Cuscuta

Accepted name/Authority/Place of publication: 

CUSCUTA L., Sp. Pl. 1: 124. 1753.

Tribe: 
Cuscuteae
Synonyms: 

Anthanema Raf., Fl. Tellur. 4: 90. 1836.

Aplostylis Raf., Fl. Tellur. 4: 91.1836.

Buchingera F. Schultz, Jahrb. Pract. Pharm. Verwandte Fächer 14: 170. 1847.

Epilinella Pfeiff., Bot. Zeit. 3: 673. 1845.

Grammica Lour., Fl. Cochinch. 170. 1790.

Kadurias Raf., Fl. Tellur. 4: 91. 836.

Kadula Raf., Fl. Tellur. 4: 90. 1836.

Monogynella Des Moul., Etudes Org. Cusc. 65. 1853.

Lepimenes Raf., Fl. Tellur. 4: 91.1836.

Nemepis Raf., Fl. Tellur. 4: 91. 1836.

Succuta Des Moul., Etudes Org. Cusc. 74: 11.1853.

Pentake Raf., Fl. Tellur. 4: 90. 1836.

Type Species: 

Cuscuta europaea L.; lectotype designated by N. L. Britton & A. Brown, Ill, Fl. N.U.S. ed. 2. 3: 48. 1913.

Habit: 
Vines; stems herbaceous, filiform, greenish, yellow, orange or pink-purple, glabrous, trailing or dextrorsely twining and attached to the host(s) by numerous small haustoria.
Leaves: 
Reduced, alternate, minute scales.
Inflorescences: 
Thyrse: racemes, spikes or panicles bearing monochazial cymes (subg. Monogynella) or monochazial cymes (subgenera Cuscuta and Grammica): glomerulate, spiciform, racemiform, paniculiform, corymbiform, umbelliform or fasciculate, often compound and aggregated in large inflorescences.
Flowers: 
Bisexual, radial, sessile or pedicellate, (3–)4–5-merous, thickened-fleshy to thin-membranous, white, creamy, yellowish, pink or purple; conic-cylindrical papillae present or absent on the pedicels, perianth and ovary/capsule; laticifers are visible or not in the calyx, corolla, ovary/capsules, translucent, isolated or arranged in rows; calyx longer or shorter than the corolla tube, fused at least at the very base but distally distinct for various lengths, cylindric, cupulate or campanulate, sometimes angled or slightly zygomorphic, lobes round to lanceolate, basally overlapping or not; corolla gamopetalous, tube cupulate to cylindric; lobes imbricate in bud, initially erect, later erect, spreading or reflexed; stamens alternating with corolla lobes, inserted near the base of the sinuses, anthers open longitudinally, on short filaments, rarely sessile; infrastaminal scales commonly present, scale-like appendages dentate or fimbriate, adnate at the corolla tube base and forming a corona alternating with the corolla lobes; ovary superior, 2-locular, each locule with 2 anatropous ovules; styles 1 or 2, stigmas capitate or elongated.
Pollen: 
Heteromorphic, 3-zonocolpate in most species but this prevalent apertural type may be accompanied in the same anther by a small proportion of 4-, 5- or even 6-zonocolpate grains, and extremely rarely by pantocolpate grains. Similarly, species with preponderantly 5- and 7-zonocolpate pollen grains may also produce pantocolpate morphs. Size is only relatively homogenous within major clades of Cuscuta. Generally, the species of subg. Monogynella have the largest pollen grains, 25–37.2 µm long, while in the remaining subgenera the average is 21 µm. Supratectal ornamentation typically consists of rounded to acute scabrate processes less than 1µm, ± evenly distributed over the pollen surface. Larger supratectal conical spines, > 1µm, are characteristic of some Monogynella species. Shape prolate to suboblate, often variable within the same species and plant. Exine sculpture ranges from tectum imperforatum to reticulate. For pollen evolution see Welsh et al. (2010). Pollen images: http://www.wlu.ca/page.php?grp_id=2147&p=14649&pv=1
Fruits: 
Capsules, indehiscent or circumscissile by a ± regular line near the base, depressed, globose to ovoid. Indehiscent capsules, particularly in the species with large interstylar apertures and glomerulate inflorescences/infrutescences may occasionally rupture irregularly.
Seeds: 
1–4 per capsule, subglobose or ovoid, angled or dorsoventrally compressed; hilum terminal, subterminal or lateral; endosperm nuclear; embryo uniformly slender, 1–3-coiled, rarely globose-enlarged at the base (C. denticulata clade), without cotyledons, consisting mostly from the hypocotyl.

Chromosome details

Origin: 
Multiple locations: Asia, Europe, North America; Cuscuta is a polyploid complex with a pronounced variation of the chromosome number. Subgenus Cuscuta has holocentric chromosomes with diffuse kinetochores, which are very rare in the angiosperms. Reticulate evolution has contributed substantially to species diversity in subg. Grammica and explains in part the extensive polyploidy.
Chromosome number: 
8
10
14
16
20
26
28
30
32
38
42
44
48
56
60
Collector(s): 
Multiple collectors (see "Publications" below)
Publication(chromosome): 
Fogelberg, S.O. 1938. The cytology of Cuscuta. Bull Torrey Bot Club 65:631–645.-------- García M.A, S. Castroviejo. 2003. Estudios citotaxonómicos en las especies ibéricas del género Cuscuta (Convolvulaceae). Anales Jard. Bot. Madrid 60: 33–44. .-------- Kaul, M.L.H., A.K.Bhan 1977. Cytogenetics of polyploids VI. Cytology of tetraploid and hexaploid Cuscuta reflexa Roxb. Cytologia 42:125–136.-------- Pazy, B., U. Plitmann. 1995. Chromosome divergence in the genus Cuscuta and its systematic implications. Caryologia 48: 173–180.
Distribution: 

Cosmopolitan, except Arctic, sub-Arctic and Antarctic geographical areas. map

Ecology: 

Encountered in a wide diversity of terrestrial ecosystems: temperate to tropical forests, grasslands, deserts, mountains, and saline habitats (elevation: 0 to 3,500 m above sea level). Similarly to other parasitic plants, Cuscuta spp. are keystone species because they impact the diversity and structure of the plant communities in which they occur. Weedy species thrive in disturbed habitats: ruderal or agricultural.

Phenology

Flowering: 
In temperate climates: summer-fall; in tropical climates follow the hosts biological cycles.
Fruiting: 
Summer-fall-winter.
Common names and uses: 
The most common English vernacular name is “dodder” but various others (somewhat perjorative but vividly descriptive of the biology) have been given to this parasite: hellbine, pull-down, strangleweed, strangle-vine, tangle-gut, devil's-guts, devil's-ringlet, witches’-shoelaces, hailweed, hairweed, devil's-hair, angel’s-hair, goldthread, and love vine. Many of these names can be found in the other languages as well. Some species (e.g., C. chinensis) have been investigated for their medicinal properties and others were used in the past as dyes (e.g., C. tinctoria). For more information on ethnobotany see Costea and Tardif (2004) and http://www.wlu.ca/page.php?grp_id=2147&p=9047&pv=1
Phylogeny: 

A generic phylogeny was provided by McNeal et al (2007) but it was based on only 33 species. Three major infrageneric groups proposed by Engelmann (1859), Cuscuta, Grammica and Monogynella, provide a largely adequate backbone for the classification of the genus. Section Pachystigma, which includes several species from South Africa and is currently included in subg. Cuscuta, may require separation as a distinct subgenus. Detailed phylogenies are available for subgenera Cuscuta (García and Martin, 2007) and Grammica (Stefanović et al. 2007).

Number of Species: 
200
Infrageneric Characters: 

Inflorescence morphology; number of styles; shape of stigmas.

Subgenus Monogynella = Inflorescences thyrse; gynoecium with one style, sometimes distally bifid.

Subgenus Cuscuta = Inflorescences monochazial cymes; gynoecium with 2 equal styles; stigmas elongate: cylindrical, terete or clavate.

Subgenus Grammica = Inflorescences monochazial cymes; gynoecium with 2 unequal styles; stigmas capitate.

Commentary: 

Evolutionary relationships of Cuscuta in the morning glory family are still unresolved. The position of Cuscuta in Convolvulaceae was, however, narrowed down to these phylogenetic scenarios (Stefanović and Olmstead 2004): 1) Cuscuta as a sister to the “bifid style” clade (Dicranostyloideae) which comprises the tribes Hildebrandtieae, Cresseae, Dichondreae, and in part Convolvuleae, Poraneae and Erycibeae; 2) Cuscuta as a sister to the “bifid clade” together with “clade 1” (Convolvuloideae), which includes the tribes Ipomoeae, Argyreieae, Merremiae and some Convolvuleae; 3) Cuscuta as a sister to one of the members of the “bifid clade”—but this possibility was deemed “unlikely” and could not be formally tested because the relationships within this clade were unresolved (Stefanović and Olmstead 2004). The diversity and evolution of pollen and gynoecium structures in Cuscuta support a relationship with the “bifid clade” (Welsh et al 2010; Wright et al. 2011).

Other information: 
Cuscuta is the third most economically important group of parasitic plants (after Striga and Orobanche) as infestation by some of its species can result in significant yield losses in numerous crops. Consequently, the entire genus is often placed indiscriminately on governmental lists of “noxious weeds” or “quarantine pests”. This negative stereotype has been perpetuated by extrapolating the true danger posed by a limited number of species (~15 species worldwide) to the scale of an entire genus, regardless of the fact that the vast majority of dodders are not weeds; quite the opposite: ca. 50% of the species probably require conservation measures.
References: 

Costea, M., F.J. Tardif. 2004. Cuscuta (Convolvulaceae) — The strength of weakness: a history of its name, uses and parasitism concept during ancient and medieval times. Sida 21: 369–378.

Costea, M. and Tardif, F.J.  2006. Biology of Canadian weeds. Cuscuta campestris Yuncker, C. gronovii Willd. ex Schult., C. umbrosa Beyr. ex Hook., C. epithymum (L.) L. and C. epilinum Weihe.  Can. J. Pl. Sci. 86: 293–316.

Costea, M. 2007-onwards. Digital Atlas of Cuscuta (Convolvulaceae). https://www.wlu.ca/page.php?grp_id=2147&p=8968

Costea, M., S. Stefanović. 2009. Cuscuta jepsonii (Convolvulaceae), an invasive weed or an extinct endemic? Amer. J. Bot. 96: 1744–1750.

Costea, M., S. Stefanović. 2010. Evolutionary history and taxonomy of Cuscuta umbellata complex (Convolvulaceae): evidence of extensive hybridization from discordant nuclear and plastid phylogenies. Taxon 59: 783–1800.

Dawson, J.H., L.J. Musselman, P. Wolswinke, I. Dörr. 1994. Biology and control of Cuscuta. Rev. Weed Sci. 6: 265–317.

Engelmann, G. 1859. Systematic arrangement of the species of the genus Cuscuta with critical remarks on old species and descriptions of new ones. Trans. Acad. Sci. St. Louis 1:453–523.

García, M.A., Martin MP. 2007. Phylogeny of Cuscuta subgenus Cuscuta (Convolvulaceae) based on nrDNA ITS and chloroplast trnL intron sequences. Syst. Bot. 32: 899–916.

Hunziker, A.T. 1949. Las especies de Cuscuta (Convolvulaceae) de Argentina y Uruguay. Trab. Mus. Bot. Uni. Nac. Córdoba. Year XII: 1101–1202.

Meulebrouck, K., E. Ameloot, R. Brys, L. Tanghe, K. Verheyen, M. Hermy. 2009. Hidden in the host – Unexpected vegetative hibernation of the holoparasite Cuscuta epithymum (L.) L. and its implications for population persistence. Flora 204: 306–315.

McNeal J.R., K. Arumugunathan, J. V.Kuehl, J. L. Boore, C. W. dePamphilis. 2007. Systematics and plastid genome evolution of the cryptically photosynthetic parasitic plant genus Cuscuta (Convolvulaceae). BMC Biol 5:55

Stefanović S., R. G. Olmstead. 2004. Testing the phylogenetic position of a parasitic plant (Cuscuta, Convolvulaceae, Asteridae): Bayesian inference and the parametric bootstrap on data drawn from three genomes. Syst. Biol. 53: 384–399.

Stefanović, S., Kuzmina, M., Costea, M. 2007. Delimitation of major lineages within Cuscuta subgenus Grammica (dodders; Convolvulaceae) using plastid and nuclear DNA sequences. Am. J. Bot. 94: 568–589.

Stefanović, S., M. Costea. 2008. Reticulate evolution in the parasitic genus Cuscuta: over and over and over again. Botany 86: 791–808.

Yuncker, T.G. 1921 (1970). Revision of the North American and West Indian species of Cuscuta. Illinois Biol. Monogr. 6: 91–231. 

Yuncker, T.G. 1932. The genus Cuscuta. Mem. Torrey Bot. Club 18: 113–331. 

Welsh, M., S. Stefanović, M. Costea. 2010. Pollen evolution and its taxonomic significance in Cuscuta. Pl. Syst. Evol. 285: 83–101.

Wright, M.A.R., M. Welsh, M. Costea. 2011. Diversity and evolution of gynoecium in Cuscuta (dodders, Convolvulaceae) in relation to their reproductive biology: two styles are better than one. Pl. Syst. Evol. 296: 51–76.

Author/Editor

Author: 
Mihai Costea
Contributors: 
Classification: 

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