legal protection. Three further plants were found at Reserva del Bicentenario, a bona fide 63 hectare reserve under the care of the Instituto Tecnológico Superior de Zongolica. Habitat modification or destruction in the form of clearing of natural vegetation for coffee cultivation and riverbank overflow are potential threats to the Axalpa and Zongolica populations, respectively. According to the MER-Plantas (the official method for assessing risk of extinction for plants in the Mexican law; SEMARNAT 2010), this species qualifies as Endangered because its area of distribution is ≤ 1 km 2 and the total number of individuals is ≤500. Likewise, according to the IUCN Red List Categories and Criteria ( IUCN 2012) this species should be considered as Critically Endangered since its estimated area of occupancy is <10 km 2 and severely fragmented (criteria B2(a)). We were unable to find additional specimens attributable to this species either during our numerous field trips in central Veracruz and adjacent states or in the herbaria studied. Both its showily coloured flowers and extreme rarity in nature make it a priority target for ex-situ propagation.

Taxonomic notes:— Govenia polychroma differs from other two-leaved, small-flowered species of Govenia in the elongate, sparsely-flowered raceme and the unique colouration pattern of its flowers: bright magenta ovary, yellow sepals with 1−2 external magenta stripes, dark purplish-magenta petals with yellow apices, and yellowishwhite labellum with three apical, dark purplish-brown dots and two additional dots at the end of the brown proximal suffusion on the inner surface. An additional distinctive feature is the ventral channel of the column, which is nearly completely closed by the strongly conduplicate column foot, which has approximate, convex internal margins and externally concave sides. Govenia praecox Salazar & Greenwood (1993: 113−120) , which also occurs in the cloud forests of central Veracruz, differs in flowering before the leaf blades are expanded, its dense, subcapitate raceme, yellow sepals internally suffused with red, pale yellow petals internally barred transversely with reddish-orange and wide column foot channel ( Salazar & Greenwood 1993). Another species from similar habitats in central Veracruz, G. mutica Reichenbach (1852: 856) , is distinguished at a glance by its condensed raceme and white flowers with proportionately longer, narrower floral segments (cf. Hamer 1974). Costa Rican G. viaria Dressler (2002: 26) differs from G. polychroma in its more oblique corms, short, dense raceme, pale yellow flowers with the petals barred internally, and anther bearing a subulate beak ( Dressler 2002). On the other hand, G. rubellilabia García-Cruz in García-Cruz & Sosa (2006: 259−263), from the Sierra Madre of Chiapas, is distinguished from G. polychroma by the shorter raceme with fewer (8−13) flowers and the reddish labellum rounded at apex and lacking dark spots ( García-Cruz & Sosa 2006), whereas G. matudae Greenwood & Soto Arenas (2003 : t. 590) differs in the reddish, obtuse labellum, yellow petals with reddish-orange suffusion and transverse purple bars on the distal one-third. The main differences between the new species and the aforementioned small-flowered members of Govenia are indicated in Table 1.

Govenia polychroma seems to fit in the ‘Superba group’ initially proposed by Greenwood (1981) and subsequently recovered in the morphology-based phylogenetic analysis of García-Cruz & Sosa (2005). This group includes other small-flowered species with shortly rostrate anther and predominantly yellow flowers. However, its phylogenetic position, and the overall relationships in the genus, will benefit from independent assessment using DNA sequence data. Some such work is currently in course (G. A. Salazar & L. I. Cabrera, unpubl. res.) and will eventually permit contrast of the molecular trees with the morphology-based hypotheses.

Additional specimen examined:— MEXICO. Veracruz: municipio Zongolica, arroyo La Compañía, Reserva del Bicentenario, 1314 m elev., 4 September 2014, Roldán-Hernández & Jimeno-Sevilla 483 (ZON!).