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


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.

Follow PhytoKeys on Twitter and Facebook for live updates and news across Kingdom Plantae.

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

Described 28 years post-collection, new grass species makes a strong case for conservation

Originally collected 28 years ago in Ecuador, new species Poa laegaardiana has been just described, only to find out its prospects for surviving in its type location seem bleak nowadays. The study was published in the open access journal PhytoKeys.

When roaming in the Cordillera de los Andes of Ecuador, near the village of Facundo Vela, little did Smithsonian scientist and author, Dr. Paul M. Peterson, know that a small grass specimen will not only turn out to be an intriguing new species, but will also make a big statement on the importance of conservation.

Scientific drawing showing what makes new species P. laegaardiana distinct from its congeners

Almost three decades after its original collection the new species P. laegaardiana has finally emerged from its herbarium collection, but the story took an unexpected twist.

It took the authors a single Google Earth search to find out that what used to be the natural habitat of the newly found densely tufted bunchgrass, is now occupied predominantly by small farms.

Heavy agricultural use of the terrain, poses a good possibility for P. laegaardiana to have already been extirpated from this location. With the species currently known only from this area, chances are that this newly described species, might in fact turn out to be already extinct.

“Further studies are needed to search the area and browse collections for specimens from different locations,” explains Dr. Peterson. “But, in fact, it may well be that with our study we are documenting a possible extinction of a species, happening in the space of just 30 years. The story of P. laegaardiana serves to show how human-induced habitat loss can indeed be a major threat to the survival of life on Earth.”

The new species was named after renowned Danish botanist Simon Laegaard, who has made extensive collections in South America, Greenland, Ecuador, and Bolivia (accompanied by the authors) contributing to the documentation of the flora to make informed conservation and management plans.

Google Earth image comparison between the area of collection in 2011 and today. With the area having been plowed, chances of the grass still existing there are small, however it may still be found along the margins of the fields. CREDIT Left: @2018DigitalGlobe; Right: @2018Google @2018CNES/Airbus

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Original Source:

Peterson PM, Soreng RJ (2018) Poa laegaardiana, a new species from Ecuador (Poaceae, Pooideae, Poeae, Poinae). PhytoKeys 100: 141-147. https://doi.org/10.3897/phytokeys.100.25387

Cost-benefit analysis of strategies against severely harmful giant hogweed in Germany

While invasive species are considered to be a primary driver of biodiversity loss across the globe, species such as the alien for Germany giant hogweed pose even greater risks, including health hazards to humans, limited accessibility to sites, trails and amenity areas, as well as ecological damages.

Since 1st January 2015, EU member states are obligated to develop concrete action plans against (further) spread of invasive alien species. In order to do so, however, policymakers need adequate knowledge about data of the current spread situation as well as information about costs and benefits of control measures. Therefore, German researchers analyse the present situation and control measures, as well as the cost-effectiveness of the possible eradication strategies. Their analysis is published in the open access journal NeoBiota.

Largely spread across Germany, the giant hogweed (H. mantegazzianum) grows in a wide range of habitats, including roadsides, grasslands, riparian habitats and woodland margins. The highest invasion percentage (18.5%) was found for abandoned grasslands, field and grassland margins, and tall-forb stands.

While the species poses a serious threat on native biodiversity through competitive displacement of native plants, it is particularly dangerous to human health. Its watery sap contains several chemical agents. In contact with the skin, this sap can cause severe blistering if the person is simultaneously exposed to sunlight. Furthermore, the hypersensitivity of the skin towards sunlight may persist for a number of years. Additionally, the giant hogweed can limit public accessibility to sites, trails and amenity areas, as well as inflict ecological damages, such as erosion at riverbanks.

In order to provide policymakers with the information needed for adequate control measures, Dr. Sandra Rajmis from the Julius Kühn-Institute, Dr. Jan Thiele from the University of Münster, and Prof. Dr. Rainer Marggraf from Georg-August-Universität Göttingen examine costs and benefits of controlling giant hogweed in Germany.

To address these challenges, the scientists firstly study the present state and costs of control measures, based on survey data received from German nature authorities. Then, they analyse the identified control options in terms of cost effectiveness with regard to the invaded area types and sizes in the infested German districts. To estimate the benefits of the eradication strategies, they turn to a choice experiment survey conducted in German households.

“Only in light of these findings, policymakers can properly understand about the societal costs and benefits of alternatives and decide about societal favored control options in Germany,” point out the researchers.

The team also notes that cost-effectiveness of eradication strategies depends on the length of the period over which they are implemented and observed.

“As this is the first cost-benefit analysis estimating welfare effects and societal importance of giant hogweed invasion control, it could serve as guideline for assessments of eradication control in other European countries and support the implementation of the EU directive 1143/2014,” they conclude.

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Original source: Rajmis S, Thiele J, Marggraf R (2016) A cost-benefit analysis of controlling giant hogweed (Heracleum mantegazzianum) in Germany using a choice experiment approach.NeoBiota 31: 19-41. doi: 10.3897/neobiota.31.8103

Poorly known South African mountain endemic appears to be a very valuable keystone species

Mountain ecosystems are valuable providers of key resources including water. These ecosystems comprise diverse species, some of which appear to be especially important to the ecosystem’s functioning. In poorly studied mountain environments in biodiversity-rich countries, these keystone species can often be overlooked and undervalued.

Macowania is a group of yellow daisy shrubs occurring in the alpine-like regions of the Drakensberg and highlands of Ethiopia, Eritrea and Yemen. Doctoral student Joanne Bentley, University of Cape Town, studied the genetic relationships between the various Macowaniaspecies and relatives during her Masters degree studies. Her research led to the first collection of the poorly known species Macowania revoluta (known also as the Amathole Macowania) in about 40 years.

The story of Macowania revoluta is published in the open access journal PhytoKeys.

The Amathole Macowania appears to be an exceptionally important keystone species. This is because it forms one of the dominant members of the valuable mountain wetland communities and, thus, likely plays a very important role in wetland functioning and soil protection.

It appears to be somewhat tolerant of woody alien species and a valuable pioneer species protecting its native co-habitants. Plants like this one buffer more sensitive plants from sudden changes in environment (such as forestry, alien invasion and fire), and provide an opportunity for the ecosystem to ‘bounce back’.

113693Restricted to the Amathole mountains in the Eastern Cape Province, South Africa, the Amathole Macowania was first collected sometime before 1870 by the pioneer botanist Peter MacOwan, and was well documented until around 1949. After that, except for one record in 1976, the plant quietly disappeared.

“This was the first Macowania species that we found during our fieldtrip across the greater Drakensberg. We had combed several of the localities where it had been collected before; mostly from several decades ago, some from more than a century ago!” says Joanne Bentley. “We became increasingly doubtful about finding the plant, given the heavily transformed plantation landscape.”

“Ready to throw in the towel, we came across a peaty area on the margins of the forest and decided on one last investigation. We were lucky: it was growing prolifically! It was a very special moment.”

As it often happens, exciting discoveries come in bulk. Joanne’s discovery of the plant in July 2010 was followed by another record in October 2010, by the Curator of the Schonland Herbarium, Tony Dold. In 2014 at least three additional localities were recorded along the popular Amathole Hiking Trail by Dr Ralph Clark, Rhodes University. A further record was added in 2015 by Vathi Zikishe, South African National Biodiversity Institute. The verdict: this is a very localised but patchily abundant species, and an ecologically valuable component of the Amathole flora.

Listed as ‘Data Deficient’ in the Threated Plants List for South Africa, this string of modern records of the species also provided the first opportunity to get an idea of its ecology and abundance, as well as the first photographs.

“The practical value of this species in local land restoration projects still needs to be explored, but the opportunities are exciting,” says Dr Clark. “The discovery that this obscure endemic mountain plant is not only abundant, but is, in fact, fulfilling an extremely important ecological role, highlights the value of detailed mountain biodiversity research in southern Africa.”

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Original source

Clark VR, Bentley J, Dold AP, Zikishe V, Barker NP (2016) The rediscovery of the Great Winterberg endemic Lotononis harveyi B.-E.van Wyk after 147 years, and notes on the poorly known Amathole endemic Macowania revoluta Oliv. (southern Great Escarpment, South Africa). PhytoKeys 62: 1-13. doi: 10.3897/phytokeys.62.8348