Major advances in our understanding of New World Morning Glories

John Wood of the Oxford team members collecting plants in Bolivia
Photo by BRM Williams

A major advance in revealing the unknown plant diversity on planet Earth is made with a new monograph, published in the open-access, peer-reviewed journal PhytoKeys. The global-wide study, conducted by researchers at the University of Oxford, lists details about each of the 425 New World species in the largest genus within the family of morning glories, thanks to an all-round approach combining standard, modern and new-generation identification techniques. 

The family of morning glories, also known as bindweeds, whose scientific name is Convolvulaceae, includes prominent members like the sweet potato and ornamental plants such as the moonflower and the blue dawn flower. In fact, one of the key conclusions, made in the present work, is that within this plant group there are many other species, besides the sweet potato, that evolved storage roots long before modern humans appeared on Earth. Furthermore, most of those are yet to be evaluated for economic purposes.

Sweet potato (Ipomoea batatas) growing as a weed in a waste ground, San Ramon, Peru
Photo by Robert Scotland

To make their findings, the research team of John Wood, Dr Pablo Muñoz Rodríguez, Bethany R.M. Williams and Prof Robert Scotland applied the “foundation monograph” concept that they had developed for similarly diverse and globally distributed, yet largely understudied groups. Usually, such groups with hundreds of species have never been surveyed across their entire geographical range, which in turn results in the existence of many overlooked new species or species wrongly named.

As a result, the monograph adds six new to science species and establishes nine new subspecies, previously recognised as either distinct species or varieties. The publication also cites all countries where any of those 425 morning glories occurs. In order to provide detailed knowledge about their identities and ecologies, the authors also produced over 200 illustrative figures: both line drawings and photos.

In their study, the scientists also investigate poorly known phenomena concerning the genus. For instance, the majority of the plants appear to originate from two very large centres, from where they must have consequently radiated: the Parana region of South America and the Caribbean Islands. Today, however, a considerable amount of those species can be found all around the globe. Interestingly, the team also notes a strong trend for individual species or clades (separate species with a common ancestor) to inhabit disjunct localities at comparable latitudes on either side of the tropics in North America and South America, but not the Equator.

Prof Robert Scotland (University of Oxford) with the evolutionary tree of Ipomoea that includes 2000 specimens sequenced for DNA
Photo by John Baker

The monograph exemplifies the immense value of natural history collections. Even though the researchers have conducted fieldwork, most of their research is based on herbarium specimens. They have even managed to apply DNA sequencing to specimens over 100 years old. The publication also provides detailed information about the characteristics, distribution and ecology of all the species. It is illustrated with over 200 figures, both line drawings and photos.

“A major challenge in monographing these groups is the size of the task given the number of species, their global distribution and extensive synonymy, the large and increasing number of specimens, the numerous and dispersed herbaria where specimens are housed and an extensive, scattered and often obscure literature,”

comment the scientists.

“Unlike traditional taxonomic approaches, the ‘foundation monograph’ relies on a combination of standard techniques with the use of online digital images and molecular sequence data. Thereby, the scientists are able to focus on species-level taxonomic problems across the entire distribution range of individual species,”

they explained.

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In a separate paper, published in Nature Plants last November, the research team provides further insights into how they have assembled the monograph and include all the molecular sequence data and phylogenetics produced during their work.

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Original source:
Wood JR.I, Muñoz-Rodríguez P, Williams BR.M, Scotland RW (2020) A foundation monograph of Ipomoea (Convolvulaceae) in the New World. PhytoKeys 143: 1-823. https://doi.org/10.3897/phytokeys.143.32821


Scientists challenge notion of binary sexuality with naming of new plant species

A collaborative team of scientists from the US and Australia has named a new plant species from the remote Outback. Bucknell University biology postdoctoral fellow Angela McDonnell and professor Chris Martine led the description of the plant that had confounded field biologists for decades because of the unusual fluidity of its flower form. The discovery, published in the open access journal PhytoKeys, offers a powerful example of the diversity of sexual forms found among plants.

The new species of bush tomato discovered in remote Australia provides a compelling example of the fact that sexuality among Earth’s living creatures is far more diverse – and interesting – than many people likely realize.

Bucknell University postdoctoral fellow Angela McDonnell and biology professor Chris Martine led the study following an expedition last year to relocate populations of the new plant, which were first noted by Australian botanists during the 1970s.

Herbarium specimens from those few earlier collections are peppered with notes regarding the challenge of identifying the sexual condition of this plant, which appeared at various times to be female, male, or bisexual.

 S. plastisexum flower

According to Martine, about 85% of the planet’s quarter-million flowering plant species have flowers that are bisexual – with both male and female organs present in every blossom.

“So that’s already quite different than what some people might expect; but the remaining 15% or so come in all sorts of forms that push the envelope further, including unisexual flowers and (like we see in a plant like Cannabis) whole plants that are either male or female.”

“For the most part, a given plant species will stick to one primary and predictable type of sexual expression,” said Martine “but what makes Solanum plastisexum stand out is that it is one of a just a few plants that kind of do it all. It really seems like you never know what you’ll get when you come across it.”

When DNA studies in Martine’s lab offered proof that these plants were not only all the same thing, but a species not yet described, he, McDonnell, Jason Cantley (San Francisco State University), and Peter Jobson (Northern Territory Herbarium in Alice Springs) set out to hunt for populations along the unpaved Buchanan Highway in the remote northwestern region of the Northern Territory.

The botanists were able to collect numerous new specimens and have now published the new species description in the open-access journal PhytoKeys, choosing the name Solanum plastisexum as a nod to the notable variation exhibited by this plant in its sexual condition.

“This name, for us, is not just a reflection of the diversity of sexual forms seen in this species,” wrote the authors in the article. “It is also a recognition that this plant is a model for the sort of sexual fluidity that is present across the Plant Kingdom – where just about any sort of reproductive form one can imagine (within the constraints of plant development) is present.”

Also known as the Dungowan bush tomato, Solanum plastisexum is a distant cousin of the cultivated eggplant and is a close relative of two other Australian species recently discovered by Martine and colleagues that were also published in PhytoKeysSolanum watneyi, named for Mark Watney, the space botanist of the book/film The Martian; and Solanum jobsonii, a species named last year for S. plastisexum co-author Jobson.

S. plastisexum with scientist Jason Cantley

The scientists hope that the naming of this latest new species turns a spotlight on the fact that nature is full of examples for the myriad ways in which living things behave sexually.

“In a way, S. plastisexum is not just a model for the diversity of sexual/reproductive form seen among plants – it is also evidence that attempts to recognize a “normative” sexual condition among the planet’s living creatures is problematic.”

“When considering the scope of life on Earth,” the authors conclude, “The notion of a constant sexual binary consisting of two distinct and disconnected forms is, fundamentally, a fallacy.”

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Bucknell sophomore Heather Wetreich, who measured and analyzed the physical characters of the new species using plants grown from seed in a campus greenhouse, joins McDonnell, Cantley, Jobson, and Martine as a co-author on the publication.

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Original source:

Citation: McDonnell AJ, Wetreich HB, Cantley JT, Jobson P, Martine CT (2019) Solanum plastisexum, an enigmatic new bush tomato from the Australian Monsoon Tropics exhibiting breeding system fluidity. PhytoKeys 124: 39-55. https://doi.org/10.3897/phytokeys.124.33526