Solanum rubicaule S. Stern, 2010

Stern, Stephen & Bohs, Lynn, 2010, Two new species of Solanum (Solanaceae) from the Amotape-Huancabamba Zone of southern Ecuador and northern Peru, PhytoKeys 1, pp. 33-65 : 34-36

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Solanum rubicaule S. Stern

sp. nov.

Solanum rubicaule S. Stern sp. nov. Figs 1 View Figure 1 2 View Figure 2


Solano subinermi Jacq. et S. asperolanato Ruiz & Pav. similis sed a S. subinermi pedicellis fructiferis curvatis, a S. asperolanato habitu scandenti differt.


Peru: Cajamarca: Prov. San Ignacio, road from San Ignacio to El Chaupe, 2-3 km hike in from trailhead to El Chaupe, 5°11'56"S, 79°03'51"W, 1775 m, 17 December 2007 (fl, fr), S. Stern et al. 181 (holotype: USM!; isotypes: BM001016784!, HAO [destroyed], NY00986627!, NY00986637!, UT!).


Scandent shrub, often festooning over other plants, 1-3 m tall. Stems armed with recurved, tan to orange roselike prickles to 3 mm in length, the base 2-3 × 0.5-1 mm, moderately to densely pubescent with tan to rusty, porrect-stellate hairs, the stalks 0.5-1 mm, multiseriate, the rays 5-10, 0.1-0.2 mm, unicellular to multicellular, the midpoints nearly absent, the lateral rays often partially proximally fused (see Roe 1971 for hair terminology). Flowering portions of stem consisting of difoliate sympodial units, the leaves usually geminate, those of a pair often slightly unequal. Leaves simple, the blades 10-13 × 5-8 cm, elliptic to ovate, chartaceous to coriaceous, discolorous, adaxially reddish brown, abaxially whitish green, the adaxial surface densely pubescent with multicellular, uniseriate glandular hairs 0.3-0.6 mm long, and stellate hairs like those of the stem but with the stalks ca. 0.2-0.6 mm, the rays 3-8, ca. 0.2-0.4 mm long, the abaxial surface densely stellate-pubescent with hairs like those of the stem but with the stalks 0.1-0.3 mm, the rays 8-12, ca. 0.2-0.4 mm long; venation pinnate, the secondary veins 5-7 on both sides of the midvein, the midrib abaxially occasionally with a few recurved spines like those of the stem; base obtuse, often asymmetrical; margin entire; apex acute; leaves subsessile to shortly petiolate (to 2 cm), the petiole moderately to densely pubescent with hairs like those of the stem, occasionally sparsely armed with recurved spines like those of the stem. Inflorescences to 12 cm, extra-axillary or subopposite the leaves, unbranched to twice branched, with 2-8 flowers, the plants andromonoecious, with male flowers on young plants and hermaphroditic flowers on older plants, the axes moderately to densely pubescent with hairs like those of the stem, unarmed; peduncle 0.5-3 cm; rachis 2-8 mm; pedicels 7-11 mm in flower, 10-20 mm in fruit, distally swollen, spaced 2-4 mm apart, articulated at the base. Flowers 5-merous. Calyx 1.2-2 cm long, the tube 2-3 mm, the lobes 12-18 × 3-6 mm, triangular, densely pubescent abaxially with hairs like those of the stem; fruiting calyx slightly accrescent, incompletely covering the fruit. Corolla 3-4 cm in diameter, chartaceous, white, stellate with moderate interpetalar tissue, lobed nearly to the base, the lobes 12-16 × 4-8 mm, narrowly triangular-ovate, slightly reflexed at anthesis, densely pubescent abaxially on midvein with hairs like those of the abaxial leaf surface, adaxially glabrous. Stamens 8-12 mm; filaments 1-2 mm long, glabrous; anthers 7-10 × 1-2 mm, attenuate, connivent, yellow, linear-lanceolate, tapering, the base cordate, the apex acute, with pores directed slightly introrsely, not opening into longitudinal slits. Ovary moderately stellate-pubescent with white hairs like those of the stem; style in functionally male flowers 4-7 × 0.5-1.5 mm, not exserted beyond stamens, cylindrical, glabrous; style in hermaphroditic flowers 10-14 × 0.5-1.5 mm, exserted beyond stamens, cylindrical, glabrous; stigma to 1.5 mm wide, capitate. Fruit a berry, 1-2 cm in diameter, globose with a small acute protrusion at the apex, green, hard at maturity, glabrous, the pedicels recurved down in fruit positioning the fruits horizontal to the rachis. Seeds 25-50 per fruit, reniform, brown, rugose, ca. 3 × 2.5 mm, flattened, with a small notch where connected to placenta.


Known only from northern Peru in Dept. Cajamarca and southern Ecuador in Prov. Zamora-Chinchipe in open places in disturbed montane tropical forest, 1650-2200 m in elevation.


The flowering specimen was collected in December. Fruiting specimens were collected in December-January and March-April.


The name Solanum rubicaule is derived from the festooning growth form, reminiscent of the genus Rubus L. and the Latin " caulis " for stem.

Conservation status.

According to the IUCN Red List Categories ( IUCN 2010) Solanum rubicaule is classified as VU-B1a+B2a+B2biii; D2 (Vulnerable). The extent of occupancy is estimated to be approximately 10,000 km2 and less than five collected locations. This area of the Amotape-Huancabamba Zone has been underexplored, but collections have increased in recent years, largely due to efforts by MO in southern Ecuador and HAO in northern Peru. As this collecting continues and more specimens are determined in herbaria the number of locations should rise. Additionally, although there is continuing decline in forest habitat in this region due to deforestation for the establishment of settlements and farming, the effects of this on Solanum rubicaule are difficult to assess because it occurs in disturbed edges of forest and roadsides.

Specimens examined.

Ecuador: Zamora-Chinchipe: Cantón Chinchipe, Parroquía Zumba, trail from Guaramizal to cabin of Sandy León, W of Escuela Byron Jiménez, just S of Las Pircas, 4°46'60"S, 79°12'18"W, 2100 m, 28 March 2005 (fr), L.Bohs et al. 3336 (QCNE, UT); same locality, same date (fr) L.Bohs et al. 3338 (QCNE, LOJA, UT); same locality, 4°46'50"S, 79°12'33"W, 2000 m, 29 March 2005 (fr), L.Bohs et al. 3357 (QCNE, UT); Fundación Arco Iris, between Loja and Zamora, trail from field station to Río San Francisco, 3°59'20"S, 79°05'35"W, 2200 m, 5 April 2005 (fr), L.Bohs et al. 3425 (LOJA, QCNE, UT). Peru: Cajamarca: Prov. San Ignacio, above San Francisco (ca. a El Chaupe), 1650 m, 5 January 1995 (fr), S.Leiva et al. 1621 (HAO [destroyed], NY).


Solanum rubicaule has a festooning growth form, meaning that it is often arched and draping over other vegetation. This growth form is similar to members of Solanum sect. Micracantha Dunal, a group of vining species from the New World tropics that climb using recurved prickles. This superficial similarity explains why specimens of Solanum rubicaule are often annotated as " Solanum sect. Micracantha. " However, other morphological and molecular characters place Solanum rubicaule in Solanum sect. Torva , including flowers with triangular corolla lobes with abundant interpetalar tissue and typically branched inflorescences. Parsimony analyses of sequence data from three molecular markers (nuclear ITS and waxy or GBSSI and chloroplast trnT-F) also place Solanum rubicaule in sect. Torva ; however, the relationships within the section are not well-resolved and require further study (S. Stern and L. Bohs, unpub. data).

Following the definition of Walker and Whelan (1991), the breeding system of Solanum rubicaule is andromonoecious, meaning that there are staminate and hermaphroditic flowers on the same plant. However, a more specific description of the breeding system might be "temporally andromonoecious" since the first-formed inflorescences on a plant appear to be composed entirely of male flowers. Inflorescences on older plants are composed of hermaphroditic flowers.

Within sect. Torva , Solanum rubicaule is similar to Solanum subinerme Jacq., a species found throughout northern South America from the Guianas to central Peru, both of which have a scandent growth form and few-branched inflorescences. However, Solanum rubicaule has a distinctive infructescence with fruits held horizontal to the rachis due to pedicels that curve downward (see Fig. 2b View Figure 2 ) while Solanum subinerme has fruits held upright on erect pedicels. The adaxial leaf surface of Solanum rubicaule is unarmed, while the adaxial leaf surface of Solanum subinerme often has straight prickles to 1.5 cm long. Both species have multiseriate stalked hairs on the adaxial leaf surface but those Solanum subinerme are nearly sessile to short stalked (to ca. 0.4 mm) and very thin (ca. 0.1 mm in diameter) while those of Solanum rubicaule reach 0.6 mm with greatly thickened stalks (to 0.3 mm in diameter). Herbarium specimens of Solanum rubicaule and Solanum asperolanatum Ruiz & Pav. are very similarwith regard to pubescence and flower appearance, but the latter species has upright inflorescences that are more than twice branched, typically has>12 flowers, is a large shrub or small tree and does not have the festooning growth form of Solanum rubicaule .