Distribution. Morning glories occur in the tropics of the world although some species also reach temperate zones. The greatest species diversity occurs in the Americas and Africa. Some genera extend around the world; others are endemic to one land mass. Ten are endemic to the Americas (Aniseia, Dicranostyles, Evolvulus, Iseia, Itzaea, Lysiostyles, Maripa, Odonellia, Stylisma, Tetralocularia); Africa has 13, and Asia has 10. Bonamia, Ipomoea, Merremia, and Operculina are genera that are distributed throughout the tropics.
Family Classification. Hallier (1893) divided the family into the groups Echinoconeae (spiny pollen) and Psiloconeae (comparatively smooth pollen). Recent phylogenetic evidence supports the conclusion that the Echinoconeae are monophyletic (Austin 1998). These groups are subdivided into several tribes. Since the 1890s most people have recognized tribes Argyreieae, Convolvuleae, Cresseae, Dichondreae, Erycibeae, Hildebrandtieae, Ipomoeeae, and Poraneae. The placement of genera in tribes, however, has changed considerably in the past 30 years as morphology of the species has become better known (cf. Austin 1973, Sebsebe & Austin 1996).
Several authors have suggested that the family most closely related to Convolvulaceae is the Solanaceae, while others nominate the Polemoniaceae or Boraginaceae. A new study suggests that the Hydrophyllaceae may be closer to the Convolvulaceae than either of these (Austin 1998). However, since few species have been examined with new genetic techniques (cf. McDonald & Mabry 1992), the relationships remain controversial.
Number of genera and species. There are 55 genera and 1600-1700 species of Convolvulaceae. Twenty-one (21) genera and at least 750 species (44% of the family) are native in the New World. The largest New World genera are Ipomoea (ca 600 world species), Jacquemontia (ca 115 species), and Evolvulus (ca 98 species). Twelve genera have a single species; those in the Americas are Iseia, Itzaea, Lysiostyles, and Tetralocularia.
Features of the family. Stems are either herbaceous or woody. Many species have twining, climbing or trailing stems, but others are erect and may reach 2 m (Ipomoea carnea ssp. fistulosa) or even 5-15 m (Ipomoea arborescens). Stems of prostrate species may be only 10 cm long (e.g., Dichondra). A few species root from the stems, notably Ipomoea batatas and Evolvulus nummularius. Vegetative parts have milky latex that may be inconspicuous or obvious.
Leaves are alternate and commonly cordate in outline, but vary to hastate, oblong, or linear. A few cases are known where the leaves are reduced to scales (e.g., Merremia aturensis). Margins are unlobed or divided into palmate or pinnate divisions. Petioles vary from absent to longer than the leaf blades and are channeled on the upper surface. Pubescence is largely 2-branched, but may be glandular or stellate (Jacquemontia, Ipomoea & Merremia).
All members of the family have bisexual flowers except for the unisexual African Cladostigma and Hildebrandtia (Sebsebe & Austin 1996). Inflorescences may be terminal, axillary or in both positions. Inflorescences vary from being solitary flowers to complex clusters derived from dichasia. From the basic 3-flowered dichasium, monochasia have arisen in several lineages.
The smallest flowers are less than 1 cm across (Dichondra). The American Ipomoea alba (9-15 cm long) vies with the Australian I. saintronanensis (8-12 cm long) for the largest flowers in the family; both are moth pollinated. Flowers have five free, overlapping sepals, five fused petals, five separate stamens alternating with the petals, and one pistil. Corolla shape varies from rotate to bell-shaped to funnel-shaped to salver-shaped. Anthers dehisce longitudinally, but twist into a spiral in Merremia, Operculina and their relatives. The pistil is of two carpels (3-5 in Ipomoea series Pharbitis) to produce a superior, compound ovary with the same number of locules as carpels. Styles are terminal, single, or divided apically or the full length, to produce two distinct stylar branches (e.g., Bonamia, Evolvulus). There are paired bracts or bracteoles below the flowers and some of these are enlarged to form an involucre (e.g., Odonellia, some Jacquemontia).
Fruits are often capsular, but utricular fruits or berries also occur. Size ranges from 2-3 mm long (Dichondra, Evolvulus) to 30-40 mm long (Maripa panamensis, Merremia discoidesperma). Most fruits have a single layer (pericarp) surrounding the seeds, but a few have perisperm (e.g., Itzaea, Maripa) probably derived from an inner layer. Dehiscence is generally longitudinal into four segments that may divide further (Itzaea, Jacquemontia). Other fruits are indehiscent (tribes Erycibeae, Poraneae) or split irregularly (Merremia discoidesperma, M. tuberosa). Seeds vary from 1-4, through abortion, and have large, curved or folded embryos. The endosperm is homogeneous and cartilaginous. Germinating seeds produce two cotyledons that are often bifid. Cotyledons emerge directly from the broken seed coat and are produced above-ground (epigeous) except in Merremia discoidesperma and M. tuberosa that are hypogeous.
Natural history. Convolvulaceae range from tropical rainforest to savannas, prairies, and deserts. Life-forms have been modified into low-creeping herbs or even trees (Ipomoea in the Americas; Humbertia in Madagascar). Species often grow at low elevations, but a few reach ca 3000 m.
Pollination is frequently by bees (cf. Austin 1997). We have records of visits by 19 genera in four families (Andrenidae, Anthophoridae, Apidae, Halictidae). Bees of the Anthophoridae are particularly frequent visitors. There is such a close relationship with anthophorid bees that the genera Ancyloscelis, Cemolobus, and Melitoma use pollen only from Ipomoea to provision their nests. Some Diadasia use only pollen from Calystegia and Convolvulus. Moths, birds, and bats also pollinate flowers. Pollination was recently documented for both Mexican and African bats (Phyllostomatidae subfam. Glossophaginae, Anoura sp., Choeronycteris mexicana, Glossophaga soricina, and Leptonycteris sanborni; Pteropdidae, genus uncertain, eitherEidolon or Megaloglossus).
One genus of beetles (Megacerus, family Bruchidae) is a specialist whose larvae feed on the seeds of the family. Often there is a single species of beetle on one plant species, e.g. Megacerus capreolus on Merremia tuberosa.
Mode of dispersal is comparatively poorly known, but animals, wind, and water are vectors. Fleshy fruits are dispersed by birds and other vertebrates. Maripa is known as "monkey syrup" in the Guianas, and is spread by them. Fruits of the tribe Poraneae (e.g., Calycobolus) are dispersed by wind. Iseia, Tetralocularia and Old World Stictocardia fruits have internal flotation structures that facilitate spread by water. Water, and perhaps wind, spread the woolly seeds of many species. In addition, many seeds have cavities within the embryo and endosperm. A number of these "labyrinth seeds" are associated with water dispersal (e.g., Ipomoea alba, Merremia discoidesperma).
Economic uses. Perhaps the oldest use for the family is as a purgative. Many species were famous and became called "jalap," after the original source Ipomoea jalapa. This intestinal use persists in many places. Numerous American species are called "quiebra platos" or "tumba vaqueros," in reference to their laxative nature. Chemicals involved with alimentary stimulation, and other actions, are resins, calystegines, tropinone, hygrine alkaloids, pyrrolizidine alkaloids, coumarins (umbelliferon and scopoletin), and hydroxycinnamic acid alkyl esters (hexadecyl p-coumarate and octadecyl p-coumarate) (Jenett-Siems et al. 1993; E. Eich, in litt. 1996).
Several species are used as ornamentals, usually for their flowers. Europeans introduced some into Asia by the 1500s. By the early 1600s American Ipomoea in Japan -- later dubbed "Japanese Morning Glory -- had become the "most honorable flower." In 1979 the South American "blue daze" (Evolvulus glomeratus), named for its "dazingly" blue flowers, was introduced into cultivation in Florida. By 1989, it had reached Australia, Asia, Europe, and Hawaii.
The best known ornamentals are the native American species Ipomoea tricolor, I. purpurea, and I. nil. The first of these has been marketed for decades under the cultivar names "Heavenly Blue," and "Pearly Gates." These names were applied before it was known that the seeds contained small amounts of hallucinogenic ergoline alkaloids. This physiological effect was discovered by the native Americans of Mexico before Europeans arrived, and only rediscovered by R. E. Schultes of Harvard in the 1940s. His discovery led to a cult resurgence of recreational seed use by North Americans in the 1960s and 1970s. Most often used were Ipomoea tricolor ("piule," Mazatec; "badoh negro," Zapotec) and the similarly psychomimetic Turbina corymbosa ("ololiuqui," Nahuatl).
The "sweet potato," "camote," "batata," or "yam," (Ipomoea batatas) is the world's 7th largest food crop. Although of New World origin, this species is now eaten through the world, with China growing ca 80% of the crop. In the Americas, sweet potato is often displaced as a staple food by manioc (Manihot esculenta, Euphorbiaceae). Instead of being a staple, sweet potato is relegated to a holiday plant ("Dia de los Muertos" in Mexico, cf. Contreras et al. 1995; "Thanksgiving Day" in the USA), an emergency food, or used as red coloring in Amazonian South America for "masato" (a mild alcoholic beverage inoculated for fermenting by women chewing cooked manioc roots).
In North America, people usually know only the weedy species of the Convolvulaceae. Particularly infamous are the bindweeds (Calystegia spp. and the introduced Convolvulus arvensis). Both genera cause heavy annual losses to agriculture and home gardeners. Two species are on the Federal Noxious Weed List, "little bell" (Ipomoea triloba) and "water spinach" (Ipomoea aquatica).
References:
Austin, D. F. 1973. The American Erycibeae (Convolvulaceae). Maripa, Dicranostyles & Lysiostyles--I. Systematics. Ann. Missouri Bot. Gard. 60: 306-412.
Austin, D. F. 1988. Taxonomy, evolution and genetic diversity of sweet potatoes and related wild species. Pp. 27-60, In: Exploration, Maintenance and Utilization of Sweet Potato Genetic Resources. Proceedings of the Planning Conference, Centro Internacional de la Papa, Lima, Peru.
Austin, D. F. 1997. Dissolution of Ipomoea ser. Anisomerae (Convolvulaceae). J. Torrey Bot. Soc. 124:(2):140-159 (in press).
Austin, D. F. 1998. Parallel and Convergent Evolution in the Convolvulaceae. In. Mathews, P. (ed.). Biodiversity and Taxonomy of Flowering Plants, Calicut University, Calicut, India (in press).
Austin, D. F. and P. B. Cavalcante. 1982. Convolvulaceas de Amazonia. Publ. Avulsas No. 36, 134 pp., Museu Emilio Goeldi, Belem..
Austin, D. F. and R. A. Pedraza. 1983. Los generos de Convolvulaceae en Mexico. Bol. Soc. Mex. Bot. 44: 3-16.
Austin, D. F. and Z. Huaman. 1996. A synopsis of Ipomoea (Convolvulaceae) in the Americas. Taxon 45: 3-38
Contreras, J., D. F. Austin, F. de la Puente and J. Diaz. 1995. Biodiversity of sweetpotato (Ipomoea batatas, Convolvulaceae) in southern Mexico. Economic Botany 49: 286-296.
Hallier, H. 1893. Versuch einer naturlichen Gliederung der Convolulaceen auf morphologischer und anatomischer Grundlage. Bot. Jahrb. Syst. 16: 453-591.
Jenett-Siems, K., M. Kaloga, and E. Eich. 1993. Ipangulines, the first pyrrolizidine alkaloids from the Convolvulaceae. Phytochemistry 34(2): 437-440.
McDonald, J. A. 1991. Origin and diversity of Mexican Convolvulaceae. Anal. Inst. Biol. Univ. Auton. Mexico, Ser. Bot. 62: 65-82.
McDonald, J. A. and T. J. Mabry. 1992. Phylogenetic systematics of New World Ipomoea (Convolvulaceae) based on chloroplast DNA restriction site variation. Pl. Syst. Evol. 180: 243-259.
Sebsebe D. and D. F. Austin. 1996. Generic delimitation and relationships in the tribe Hildebrandtieae (Convolvulaceae). Pages 409-420, In: Maesen, L. J. G. van der, X. M. van der Burgt, and J. M. van Medenbach de Rooy (eds.). 1996. The Biodiversity of African Plants: Proceedings, XIVth AETFAT Congress, 22-27 August 1994, Wageningen, The Netherlands. Kluwer Academic Publishers, Dordrecht.
Smith, Nathan P., Scott A. Mori, Andrew Henderson, Dennis Wm. Stevenson, and Scott V. Heald (eds). Families of Neotropical Plants. New York Botanical Garden, Bronx, NY, and Princeton University Press, Princeton. NJ. .
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