Solanum sumacaspi S.Knapp

In the monograph of Solanum section Geminata (Knapp, 2002) the Peruvian collections Peyton & Peyton 147, 1026 & 1026b and Ferreyra 16683 were included in the delimitation of Solanum daphnophyllum Bitter, a similarly glabrous species from Bolivia, but with some reservations. Solanum daphnophyllum is a species of middle to high elevation (700-2800 m) dry to semi-humid forests on the eastern Andean slopes from central Bolivia to the Department of Puno in Peru (Ferreyra 16683), while S. sumacaspi is apparently only found in disturbed forests in much higher elevations (2100-3500 m) in grassland (puna)/forest transition areas in the Urubamba River drainage. Morphologically S. sumacaspi differs from S. daphnophyllum in its more elongate inflorescences with more widely spaced pedicel scars and in its pale green, exfoliating bark; S. daphnophyllum has inflorescences usually only ca. 1 cm long, and dark reddish shiny bark on all stems. The apparently geminate sympodial units also differentiate S. sumacaspi from S. daphnophyllum, which has difoliate, but not geminate, units.

Solanum sumacaspi resembles members of the Solanum nudum species group (sensu Knapp, 2002), and would key out in the first set of couplets in Knapp’s key, either with S. restingae S. Knapp and S. warmingii Hiern (both of southeastern Brazil) or with S. daphnophyllum Bitter and S. cordioides S. Knapp. Solanum sumacaspi differs from the first two in its unwinged stems and deltate calyx lobes and from the second pair by the characters detailed above with discussion of S. daphnophyllum. Solanum cordioides, an endemic species of southeastern Brazil, has a highly branched inflorescence with tiny greenish white flowers and could not be confused with S. sumacaspi.

Solanum sumacaspi also morphologically resembles two species in the Solanum arboreum species group (sensu Knapp, 2002) in its showy inflorescences of flowers all apparently opening at once; S. gratum Bitter of the Cordillera de la Costa in Venezuela and S. plowmanii S. Knapp of the western Andean slopes in Peru and Ecuador. The shiny stems also are similar to S. goniocaulon S. Knapp of the eastern Andean slopes of northern Peru and southern Ecuador, also of the S. arboreum species group. It can be differentiated from all those species by the combination of its yellowish exfoliating bark, shiny leaves that dry a very pale green, its non-anisophyllous leaves and its high elevation southern Peruvian distribution.

The following suite of characters from the synoptic key in Knapp (2002a: 42-43) will differentiate S. sumacaspi: bark of older stems exfoliating; plants completely glabrous; and possibly calyx lobes orbicular (live plants; otherwise only known in the Costa Rican species S. pastillum S. Knapp). The distribution and high elevation habitat of S. sumacaspi would further differentiate it from other superficially similar species.

Since Solanum sumacaspi appears to be relatively common in the Cusco area, fruiting collections are a priority in order to assign it to a species group with confidence. DNA sequence studies underway on a genus-wide scale in Solanum (Bohs, 2005) will certainly, however, lead to reassessment of these informal species groups based only on overall morphology.

Solanum sumacaspi occurs in the ecotone between the Peruvian puna (Young et al., 1997) and eastern slopes of the Peruvian Andes centers of plant diversity. These habitats in southern Peru are generally drier than similar grassland to forest transistion zones further to the north, and often experience a marked dry season (Young et al., 1997). Specimens of S. sumacaspi have been collected in or near the Santuario Histórico Macchu Picchu, an area with some protection from human intervention, although pressure on forests of these types from overgrazing can be severe (Kok et al., 1995; Young et al., 1997). However, most specimens appear to come from secondary or disturbed forest and forest edges, indicating either that this species is a colonizer or that the forest is highly disturbed and impacted. The conservation status of S. sumacaspi has not been formally evaluated, as no information as to population size is included on labels, but it is likely to be not at immediate threat, based on its recent collection and its apparently second growth habitat.