Calibrachoa irgangiana Stehmann, 2011

Stehmann, João Renato & Greppi, Julián Alejandro, 2011, Two new species of Calibrachoa (Solanaceae) from subtropical South America, Phytotaxa 25, pp. 31-38 : 32-34

Calibrachoa irgangiana Stehmann , sp. nov. ( Fig. 1.A–H , 3 A–C )

Calibrachoa caesia similis , sed viscida, caulibus decumbentibus, foliis longioribus callis evidentibus in basi nervi principalis, floribus majoribus corolla purpureae bene differt.

Type: — BRAZIL. Rio Grande do Sul: Santana do Livramento , BR293 , em direção à Quaraí, 30º 50' 40.21'' S, 55º 26' 45.63'' W, 230 m, 5 October 2006, J. R . Stehmann, L. B . Freitas & J . Fregonezi 4453 (holotype BHCB, isotypes ICN, K, MBM) .

Shrub to 0.2 m tall, viscid, decumbent with ascending and nested secondary branches, forming a cushion-like structure, trichomes 0.1–0.4 mm, simple, glandular; stems cylindrical, woody at base, grayish brown, irregularly striate yellowish-brown, sparsely viscid-pubescent on older stems, densely viscid-pubescent on younger; internodes 2–8 mm long; brachyblasts lacking or small, up to 3.2–4.0 mm long. Leaves sessile to subsessile, the blades 8–15(–17) × 5–8(–10) mm, elliptic to ovate, the apex obtuse, the base obtuse or rounded, the margin thickened, ciliate, symmetrical, slightly revolute, densely viscid-pubescent on both sides, the midrib sunken adaxially and prominent abaxially, discolorous and with a prominent ligneous callus near the base. Inflorescence of sympodial units, each composed of a single flower associated with 2 opposite leaflike bracts; pedicels 3.0– 9.5 mm long, pubescent; calyx 9.0– 12.3 mm long, olive-green to yellowish-brown, puberulent externally and internally, 10-nerved, the nerves thickened, cleft to below to the middle into lobes 4–8 mm long, unequal, lanceolate, the apex acute; corolla funnel-shaped, 14–17 mm long, externally yellow with marked purple venation, minutely pubescent, internally yellow, glabrous, the limb purple, ca. 20 mm in diam., the lobes 5–6 mm long, with purple midribs, obtuse or truncated, the apex abruptly short-acute; stamens 5, included, in 3 distinct lengths; filaments with the free portion 6–7 mm, 7–8 mm, and 10–11 mm long, the adnate portion about 3.5–4.5 mm long, glabrous; anthers yellow, 0.9–1.0 mm long, the longer pair of stamens connivent, reaching the opening of the corolla tube; nectariferous disk 2-lobed; ovary ovoid, ca. 1.5 mm long; style 9–12 mm long, the apex curved; stigma broadly dilated, situated between the pair of anthers of the middle and longer stamens. Capsule 7–8 mm long, ca. 6 mm diam., subglobose to ellipsoidal, slightly acute at the apex; fruiting pedicels 12–14 mm long, deflexed; seeds 1 mm long, ellipsoidal to globose.

Distribution:— Calibrachoa irgangiana is known from only three populations, two from the central part of Rio Grande do Sul in southern Brazil, and one in southern Misiones, Argentina. The species seems to be associated with latosoils in both regions.

Etymology:— The specific epithet is a tribute to Professor Bruno Edgar Irgang (1941–2006), a botanist responsible for the training of many taxonomists in southern Brazil.

Additional specimens examined (paratypes):— ARGENTINA. Misiones: Dep. Concepción , ruta provincial 201, km 34, 27°54’S, 55°25’W, September 2006, J . Greppi 1053 ( BHCB); ruta prov. 3, km 5.4, hacia Parque Provincial de la Sierra "Martinez Crovetto," 27º 55.6´S – 55º 31.8´W, 11 October 2009, J . Greppi 1072 ( BAB) . BRAZIL. Rio Grande do Sul: São Pedro do Sul, BR287 , em direção à São Vicente do Sul, 29º 38'18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann L. B . Freitas & J . Fregonezi 4420 ( BAB, BHCB, ICN); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4421 ( BHCB, FLOR, NY); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4422 ( BHCB); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4423 ( BHCB); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4424 ( BHCB); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4425 ( BHCB); BR287 , em direção à São Vicente do Sul, 29º 38' 18.45’’ S, 54º 18’ 16.65’’ W, 153 m, 3 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4426 ( BHCB) . Santana do Livramento , BR293 , em direção à Quaraí , 30º 50' 40.21'' S, 55º 26' 45.63'' W, 230 m, 5 October 2006, J. R . Stehmann L. B . Freitas & J . Fregonezi 4454 ( BHCB); BR293 , em direção à Quaraí , 30º 50' 40.21'' S, 55º 26' 45.63'' W, 230 m, 5 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4455 ( BHCB); BR293 , em direção à Quaraí , 30º 50' 40.21'' S, 55º 26' 45.63'' W, 230 m, 5 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4456 ( BHCB); BR293 , em direção à Quaraí , 30º 50' 40.21'' S, 55º 26' 45.63'' W, 230 m, 5 October 2006, J. R . Stehmann , L. B . Freitas & J . Fregonezi 4457 ( BHCB, RB) .

Calibrachoa irgangiana is a sticky plant, characterized by its decumbent stems, dense viscid vestiture covering the apical stems and leaves, abaxially prominent midribs with a distinctive ligneous callus at the base, purple funnel-shaped corolla, and long stamens (> 10 mm), with connivent anthers. In a front view, the anthers reach the opening of the corolla tube, a characteristic shared only by C. caesia (Sendtn.) Wijsman (1990: 101) . However, C. caesia has narrowly elliptic or linear leaves, lacks the ligneous callus, and the corolla tube usually does not exceed 10 mm in length and is internally whitish (not yellow). The leaves of C. irgangiana are similar to those of C. ovalifolia (Miers) Stehmann & Semir (1997: 419) , a species with a broader distribution in the Pampas, with which it shares the ligneous callus at the base of the midrib, but differs in its corolla color (pink to whitish) as well as in having shorter (<7 mm) stamens which are totally included inside the corolla tube. The cushion-shaped habit plus the colored blossoms make this species potentially useful for ornamental purposes.

In Misiones, the species grows in the Campo (grassland) District in the southern part of the province, but no material was found from the neighboring province of Corrientes. This region has a grassland matrix with mixed forests and represents an area of contact among the Chaco, Atlantic Forest and Pampa Provinces ( Cabrera & Willink 1980).

Following the IUCN classification, C. irgangiana should be included in the Endangered (EN) category, because few populations are known and the landscape in both regions has drastically changed in the last decades, with major destruction of its natural habitat the native grasslands (B2a,bi,ii).

Figures

FIGURE 1. Calibrachoa irgangiana. A. Habit. B–C. Stem leaves. D. Leaf vestiture. E. Leaf grandular trichomes. F. Flower in longitudinal section. G. Corolla in frontal view. H. Style. (A–H based on J.R. Stehmann et al. 4453)

FIGURE 3. Calibrachoa irgangiana: A. Habit; B--C. Flowers showing the prominent anthers (yellow) of the longest pair of stamens opening at the mouth of corolla tube. Calibrachoa longistyla: D. Habit; E. Corolla in frontal view showing the prominent style opening above the anthers of the longest stamens; F. Flower in side view showing the five stamens and the style. Photographs by J.R. Stehmann (A–E) and J.A. Greppi (F).