Gentianella viridiflora S. Pfanzelt & S.P. Sylvester, 2015

Pfanzelt, Simon, Sylvester, Steven P., Ammann, Lolita & Sylvester, Mitsy D. P. V., 2015, Gentianella viridiflora (Gentianaceae), a new species from the Peruvian Andes, Phytotaxa 222 (4), pp. 283-289 : 284-288

Gentianella viridiflora S. Pfanzelt & S.P. Sylvester , sp. nov. ( Figs. 1–3 )

Type:— PERU. Cusco: Provincia La Convención, Distrito Vilcabamba , forest towards the top of the Totora-Purkay valley on the North side of the river, 3 km East of the Totora-Purkay village , 4171 m, 13°10’50.2’’S, 73°03’33.0’’W, 7 May 2013, S. P. Sylvester 1951 (holotype USM!; isotypes K!, LPB!, MO!, OLD!, Z!) .

Differs from similar Andean Gentianella species, with several decumbent to ascendent one-flowered stems, by its yellowish-green, probably cleistogamous, flowers.

Description: —Herbaceous, tap-rooted, probably monocarpic or short-lived perennial, up to 14.5 cm tall. Stems several, branched from the lower to mid-height stem nodes, 1.0–2.0 mm thick at base, ascendent; basal internodes to 21 mm long, the distal ones slightly terete, to 38 mm long, generally twice as long as the subtending leaves. Leaves not connate at base; basal ones spatulate, 18.5–27.1 × 4.8–6.6 mm, round at apex; stem leaves spatulate to obovate-oblong, smaller distally, 6.5–12.7 × 1.5–4.3 mm, round at apex. Flowers solitary, erect, pentamerous, hermaphroditic; pedicels to 5.8 cm long. Calyx 7.3–9.0(–9.8) mm long; tube infundibuliform; lobes oblong, with shallow constrictions just below the middle, slightly spreading (when fresh), 3.3–4.8 × 1.3–2.2 mm (width at base), (0.95–)1.1–1.2 times as long as the tube, acute at apex; colleters on the adaxial side of the calyx absent. Corolla yellowish-green, lobes sometimes abaxially suffused with reddish purple at the tips and along those margins that remain uncovered in bud; corollas of terminal flowers 15.5–16.5 mm long, those of flowers of axillary branches 8.9–16.2 mm long; lobes ovate, (4.2–)7.1– 9.0 × 3.7–4.5 mm, (0.4–)0.8–1.0(–1.2) times as long as the tube, acute at apex; tube with sparse trichomes, 0.2–0.5 mm long, at the site of filament insertion and distally towards the corolla lobe sinuses, but trichomes sometimes absent. Filaments inserted at ca. 0.7–0.9 times the height of the corolla tube, the free portion 1.7–3.6 mm long. Anthers bluish, sagittate, 1.3–2.2 × 0.7–1.1 mm. Ovary cylindrical to ellipsoid, 8.5–12.9 × 1.7–2.9 mm, subsessile to stipitate upon a gynophore up to 1.1 mm long; style inconspicuous; stigmatic lobes 2, 0.6–0.8 × 0.6–0.7 mm. Nectaries 5, V- to Ushaped, one at the base of each petal. Capsule cylindrical to ellipsoid, 15.1–18.7 × 2.5–2.8 mm. Seeds dark brown, subglobose, foveate, 0.6–0.8 mm in diameter.

Distribution and habitat: — Gentianella viridiflora is only known from the type locality, the Totora-Purkay valley, where it was found to be locally abundant on heavily grazed mountain slopes on the edge of dense Polylepis pepei B.B. Simpson (1979: 32) woodland, or intermixed in more open grazed woodland, from 4100–4200 m ( Fig. 3 C–D ). Up to 40 individual plants were encountered in a single 4 m 2 -plot studied at the type locality. Indicator species analyses have retrieved G. viridiflora as a significant indicator species of disturbed puna woodland in that area (Sylvester et al., unpubl. data). It is likely that heavy grazing maintains the niche of this species as it was not observed in areas with reduced grazing, probably because of out-competition for light by tussock grasses. The plants were found associated with other low-growing forbs such as Azorella multifida ( Ruiz & Pavon 1802: 27) Persoon (1805: 303) , Belloa kunthiana (A.P. de Candolle 1836: 379) A.A. Anderberg & S.E. Freire (1991: 189) , Agrostis breviculmis A.S. Hitchcock (1905: 36) , Carex ecuadorica Kükenthal (1904: 7) , and Lachemilla pinnata ( Ruiz & Pavon 1798: 69) Rothmaler (1937: 172) . Despite thorough revision of specimens at CUZ and LPB, no other specimens of G. viridiflora have been found. However, the difficult access to valleys in the Cordillera Vilcabamba has probably led to this region being under-sampled.

Comparison with similar species: —The yellowish-green corolla of Gentianella viridiflora is very similar in colour to those of the Peruvian G. chlorantha J.S. Pringle (1986: 357) , G. thyrsoidea (Hook. 1831: 227) Fabris (1958: 88) , and G. weigendii J.S.Pringle (2012: 70) , and of the Bolivian G. macrorrhiza ( Gilg 1916: 40) Fabris ex T.N.Ho & S.W.Liu (1993: 63) . Gentianella chlorantha , from Amazonas, is a subshrub with densely spaced leaves and subsessile flowers. Gentianella thyrsoidea , from central Peru, and G. weigendii , from Ancash, both feature a single primary stem, linear leaves, and a multiflorous thyrsoid inflorescence. Gentianella macrorrhiza , from Cochabamba ( Bolivia), has a thick rhizome covered with old leaf remains, lanceolate, glossy leaves, and globose corollas.

Among Peruvian Gentianella species with yellow to yellowish-red corollas that share a similar habit with Gentianella viridiflora , G. tovariana Fabris (1955: 45) , from Huancavelica, differs in being a scapose perennial with red-tipped yellow flowers. Its corolla is glabrous within and the filaments are inserted in the lower third of the corolla tube. Gentianella chrysosphaera ( Gilg 1916: 37) Zarucchi (1993: 1255) , from Junin, is a perennial with a stout caudex, a well-developed rosette of basal leaves, a 2–4-flowered cyme, ovate calyx lobes with apiculate apices and a glabrous corolla. Gentianella chrysotaenia ( Gilg 1916: 39) Zarucchi (1993: 1255) , from central Peru, has terminal, 3-flowered cymes, and several secondary one-flowered stems that rise from the distal leaf axils. Its corolla lobes are at least twice as long as the tube. In the stout-rooted perennial G. incurva (Hook. 1831: 228) Fabris (1958: 90) , from central Peru, the corolla lobes exceed the corolla tube in length. Gentianella brunneotincta ( Gilg 1906: 37) J.S.Pringle (1993: 1255) , from north-central Peru, has subacute to acute rosulate leaves, and a glabrous corolla, which is yellow at anthesis, and whose lobes later turn brownish at the tips.

Among the white and violet to blue-flowered species from central to south-central Peru that share a similar habit with Gentianella viridiflora , G. smithii J.S. Pringle (2008: 514) , a caespitose perennial from Ancash, differs in its connate leaf bases, corolla lobes at least twice as long as the corolla tube, and glabrous corolla tube. Gentianella persquarrosa ( Reimers 1929: 332) J.S. Pringle (1986: 368) , from Cusco, is similar to G. viridiflora in habit, but differs in having a white corolla with blue streaks or blotches, and corolla lobes that are twice as long as the corolla tube. This latter species and G. potamophila ( Gilg 1916: 74) Zarucchi (1993: 1256) have obovate corolla lobes with round apices. Gentianella vargasii Fabris (1958: 86) , whose type is also from Cusco, has basally connate leaves and both calyx lobes and corolla lobes exceeding their respective tubes by ca. twice their length. Gentianella dolichopoda ( Gilg 1916: 36) J.S. Pringle (1986: 368) , from south-central Peru, has basal leaves with long, pseudopetiolate proximal portions and obovate corolla lobes that are much longer than the corolla tube. Gentianella petrophila ( Gilg 1906: 42) Zarucchi (1993: 1256) , from Junin, has subacute to acute leaves, lanceolate calyx lobes and obovate corolla lobes that are much longer than the glabrous corolla tube. Gentianella cerrateae Fabris (1955: 48) , from north-central Peru, has obovate corolla lobes with round apices, and a glabrous corolla tube. Gentianella roseolilacina ( Gilg 1906: 35) J.S.Pringle (1993: 1256) , from Ancash, differs from G. viridiflora in its acute leaves and the glabrous corolla tube. Gentianella poculifera ( Gilg 1913: 48) Zarucchi (1993: 1256) and G. calcarea ( Gilg 1906: 42) J.S.Pringle (1993: 1255) , both from Junin, have mostly acute, long-pseudopetiolate basal leaves. G. calcarea differs also in its somewhat connate cauline leaves.

Cleistogamy: —Interestingly, possibly all members of South American Gentianella with yellowish-green to green corollas so far described can be considered cleistogamous ( G. macrorrhiza, S. Pfanzelt , pers. obs., G. thyrsoidea, Gilg 1916 ; G. weigendii, Weigend et al. 5038, in sched., and Pringle 2012a). This newly discovered species does not appear to be an exception, as it was never found to have open flowers during observation over a two week period (26 April–9 May 2013) whilst at the study site, with spreading petals present only after the capsules had open.

Etymology: —The specific epithet viridiflora refers to the yellowish-green corollas of this new species.

Conservation status: —So far, G. viridiflora is only known from the type locality. As a consequence, there is no adequate information available on its distribution and population size, so it should be categorized as Data Deficient according to the IUCN Red List Categories and Criteria ( IUCN 2012). Although large populations were encountered at the type locality, the likelihood that this species has its niche maintained by consistent heavy livestock grazing raises the question over its vulnerability to changing land use, should a less intensive grazing scheme be employed.

Figures

FIGURE 1. Gentianella viridiflora. A. Habit. B. Distal portion of flowering stem. C. Calyx spread out. D. Corolla spread out, showing stamens, ovary and the nectaries. Scale bars A 2 cm, B–D 2 mm. Drawn by L. Ammann, based on the type material (S.P. Sylvester 1951).

FIGURE 2. Holotype specimen of Gentianella viridiflora (S.P. Sylvester 1951, USM).

FIGURE 3. Gentianella viridiflora, plant and habitat. A. Close up of the flowers of the holotype specimen (S.P. Sylvester 1951, USM), showing the enclosed, possibly cleistogamous flowers with yellowish-green corollas. B. Habit of the holotype specimen. C. Type locality, specimens were found on the edges of the Polylepis woodland seen in the foreground and demarcated by an arrow. D. Habitat.Photographs by S.P. Sylvester.