Solanum pumilum, Dunal, Prodr.

Wahlert, Gregory A., Chiarini, Franco E. & Bohs, Lynn, 2015, A Revision of Solanum Section Lathyrocarpum (the Carolinense Clade, Solanaceae), Systematic Botany 40 (3), pp. 853-887 : 882-883

10. SOLANUM PUMILUM Dunal, Prodr. 13: 287. 1852, nom. nov. for Solanum hirsutum Nutt. — TYPE: Based on Solanum hirsutum Nutt.

Solanum hirsutum Nutt., J. Acad. Nat. Sci. Philadelphia 7: 109. 1834, non Dunal (1813), nec Roxb. (1814).— TYPE: U. S. A. Georgia. Without precise locality, s.d. (fl), S. Boykin s. n. (lectotype, designated here: PH – PH 00030417!).

Solanum carolinense var. hirsutum A. Gray, Syn. Fl. N. Amer. 2: 230. 1878.—

TYPE: Based on Solanum hirsutum Nutt.

Solanum carolinense var. hirsutum D’ Arcy, Ann. Missouri Bot. Gard. 61: 840. 1974.—

TYPE: Based on Solanum hirsutum Nutt.

Upright perennial herb up to 0.2 m tall. Stems moderately to densely pubescent with sessile stellate hairs 0.4–0.8 mm in diameter, with 4–8 lateral rays, the central ray (1)2–5-celled and up to 3 mm long, unarmed or sparsely armed with tapered prickles up to 2 mm long. Sympodial units 2- to 3-foliate, sometimes plurifoliate, the leaves not geminate. Leaves simple, the blades 2.2–8.6 × 1.1–5.1 cm, elliptic to obovate, somewhat discolorous, sparsely to densely stellatepubescent abaxially, slightly less so adaxially with sessile stellate hairs 0.4–0.8 mm in diameter, with 4–5 lateral rays, the central ray 1–2-celled and up to 1.5 mm long, sparsely armed with prickles up to 3.4 mm long on the major veins abaxially and adaxially; base cuneate to attenuate; margin entire, sinuate or shallowly lobed with 2–6 lobes per side; apex obtuse to rounded; petioles 0.2–1 cm long, moderately to densely stellate-pubescent with hairs like those of the stem, unarmed or sparsely armed with prickles up to 2 mm long. Inflorescences 3–7 cm long, extra-axillary, unbranched, with 1–4 flowers, the axes moderately stellate-pubescent with hairs like those of the stem, unarmed or sparsely armed with prickles up to 2 mm long; peduncle up to 4 cm long; pedicels 1–3.5 cm in flower, weakly articulated at the base, moderately to densely stellatepubescent, unarmed or sparsely armed with prickles up to 1 mm long. Calyx 6–7 mm long, the tube 3–4 mm, the lobes 1.8–2.2 × 1.2–2 mm, deltate-triangular, the apex acuminate, densely stellate-pubescent abaxially, glabrous adaxially, unarmed or sparsely armed with prickles up to 1 mm long; fruiting calyx unknown. Corollas 1.8–3 cm in diameter, 10–16 mm long, stellate to stellate-pentagonal, chartaceous, white, the tube 1.3–1.8 mm, the lobes 4–8 × 5–7 mm, triangular, the apex acute, sparsely to moderately stellatepubescent abaxially, glabrous adaxially. Stamens with filaments 1–1.5 × ca. 0.2 mm; anthers 6–7 × 1–2 mm, narrowly lanceolate, somewhat connivent, yellow, the pores directed distally. Ovary 1.2–2 × 1.1–1.8 mm, subglobose-ovoid, glabrous; style 9–12 × 0.5–1 mm, cylindrical, straight, glabrous, exserted; stigma capitate. Fruits unknown.

Distribution and Habitat — Solanum pumilum is a narrowly distributed endemic currently found on the Ketona dolomite outcroppings near the Little Cahaba River in Bibb County, Alabama and on amphibolite outcroppings near the Coosa River in Coosa and Chilton Counties, Alabama ( Fig. 7 ). The type locality of the species is in Georgia, but it has not been found there since it was described in 1834. In 1980, Kral collected it in Bibb County, Alabama, but was unaware of the significance of his finding (R. Kral 65126 [VDB]). In 1993, Allison and Stevens made many new collections of the species in Alabama and confirmed its rediscovery ( Allison and Stevens 2001).

Phenology — Flowering between April and May.

Conservation Status — The four known specimens of Solanum pumilum from Georgia do not have useful locality data and were not used in the conservation assessment. In contrast, the 13 collections from Alabama have precise location information on the specimen labels, allowing for high-confidence post-facto assignment of coordinates. These represent five locations and populations with a restricted extent of occurrence of 22.5 km 2 and area of occupancy of 16 km 2. None of the specimens used to derive occurrence data were found in nearby protected areas, such the Cahaba River National Wildlife Refuge and the Nature Conservancy’ s Kathy Stiles Freeland Bibb County Glades Preserve, although the species has been reported from the latter ( Nature Conservancy 2014). Threats to the populations come from forestry operations and perhaps fire, although fire is needed to maintain the open glade habitat of Solanum pumilum . Given that the species is only known from vouchered specimens outside of protected areas and that its habitat is threatened by human activity, Solanum pumilum is assigned a preliminary conservation status of “critically endangered” [CR B1abc(i,ii,iii,v)].

Etymology — The specific epithet “ pumilum ” derives from the Latin word meaning dwarf or pygmy and refers to the short stature of Solanum pumilum .

Vernacular Name — Solanum pumilum is commonly known as dwarf horsenettle (also spelled with a hyphen: dwarf horse-nettle).

Chromosome Number — None recorded.

Notes — In general habit and vegetative morphology, Solanum pumilum is somewhat similar to S. carolinense , but can be differentiated by its small stature (up to 0.2 m vs. up to 1.2 m in S. carolinense ), its smaller (2.2–8.6 × 1.1–5.1 cm) obovate to elliptic leaf blades (vs. larger (2–15 × 2–10) ovate, lanceolate, or elliptic leaf blades), its inflorescence with 2–4 flowers (vs. 2–12), and its strictly white corollas (vs. blue to white). The leaf margins of S. pumilum are most often entire to sinuate, but can be shallowly lobed, and while S. carolinense also can have entire to shallowly lobed margins, they are usually moderately to deeply lobed. Ecological traits differing between S. pumilum and S. carolinense include flowers that are sweetly fragrant (vs. usually odorless in S. carolinense [ Allison and Stevens 2001]), small populations with well spaced individuals (compared to the invasive habit and dense colonies of S. carolinense ), and the restricted distribution on undisturbed dolomite and amphibolite substrates (vs. disturbed substrates and waste areas).

The name Solanum hirsutum Nutt. (1834) is an illegitimate later homonym of S. hirsutum Dunal (1813) and S. hirsutum Roxb. (1814) . Dunal (1852) corrected this by providing the replacement name Solanum pumilum Dunal. Later , both Gray (1878) and D’ Arcy (1974) recognized Solanum hirsutum Nutt. as a variety of S. carolinense and separately published new combinations. Under Art. 58 of the ICBN ( McNeill et al. 2012), when an illegitimate name is used at a different rank, its priority does not date back to the publication of the illegitimate name.

In the protologue of Solanum hirsutum, Nuttall (1834) writes “discovered by Dr. [Samuel] Boykin, in the vicinity of Milledgeville in Georgia.” Among the three known Boykin collections of this species ( PH – PH 00030417, NY–NY00821153, and E–E00190703), only the PH specimen is annotated in Nuttall’ s handwriting and is from the Academy of Natural

Sciences in Philadelphia, where he worked from 1836 until 1841, and is chosen here as the lectotype. The NY specimen was collected in Columbus, Georgia and the E specimen has no locality data, and thus we interpret these two Boykin collections to be paratypes and not duplicates of the PH sheet, which was presumably collected near Milledgeville, Georgia.

Additional Specimens Examined — U. S. A. Alabama: Bibb County, ca. 8.6 mi. NE of Centreville, ca. 0.2 mi. N of the mouth of Six Mile Creek, “ Nightshade Glade”, Ketona Dolomite outcrop ca. 0.15 mi. E of the Little Cahaba River, 26 Apr 1993 (fl), J. R. Allison & T. Stevens 7557 (NY-photocopy); ca. 8.6 mi. NE of Centreville, ca. 0.25 mi. N of the mouth of Six Mile Creek, “Double Glade North”, Ketona Dolomite outcrop ca. 0.1 mi. E of the Little Cahaba River, 26 Apr 1993 (fl), J. R. Allison & T. Stevens 7563 (NY-photocopy, US); ca. 7.9 mi. NNE of Centreville, ca. 0.25 mi. E of the mouth of Pratt Creek, perhaps 0.3 mi. to E of “Eastside Glade”, Ketona Dolomite outcrop ca. 0.2 mi. E of the Cahaba River, 2 May 1993 (fl), J. R. Allison & T. Stevens 7590 (NYphotocopy, UNA); ca. 5.6 mi. NNW of Centreville, “Hwy 5 Glade East”, Ketona Dolomite outcrop just E of AL Hwy 219, 16 May 1993 (fl), J. R. Allison & T. Stevens 7642 (NY-photocopy); ca. 5.5 mi. NNW of Centreville, ca. 0.1 mi. S of the intersection of AL Hwys. 5 and 219, “Hwy 219 Glade”, Ketona Dolomite outcrop, E side of AL Hwy 219, 16 May 1993 (fl), J. R. Allison & T. Stevens 7644 ( UNA); same locality and date (fl), J. R. Allison & T. Stevens 7645 (NY-photocopy); ca. 5.5 mi. N of Centreville, ca. 0.4 mi. ESE of the intersection of AL Hwys. 5 and 219, “ Tread-softly Glade”, ca. 100 ft. S of the road one would take from AL Hwy 219 to Schultz Creek Church, 16 May 1993 (fl), J. R. Allison & T. Stevens 7649 ( MO, NY-photocopy); same locality and date (fl), J. R. Allison & T. Stevens 7650 (NY-photocopy); ca. 8.6 mi. NE of Centreville, ca. 0.25 mi. N of the mouth of Six Mile Creek, “Double Glade North”, Ketona Dolomite outcrop ca. 0.1 mi. E of the Little Cahaba River, 5 Sep 1993 (fr), J. R. Allison & T. Stevens 7959 (NY-photocopy); ca. 9.8 mi. NE of Centreville, ca. 0.4 mi. NW of Bulldog Bend Bridge, W of “Bulldog Glade”, ca. 0.35 mi. N of the Little Cahaba River, 14 Oct 1993 (imm. fr), J. R. Allison et al. 8044 (NYphotocopy); bluffs above Cahaba River ca. 0.5 mi. S of Pratts Ferry bridge, 17 May 1980 (st), R. Kral 65126 ( VDB); Chilton County, N of AL Hwy 22, W of the Coosa River, 1 May 1994 (fl), J. R. Allison & T. Stevens 8239 ( MO, NY, VDB-n.v.); Coosa County, N of AL Hwy 22, E of the Coosa River, 1 May 1994 (fl), J. R. Allison & T. Stevens 8241 ( UNA). Georgia: Without precise locality, s.d. (fl), S. Boykin s. n. (E-scan); without precise locality, s.d. (fl), Ellis s. n. (NY-photocopy of WIS); Muscogee County, Columbus, s.d. (fl), S. Boykin s. n. (NY-scan).

Figures

FIG. 7. Distribution of Solanum dimidiatum, S. perplexum, and S. pumilum.