23. Cucurbita Linnaeus, Sp. Pl. 2: 1010. 1753; Gen. Pl. ed. 5, 441. 1754. name conserved.
Squash, gourd [Latin name for gourd] Squash, gourd [Latin name for gourd]
Plants sometimes shrublike in cultivated forms of C. melopepo, annual or perennial, monoecious, procumbent and trailing or climbing; stems <annual, often sulcate or angled>, hairy; roots tuberous or fibrous or a taproot; tendrils 2–7-branched or absent. Leaves: blade suborbiculate to broadly ovate, ovate-lanceolate, reniform, or triangular, usually deeply to shallowly palmately (3–)5(–7)-lobed, sometimes unlobed or 2-lobed, lobes depressed-ovate, ovate, broadly or narrowly triangular, or obovate to lanceolate, oblanceolate, oblong-lanceolate, or subrhombic, <base truncate to cordate>, margins serrate to denticulate or mucronulate, surfaces eglandular or glandular, glands scattered, sessile or stipitate to peltate. Inflorescences: staminate flowers solitary [in axillary fascicles]; pistillate flowers solitary, from different axils than staminate; floral bracts absent. Flowers: hypanthium campanulate, cylindric, or cupulate; sepals 5, <straight, erect>, subulate-linear to lanceolate [spatulate]; petals 5, <often recurving>, connate 1/2 length, cream or yellow to orange, broadly ovate to oblong-ovate, oblong-elliptic, triangular, triangular-ovate, or lanceolate-ovate, 25–90[–120] mm, pubescent to puberulent, corolla campanulate. Staminate flowers: stamens 3; filaments inserted at hypanthium base, distinct or slightly connate; thecae connate, forming central oblong body, sigmoid-flexuous, connective narrow; margins differentiated or not in thickness, texture, and color, surface smooth or slightly rough to punctate-sculptured. x = 20.
Species 14–22 (9 in the flora): North America, Mexico, West Indies, Central America, South America; introduced nearly worldwide.
Species of Cucurbita have long provided fruits that are staples of the world’s diet. Radiocarbon dates for C. pepo from Guilá Naquitz Cave in subtropical central Oaxaca, Mexico, document the earliest known cultivation of a squash––between 10,000 to 8000 calendar years ago (B. D. Smith 1997)––predating the appearance of maize, beans, and other directly dated domesticates in the Americas by about 4000 years. The oldest known cultivated maize cobs also have come from Guilá Naquitz Cave, dated about 6250 calendar years ago. Cultivated cucurbits were introduced into the Old World quickly after the discovery of the New World (H. S. Paris et al. 2006), and since the 17th century they have spread over the tropics and subtropics and temperate regions. After its introduction to the Old World, C. pepo apparently underwent secondary diversification in Europe and/or Asia Minor (J. R. Harlan 1951).
Cucurbita has been divided into two groups (T. W. Whitaker and W. P. Bemis 1975): the arid-zone perennials with tuberous storage roots, and the more mesophytic annuals or short-lived perennials without storage roots. Four of the domesticated species (C. argyrosperma K. Koch, C. maxima, C. moschata, and C. pepo) plus one wild species (C. ecuadoriensis Cutler & Whitaker) comprise the mesophytic lineage (O. I. Sanjur et al. 2002). One other among the mesophytic domesticated species, C. ficifolia, is outside the mesophytic clade and basal to it.
Uncertainty about the number of species in the genus reflects two areas of subjectivity: some domesticated species are commonly treated as conspecific with a wild species when a derivative-progenitor relationship is indicated––the domesticated Cucurbita maxima arose from the wild C. andreana Naudin of South America; and, the taxonomic status of some entities is not unambiguously resolved––C. digitata was treated by M. Nee (1990) to include four taxa, three of which are sometimes treated as distinct species. In any case, the geography and morphology of all the entities potentially treated at specific rank is fairly well understood. Additionally, Nee has noted that a wild ancestor of C. moschata, from reports from Colombia, may remain to be discovered and described; similarly, he has predicted that the wild ancestor of C. ficifolia exists somewhere in the Andes.
Four of the domesticated species are treated here because they sometimes are encountered in the flora area outside of cultivation; in most cases, these plants can be characterized as waifs, as they apparently do not maintain themselves in persistent populations for more than one or a few years.
Cucurbita argyrosperma K. Koch (Japanese pie pumpkin, white cushaw) is currently grown in the United States and known to have been in cultivation in eastern North America since pre-Columbian times (G. J. Fritz 1994); it has not been reported to grow outside of cultivation in the flora area.
Identification of species among plants of domesticated Cucurbita often is difficult (especially among C. maxima, C. melopepo, C. moschata, and C. pepo) because habit, vestiture, leaf shape, and floral characters commonly show parallel variation, and fruit shape and size are highly variable.
SELECTED REFERENCES Bailey, L. H. 1943. Species of Cucurbita. Gentes Herb. 6: 266–322. Bemis, W. P. and T. W. Whitaker. 1969. The xerophytic Cucurbita of northwestern Mexico and southwestern United States. Madroño 20: 33–41. Decker, D. S., T. W. Walters, and U. Posluszny. 1990. Genealogy and gene flow among annual domesticated species of Cucurbita. Canad. J. Bot. 68: 782–789. Nee, M. 1990. The domestication of Cucurbita (Cucurbitaceae). Econ. Bot. 44(3,suppl.): 56–68. Rhodes, A. M. et al. 1968. Numerical taxonomic study of Cucurbita. Brittonia 20: 251–266. Sanjur, O. I. et al. 2002. Phylogenetic relationships among domesticated and wild species of Cucurbita (Cucurbitaceae) inferred from a mitochondrial gene: Implications for crop plant evolution and areas of origin. Proc. Natl. Acad. Sci. U.S.A. 99: 535–540. Whitaker, T. W. and W. P. Bemis. 1975. Origin and evolution of the cultivated Cucurbita. Bull. Torrey Bot. Club 102: 362–368. Wilson, H. D. 1990. Gene flow in squash species. BioScience 40: 449–455. Wilson, H. D., J. Doebley, and M. Duvall. 1992. Chloroplast DNA diversity among wild and cultivated members of Cucurbita (Cucurbitaceae). Theor. Appl. Genet. 84: 859–865.