Celebrating excellence in plant systematics research: Phytokeys’ 200th issue

For almost 12 years now, PhytoKeys has been providing high-quality, peer-reviewed resources on plant taxonomy, phylogeny, biogeography and evolution, freely available open access.

PhytoKeys, Pensoft’s open-access, peer-reviewed botany systematics journal, has been around for over a decade. Since its launch in 2010, it has published almost 30,000 pages in more than 1,200 works. As PhytoKeys hits the milestone of its 200th issue – which presented a monograph of wild and cultivated chili peppers – there’s plenty to look back to.

For almost 12 years now, PhytoKeys has been providing high-quality, peer-reviewed resources on plant taxonomy, phylogeny, biogeography and evolution, freely available open access.

As our flagship botany journal, PhytoKeys is part of our concerted effort to help advance taxonomic studies. The more we know about biodiversity, the better we are equipped to protect it.

This is why, in a time when so many species are getting wiped out from the face of the Earth before we even become aware of their existence, it is truly exciting that we can sometimes be the bearer of good news.

Take the story of Gasteranthus extinctus from Ecuador doesn’t its name sound a lot like extinct to you? That’s because the scientists named it based on specimens collected some 15 years earlier. So, they suspected that during the time in between, the species had already become extinct.

Yet, this is a happy-ending story: in a surprising turn of events, the plant was rediscovered 40 years after its last sighting. Gasteranthus extinctus is the hopeful message that we all needed: there’s still so much we can do to protect biodiversity.

Long believed to have gone extinct, Gasteranthus extinctus was found growing next to a waterfall at Bosque y Cascada Las Rocas, a private reserve in coastal Ecuador containing a large population of the endangered plant. Photo by Riley Fortier.

Over the time, we saw some ground-breaking botany research. We welcomed some record-breaking new plant species, such as the 3.6-meter-tall begonia, and the smallest Rafflesia that measures around 10 cm in diameter.

We witnessed the discoveries of some truly beautiful flowers.

Some of them may have looked like they had a demon’s head hiding in them.

We helped unveil some taxonomic mysteries – like the bamboo fossil that wasn’t a bamboo, or the 30-meter new species of tree that was “hiding in plain sight”.

Then there was the overnight celebrity: the first pitcher plant to form underground insect traps.

Published less than two months ago, Nepenthes pudica broke all kinds of popularity records at PhytoKeys: it became the journal’s all-time most popular work, with thousands of shares on social media, more than 70 news outlets covering its story, and upward of 70,000 views on YouTube.

Publishing in PhytoKeys is always a pleasure. I appreciate the quick but rigorous peer review process and reasonably short time from initial submission to the final publication.

says Martin Dančák of Palacký University in Olomouc, Czech Republic, lead author of the Nepenthes study.

Every week, PhytoKeys publishes dozens of pages of quality botany research. Every week, we’re amazed at the discoveries made by botanists around the world. In a field that is so rapidly evolving, and with so much remaining to be unveiled, the future sure seems promising!

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Redefining genera across the legume subfamily Caesalpinioideae in latest PhytoKeys issue

The Special Issue features 16 papers by 54 authors from 13 countries and forms Part 14(1) of the Advances in Legume Systematics Series.

Blog post by Colin Hughes, University of Zurich

The three most important taxonomic ranks used to classify organisms are family, genus and species, especially the latter two, which make up the scientific binomials used to communicate about biodiversity, and indeed about all aspects of biology. While the description of a new plant family is now a very rare event, the same is not true for genera. Indeed, delimitation of genera within many plant families remains in a state of considerable flux, because many traditionally recognized genera do not correspond to evolutionary groups. This causes unwelcome instability in scientific names of species and is why work to delimit genera lies at the heart of much current research in systematic botany.

This is very much the case for subfamily Caesalpinioideae, the second largest subfamily of the legume family, which is the focus of this new special issue of the open-access, peer-reviewed journal PhytoKeys. With around 4,600 species of mostly trees, shrubs and lianas, distributed right across the tropics in rainforests, dry forests and savannas, Caesalpinioideae represent a spectacularly diverse lineage of tropical woody plants.

New analyses of DNA sequences of 420 species of Caesalpinioideae presented here reveal that 22 of the 152 currently recognized genera do not coincide with natural evolutionary groups, i.e., in phylogenetic terms, they are non-monophyletic. The aim of this special issue is to re-define as many of these problematic genera as possible in order to bring them into line with natural evolutionary lineages. To achieve this, nine new genera of Caesalpinioideae are described, five previously recognized genera are resurrected, and three genera shown to be nested within other genera are consigned to synonymy.

Many of the species in these new genera are important, conspicuous, ecologically abundant, and, in some cases, geographically widespread trees in tropical forests. For example, the three species of the new genus Osodendron  are important large canopy trees in tropical rain forests and riverine gallery forests across a broad swathe of west and central Africa. In recent decades these species have been successively placed in different genera including Cathormion, Samanea and Albizia, among others. The neglected generic placement of these African trees has finally been resolved via analyses of DNA sequences, and a new generic home for them has been established.

In contrast, two of the genera newly described in this special issue, Mezcala  and Boliviadendron, each with just a single species, are much more elusive plants occupying very narrowly restricted geographical ranges. Mezcala occurs across just a few square km of the central Balsas Depression in south-central Mexico and Boliviadendron is known from just two interior valleys of the Bolivian Andes. Establishing these two lineages as distinct genera highlights the importance of conserving these globally rare evolutionary lineages.

Choosing names for new taxa is one of the delights and privileges of the practising taxonomist. Derivations of the names of the nine new genera described in this special issue span features of the plants themselves and the locations where they grow, as well as names of fellow legume researchers honoured with genera named in recognition of their contributions. For example, Osodendron is named after ‘Oso’ a food that is prepared in West Africa from seeds of one of the species now placed in the new genus. Mezcala is named for the indigenous Mezcala culture of the Balsas region in Mexico where the genus is found. Boliviadendron is named as such because it is a tree that grows in Bolivia and nowhere else. The new genus name Heliodendron is derived from the Greek helios (sun) and dendron (tree) because it grows in the sunshine state of Queensland in Australia and its flowers are arranged in sun-like globose heads.

Leaves and fruits of the new genus Naiadendron from Amazonian rainforest. Photo by Glocimar Pereira-Silva

Finally, Naiadendron celebrates the Brazilian Amazon where the genus grows, and the famous German botanist Carl Friedrich Philipp von Martius (1794–1868), who named the Brazilian Amazon after the Naiads, Greek mythology’s nymphs of freshwater.

Four of the genera newly described in this Special Issue are named after prominent contemporary legume taxonomists, three women and one man: Gretheria for Rosaura Grether, a Mexican specialist on the genus Mimosa, Ricoa  for Lourdes Rico, another Mexican botanist who worked on legumes based at Kew, Marlimorimia, in honour of Marli Pires Morim of the Jardim Botânico do Rio de Janeiro, Brazil in recognition of her contributions to the taxonomy of mimosoid legumes, and Gwilymia named for Gwilym Lewis, in honour of one of the world’s most experienced and productive legume taxonomists who is legume research leader in the Herbarium at the Royal Botanic Gardens, Kew.

One of the central achievements of the work on Caesalpinioideae presented in this Special Issue is that for the first time a truly pantropical analysis of this large group of plants has been accomplished. A global synthesis is essential to work out how many genera there are.

For example, by sampling across Asia, Africa, Madagascar, North and South America, it has become clear that the Old World species of the important pantropical genus Albizia are not closely related to Albizia in the Americas, prompting splitting of the genus and resurrection of the name Pseudalbizzia for the New World species. All elements of the former Albizia – the last so-called ‘dustbin’ genus in the mimosoid legumes – are accounted for in this special issue (here, here and here). Similarly, the genus Prosopis, one of the most important silvopastoral tree genera of the dryland tropics, has traditionally encompassed elements spanning the New and Old Worlds that are here shown to comprise four distinct evolutionary lineages, two in the Old World and two in the Americas, here treated as four separate genera.

Changes to the scientific names of species are not always immediately welcomed by users, but over time, establishment of a classification that is based on robust evidence about evolutionary history will result in greater nomenclatural stability and in named taxa that are aligned with natural groups and hence biologically more informative. This special issue, reshaping the generic system of a species-rich group of legumes, is an important step towards that goal.

Photo credits: Globimar Pereira-Silva, Steen Christensen, William Hawthorne, Colin Hughes, Luciano de Queiroz, Marcelo Simon.

Guest Blog Post: Researchers split the birdcatcher trees (genus Pisonia) into three

Large Cabbage trees (Pisonia grandis) dominate the landscape of a small island in the Pacific Ocean
Photo by Jean-Yves Meyer (Délégation à la Recherche de Polynésie Française, Tahiti, French Polynesia)

Guest blog post by Marcos Caraballo


The birdcatcher trees – genus Pisonia – are infamous for trapping birds with their super-sticky seed pods that would frequently entangle the body of the ‘victim’. Left flightless, the poor feathered creatures eventually die either from starvation or fatigue, or predators. Similarly notorious are the birdcatcher trees for botanists, who have been baffled by their complicated classification for the last three centuries. 

Here’s why myself and graduate student Elson Felipe Rossetto of the Universidade Estadual de Londrina (Brazil) decided to take up the untangling of this issue with our recent taxonomic studies. You can find our research paper published in the open-access scholarly journal PhytoKeys.

Ripe fruits (anthocarps) of the Birdlime tree (Ceodes umbellifera)
Photo by Ching-I Peng [deceased]

We reestablished two genera: Ceodes and Rockia, where both had been previously merged under the name of Pisonia. Now, as a result, there are three distinct lineages of birdcatcher trees from the islands of the Pacific and Indian Oceans: Ceodes, Pisonia, and Rockia.

“Previous molecular studies on Pisonia species from around the world showed that species were clustered into three major groups, and here we assign names for each of them. With this new classification, a large number of the species known as Pisonia will be henceforth named Ceodes. This includes the Parapara (Ceodes brunoniana) and the Birdlime (Ceodes umbellifera) trees, both native to many islands, including Hawaii and New Zealand. They are commonly planted in gardens for their lush and sometimes variegated foliage, as well as their fragrant white flowers. However, the Cabbage tree (Pisonia grandis) will still be technically known as Pisonia.”

adds the study’s lead author Felipe Rossetto.
Male (staminate) showy flowers of the Birdlime tree (Ceodes umbellifera)
Photo by Joel Bradshaw (Far Outliers, Honolulu, Hawaii)

Birdcatcher trees have generated much controversy in the popular media because of their seed pods (technically called “anthocarps”) secreting a sticky substance that glues them to the feathers of seabirds or other animals for dispersal. Sometimes, though, too many seed pods can harm or kill birds, especially small ones, by weighing them down and rendering them flightless. This macabre practice has led to many controversies and local campaigns aiming to remove the trees, even illegally.

Brown noddy (Anous stolidus) covered with the sticky fruits (anthocarps) of the Cabbage tree (Pisonia grandis)
Photo by Jean-Yves Meyer (Délégation à la Recherche de Polynésie Française, Tahiti, French Polynesia)

In spite of their forbidding reputation, however, we would like to stress that birdcatcher trees have positive effects on ecosystems and are important components of vegetation, especially for small islands. Sadly, there are many endemic and already endangered species of birdcatcher trees that only exist on a few small islands, where they are effectively placed at the mercy of local people.

Many species of birdcatcher trees are large and, thereby, tolerate harsh environments like seafronts and rocky cliffs, making them prime nesting spots for seabirds. Birdcatcher trees are also ecologically curious and could be regarded as keystone species in small islands, because their soft branches can sustain many types of invertebrates; their flowers are an important food source for bees and ants; their dense leaf litter nourishes the soil; and their roots have intimate interaction with native underground fungi (mycorrhiza).

All in all, clarifying the taxonomy of the birdcatcher trees is the first step to understanding how many species exist and how they relate to each other. 

Although most people relate birdcatcher trees with beaches and coastal habitats, there are species that are only found in mountains or rainforests. For example, the species now allocated to the genus Rockia is endemic to the Hawaiian archipelago. These are small trees able to grow in dry to mesic mountain forests. Using our new classification, future studies can explore in detail the hidden diversity of these enigmatic plants, and find out how trees with high dispersal capabilities evolve into species endemic to small island ecosystems.

Cabbage trees (Pisonia grandis) are important components of the vegetation in small islands due to their massive size
Photo by Jean-Yves Meyer (Délégation à la Recherche de Polynésie Française, Tahiti, French Polynesia)

About the author:

Marcos A. Caraballo-Ortiz is a research associate at the Smithsonian Institution (Washington, D.C., United States). His research interests include plant systematics and ecology, with a focus on flora of the Caribbean Islands. Dr. Caraballo-Ortiz has experience studying the taxonomy of several groups of tropical plants, with a particular interest in neotropical Mistletoes (Loranthaceae, Santalaceae, Viscaceae) and the Four O’Clock family (Nyctaginaceae). 

For more information about his projects, visit marcoscaraballo.com.

Research paper:

Rossetto EFS, Caraballo-Ortiz MA (2020) Splitting the Pisonia birdcatcher trees: re-establishment of Ceodes and Rockia (Nyctaginaceae, Pisonieae). PhytoKeys 152: 121-136. https://doi.org/10.3897/phytokeys.152.50611


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