17. Lycium Linnaeus, Sp. Pl. 1: 191. 1753; Gen. Pl. ed. 5, 88. 1754.
Wolfberry, boxthorn [Greek lykion, name used by Dioscorides and Pliny for a spiny shrub, probably a species of Rhamnus supposedly from Lycia, ancient region of Asia Minor, alluding to resemblance]
Rachel A. Levin
Jill S. Miller
Shrubs, glabrous or hairy, leaves sometimes glaucous. Stems erect to prostrate, spinescent, with single (rarely) or multiple branches (often with divaricate branching). Leaves alternate, usually in fascicles (often drought-deciduous), petiolate or sessile, sometimes succulent; blade simple. Inflorescences axillary, fasciculate or solitary flowers. Flowers bisexual or unisexual, 4–5(–6)-merous, radially symmetric or calyx occasionally ± bilateral; calyx cupulate, tubular, or campanulate, sometimes accrescent in fruit; corolla white, greenish, yellowish, or lavender to deep purple lobes sometimes white with purple veins, tubular, funnelform, campanulate, or campanulate-rotate, lobes spreading or reflexed; stamens inserted at or proximal to midpoint of corolla tube, equal or unequal; anthers dorsifixed, ovate, dehiscing by longitudinal slits; ovary 2-carpellate; style filiform; stigma slightly 2-lobed. Fruits berries, juicy, occasionally hardened or drupaceous, globose to ovoid, rarely with constrictions (L. cooperi, L. macrodon, and L. puberulum). Seeds discoid to auriform, flattened. x = 12.
Species ca. 90 (18 in the flora): North America, Mexico, West Indies, South America, Eurasia, Africa, Atlantic Islands, Indian Ocean Islands, Pacific Islands, Australia.
Species of Lycium typically inhabit subtropical regions, often growing in desert, coastal, or saline environments. Some species can spread vegetatively via root suckering; plants have also been known to sprout from roots. Most species of Lycium are hermaphroditic; some are gynodioecious or dioecious. At least two species, L. californicum and L. carolinianum, are polymorphic for sexual strategy, having either hermaphroditic or dimorphic (gynodioecious or functionally dioecious) populations. Most species are diploid; some are polyploid. Polyploidy is positively correlated with sexual dimorphism.
Lycium appears to have evolved in South America, with subsequent dispersal to North America and a single long-distance dispersal event to the Old World. Grabowskia Schlechtendal and Phrodus Miers were formerly treated as separate genera; they have been transferred to Lycium.
SELECTED REFERENCES Chiang Cabrera, F. 1981. A Taxonomic Study of the North American Species of Lycium (Solanaceae). Ph.D. Dissertation, University of Texas. Chiang Cabrera, F. and L. R. Landrum. 2009 Vascular plants of Arizona: Solanaceae part three: Lycium. Canotia 5: 17–26. Hitchcock, C. L. 1932. A monographic study of the genus Lycium of the western hemisphere. Ann. Missouri. Bot. Gard. 19: 179–348, 350–375. Levin, R. A. and Jill S. Miller. 2005. Relationships within tribe Lycieae (Solanaceae): Paraphyly of Lycium and multiple origins of gender dimorphism. Amer. J. Bot. 92: 2044–2053. Miller, Jill S. 2002. Phylogenetic relationships and the evolution of gender dimorphism in Lycium (Solanaceae). Syst. Bot. 27: 416–428.
