THE GENUS IPOMOEA

Nuclear phylogeny of <i>Ipomoea</i>. Branches without numbers have 100% support.
Nuclear phylogeny of Ipomoea

Carl Linnaeus described the plant genus Ipomoea L. and seventeen species in the first edition of his Species Plantarum, in 1753. Since then, more than 3,000 names associated with the genus have been published, making Ipomoea the largest genus in the family Convolvulaceae. Ipomoea includes herbs, shrubs, lianas and trees and is present in all tropical and subtropical regions of the world, from sea level to 4,000 meters and from tropical rain forests to semi-desert coastal environments. The genus is also present in other more temperate regions as far North as Canada and several widespread species have a worldwide distribution. Around two thirds of the currently 805 recognised species are distributed in the Americas and the other third in the Old World.

Two species have global importance as crops: the sweet potato or sweetpotato, Ipomoea batatas (L.) Lam., and the kang-kong or water spinach, I. aquatica Forssk. Several species are cultivated in gardens —the group is commonly known as morning glories— and some species have become invasive, for example I. cairica (L.) Sweet, I. indica (Burm.) Merr. and I. purpurea (L.) Roth. In addition, multiple studies have identified anti-tumorous properties of different compounds obtained from Ipomoea leaves and roots.

Several genera treated as independent in previous works have now been confirmed to be nested within Ipomoea. These genera are: Argyreia, Astripomoea, Blinkworthia, Lepistemon, Lepistemonopsis, Rivea, Stictocardia and Turbina. All species belonging to these genera were given names in Ipomoea in our most recent paper.

Some genera in the family Convolvulaceae (either currently or formerly recognised) have been subject to comprehensive nomenclatural and/or taxonomic studies in recent times —e.g. Argyreia Lour., Convolvulus L. or Seddera Hochst.—, but most genera are poorly known taxonomically, and few studies include molecular data. In the case of Ipomoea, hundreds of studies have been published in the last two centuries but few of them addressed the taxonomy of the whole genus. Most taxonomic studies focussed on small groups of species, frequently related to the sweet potato or widespread species, or a single taxon. A few authors also addressed the genus at the national or regional level; although several of those more extensive treatments date back to the 19th century or the first half of the 20th century and most of these, with a few notable exceptions, are mere checklists of species or provide only incomplete information about the taxa included. The only global taxonomic review of the genus was published by Choisy more than 170 years ago, in De Candolle’s Prodromus, and included 282 species. Choisy’s work is now certainly outdated, considering we estimate the genus includes between 800 and 1000 extant species.

In summary, at the beginning of our project in 2012 information about the genus Ipomoea was abundant but fragmentary, with a few species very well known for many aspects of their biology but most other species never having been studied properly. The level of taxonomic knowledge of the group was generally poor and recent estimates indicate that at least 50% of all herbarium collections of Ipomoea could be misidentified. In this context, a global, comprehensive taxonomic and phylogenetic review of the genus was urgently needed —and that is the aim of our project: to study the genus, at different scales, across its entire distribution.

Text last updated 20th April 2020.

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