This is the world’s biggest and weirdest flower. Can Pinoy scientists save it?

MIKAEL ANGELO FRANCISCO

On June 16, 1841, with a roomful of scientists as his audience, museum curator J.E. Teschemacher revealed a new species of Rafflesia, a parasitic plant genus that was only formally established twenty years earlier. Teschemacher based his description on three specimens from Samar, an island in the Philippines. The samples, which were sent to his office at the Boston Museum of Natural History, were buds that had yet to reach full maturity. This meant that he missed significant details that a full-grown flower could have provided.

But what Teschemacher lacked in evidence, he made up for in confidence. He compared the buds in his possession to Indonesia’s R. arnoldii and R. patma — the only other Rafflesia species with comprehensive descriptions accessible to him at the time — and observed that they were considerably smaller than the former and lacked the spore-containing cavities of the latter. Per Teschemacher’s assessment, these differences were enough to give the buds a species name of their own: Rafflesia manillana, referencing the capital city of their country of origin.

There was just one small issue, which Teschemacher himself noted: An English collector, Hugh Cuming, had obtained samples of the same plant from the same area in 1838, and had sent them to Scottish botanist Robert Brown for review. Curiously, Teschemacher added this clarification in his paper: “Although I propose the specific name of Manilana [sic] for this species, I would readily yield it to any other [that Cuming] may wish to retain.”

In response, Brown proposed that the species be called R. cumingii in his 1844 paper. Dismissing Teschemacher’s “trivial” name suggestion, Brown asserted that the new Rafflesia should instead be named “in honour of the discoverer.” But as time passed, other experts in the field concluded that Brown only pushed the R. cumingii name “to bring it in line with the others named after people” — and so, R. manillana became the species’ official name.

For the remainder of the 1800s, three other Rafflesia species were identified from the Philippines. And then, after 1885… nothing, for a very long time. In fact, it took a staggering 117 years before another Philippine Rafflesia species was discovered: R. speciosa, in 2002.

Since then, Filipino scientists have taken a noticeably proactive stance in studying and conserving the world’s most peculiar plant — one that has largely remained a botanical mystery for more than two centuries.

An open flower of R. speciosa, about 40 cm, with its carrion fly pollinator. (Photo: J. Molina)

The entire Rafflesia genus is an enormous enigma, in more ways than one.

Each Rafflesia plant bears a single, massive flower, often brown or red with white spots. (Even the smallest species in the genus, the Philippine endemic R. consueloae, has doughnut-sized blooms.) Typically paired with each blossom’s maroon color is a miasmic odor, along with an internal structure that mimics animal fur and even the ability to generate its own heat. As a result, the foul-smelling, five-petaled flower becomes bizarrely evocative of death and decay. It’s no wonder that the largest species, R. arnoldii — which produces the biggest individual flower on the planet — is also called the “corpse flower” or “corpse lily.”

The conspicuous components of Rafflesia are already hard to miss. But what’s even more difficult to ignore is everything we don’t see: Every member of this genus has no stems, no shoots, no leaves, and no roots. Rafflesia species are endoholoparasites, meaning they possess two key traits. They quietly infect their host plants (certain species of Tetrastigma grapevines) and remain hidden until they’re ready to emerge. Additionally, they rely on their hosts for their carbon needs, as they are incapable of photosynthesis.

It’s easy to wonder why or how Rafflesia species grow to be so enormous, or if they could even really be counted as plants in the first place. Experts have proposed some plausible answers to the first question. Some suggest that their size helps them attract pollinators; others say that they only grow as big as their hosts allow them to, as far as both sustenance and structural integrity are concerned. In colloquial terms, this could either be a feature or a bug.

Still, for something that has been known by science for more than two hundred years, information about Rafflesia is oddly scarce, despite it being such a fascinating genus. “I think it’s because not many scientists have the patience and resources to undertake Rafflesia studies,” shared Dr. Jeanmaire Molina, a plant evolutionary biologist and associate professor at Pace University in New York. Molina emphasized that Rafflesia species are notoriously challenging to observe, obtain, or grow outside of their remote forest habitats in Southeast Asia.

The fact that Rafflesia plants are so difficult to study means that there is much about them that we don’t know yet — and thus, much to learn about them. For example, experts can’t say for sure why Rafflesia species are only known to thrive on some (not all) Tetrastigma vines. What makes this even more baffling is that the plant family to which Rafflesia belongs evolved as early as the Cretaceous, way before Tetrastigma did. In other words, it’s likely that now-extinct vine species served as prehistoric Rafflesia hosts — and for some reason, only Tetrastigma vines fulfill that role today. This is one of the questions that Molina is currently investigating; based on previous research, she suspects that ecological factors may be involved, and that only Tetrastigma species with a particular chemistry and microbiome can be suitable Rafflesia hosts.

“It is not clear what is special about them, but that is obviously going to be an interesting area of research,” according to Dr. Michael Purugganan, Silver Professor of Biology at New York University’s Center for Genomics & Systems Biology.

Rafflesia fruit cut open to reveal its extremely tiny seeds, each less than a millimeter in size; each fruit is said to contain millions of seeds. (Photo: J. Molina)

In 2014, Molina and Purugganan were part of a team that co-authored a paper about the possible loss of the chloroplast genome in Rafflesia, a finding that made sense given Rafflesia’s inability to produce carbon dioxide on its own. Recently, the two worked with a different set of scientists spread across four countries (Canada, Indonesia, the Philippines, and the United States) on another pioneering Rafflesia study. Published in the open access journal Plants People Planet, it involved assembling a transcriptome (a set of RNA transcripts from the genome) of R. speciosa seeds for the first time. The team created the transcriptome from scratch, using RNA they extracted from the seeds. They then compared the transcriptome with four other plants — Arabidopsis, Cuscuta, Striga, and Anoectochilus — in order to gain new insights on Rafflesia’s biological processes.

“Arabidopsis is the quintessential model plant, and much of what we know of plant genetics came from studies of this plant,” explained Molina, the lead author of the study. “Cuscuta and Striga are other plant parasites whose seed transcriptomes have been characterized, while Anoectochilus is an example of a mycoheterotrophic orchid whose seed transcriptome has also been published.” Similar to holoparasites, mycoheterotrophic plants rely on hosts (in this case, fungi) in order to meet their full or partial energy needs.

As it turns out, Rafflesia’s genetic and metabolic seed pathways resemble those of the other plants, but with a couple of twists. For one, it appears that Rafflesia, Cuscuta, and Striga evolved similar characteristics as parasitic plants, despite not being closely related — an example of convergent evolution, suggesting that they gradually developed those traits to ensure the survival of their respective genera.

Additionally, they found no significant traces of genes involved in fungal symbiosis in the Rafflesia transcriptome. “As someone who studies the genetics of evolution, you always want to see if biological processes that do the same thing in different species are encoded by the same genes,” said Purugganan. “In this case, even though superficially the symbiosis of fungi with plants looks similar to Rafflesia and Tetrastigma, they seem to be using different genes – which means that symbiosis can evolve in different ways in different sets of organisms.”

The team also found evidence of a gene in Rafflesia that was possibly obtained from Tetrastigma — specifically, one associated with the vine’s internal defenses. This process of horizontal transfer, or the passage of genetic information from one organism to another sans sexual reproduction, is commonly seen in bacteria and certain single-celled organisms, but not in plants. Thus, one can think of Rafflesia as a Trojan horse, successfully bypassing the host’s immune system by making itself appear, on a genetic level, that it belongs there. As Molina put it, some consider it a kind of “genomic camouflage or mimicry.”

Interestingly, the paper was published with two abstracts: one in English, and one in Filipino, the Philippines’ national language. “This research would not have been possible without my Filipino collaborators in Miagao, Iloilo, and as a gesture of my immense gratitude, I decided to include a Filipino abstract,” explained Molina, who added that to her knowledge, this was the first instance of an internationally published scientific study with a Filipino abstract. For Purugganan, this makes the study easier to understand for Filipinos, and “highlights this study as a Filipino work.”

Team photo when the Rafflesia seeds were collected, next to an open Rafflesia speciosa flower. (Photo: J. Molina)

One could say that the challenge of Rafflesia conservation is as gargantuan as the plant’s world-famous flowers. So monumental is the task, in fact, that out of the many efforts to grow the genus ex situ (outside of its natural habitat), very few have truly accomplished it.

“Bogor Botanical Garden in Indonesia achieved success after 6 years — it took 6 years before they saw their R. patma plants bloom, and another 3 years to see new buds,” shared Pastor Malabrigo, a professor from the Department of Forest Biological Sciences at the College of Forestry and Natural Resources (CFNR) of the University of the Philippines Los Baños (UPLB). “It is particularly difficult for Rafflesia plants [to be grown ex situ] because we know very little about them in terms of seed biology and propagation techniques.”

Along with CFNR-UPLB teaching associate Adriane Tobias and Oxford University’s Dr. Chris Thorogood, Malabrigo went on an educational trip to Bogor in November 2022. There, they not only observed the growth of Bogor’s Rafflesia plants, but also learned about the process of ex situ propagation by grafting, the sole technique that worked for the institution after two decades of experimentation.

To the average person (or perhaps, to someone with a green thumb), the process may sound simple and straightforward. As Malabrigo detailed, it involves obtaining a Rafflesia-infected Tetrastigma vine, and then grafting it onto an uninfected Tetrastigma vine elsewhere as its scion. Malabrigo also emphasized that transporting the infected Tetrastigma sample should not take more than 24 hours: “The longer it takes to graft the plant, the lower the chance it will survive.”

Malabrigo and his colleagues opted to use a different species — R. panchoana, from Mt. Makiling in Luzon — due to its close proximity to the grafting site at the UP Land Grant. Since both Mt. Makiling and the Land Grant fall under the jurisdiction of UPLB, it made the process of obtaining the necessary paperwork much easier.

In addition, R. panchoana has a shorter reproduction cycle than R. patma. “We hope that this endeavor will be successful and that we will see the fruits of our labor in two years,” said Tobias, who described his interest in Rafflesia as something that has transformed into both a personal advocacy and a passion project. “This process is still a mystery, as is the complete development of Rafflesia from growing inside the vine to producing buds and blooming flowers.”

The Banao protected landscape. (Photo: A. Tobias)

Non-scientists tend to perceive the words “parasite” and “predator” in a negative light. However, these organisms play crucial roles in the ecosystems where they thrive — and the parasitic Rafflesia is certainly no exception.

“[Parasitism] is a process that is essential in maintaining ecosystem balance, ultimately increasing species diversity in an ecosystem,” explained Molina. “The parasite keeps the host population in check, preventing overgrowth that can negatively impact other species and reduce diversity.” She added that Rafflesia fruits and seeds serve as food sources for ants and small mammals, who in turn act as the plant’s dispersal vectors, transporting seeds to different areas in their shared habitats. For Molina, this is enough to consider Rafflesia plants as “keystone species” in their ecosystems.

Tobias mentioned the “intricate relationship” that Rafflesia plants share not only with their hosts, but also with their pollinators. To carrion flies, Rafflesia are like rotting animal corpses on the forest floor; in other words, irresistible. “The floral chamber is designed to trap the carrion flies, increasing the duration of their visit and the likelihood of contact with the stigma or pollen-producing anthers,” said Tobias, who also noted that the monstrous flower is an apt breeding site for pollinators.

Researchers doing fieldwork in the Banao protected landscape. (Photo: A. Tobias)

In Indonesia, Rafflesia plants are believed to have aphrodisiac properties, and they are incorporated into tonics, energy drinks, and fertility supplements for women. Some even boil Rafflesia buds, using the resulting broth as a remedy for fever, headaches, and body aches. Experts have also documented the use of Rafflesia in traditional medicine in Poring, Sabah.

Interestingly, in the Philippines, the lack of general knowledge about Rafflesia may have served as equal parts boon and bane for the conservation of the genus.

“Indigenous communities believe that Rafflesia possess bad spirits, and that something bad will happen to you if you touch them,” Malabrigo shared. This became quite apparent to him when he discovered a new species, R. banaoana, in the forests of Banao, Kalinga. He recalled having a hard time convincing the local townsfolk to help him collect samples for study and publication. “But then, this does help conserve Rafflesia species, since naturally, nobody wants to disturb them.”

Since Rafflesia varieties in the Philippines are notably less pungent than varieties in other parts of Southeast Asia, Malabrigo speculated that the “haunted flower” idea may have originated from its unique appearance — that, and the fact that it seemingly grows from out of nowhere. “Imagine the townsfolk suddenly seeing this ginormous flower that’s unfamiliar to them. Perhaps they steer clear of the flowers not because of the odor, but because they think, ‘Hey, this flower looks strange — it probably has a strange guardian, or a strange creator.”

That’s not to say, of course, that indigenous groups are completely ignorant when it comes to Rafflesia. “They’re the ones who have experience with the species and are associated with it, not us. Even we scientists learn a lot from the natives, the locals.” Still, there is limited understanding about the significance of Rafflesia in the Philippines, with most of it coming from anecdotal observations from fieldwork.

Sadly, inadequate familiarity with Rafflesia has led some Filipinos to mistake it for an unrelated but similarly stinky genus, Amorphophallus — and their disdain for the foul-smelling flower reportedly drives them to intentionally destroy known Rafflesia sites, such as those in the Mts. Banahaw-San Cristobal Protected Landscape. Others with good but ultimately misguided intentions pluck Rafflesia flowers from their natural habitats to grow them elsewhere, completely unaware that the endeavor itself is a tremendous challenge even for botanical experts.

Bolos Point, where R. leonardi was found. (Photo: A. Tobias)

Currently, there are 15 endemic Rafflesia species in the Philippines recognized and accepted by Plants of the World Online, a digital database of international flora curated and maintained by the United Kingdom’s Kew Royal Botanic Gardens. This is the largest number of unique Rafflesia species in a single country. Tragically, all Philippine Rafflesia species are narrowly distributed — and teetering dangerously close to extinction.

Regardless of how desensitized we may have become after hearing it so frequently, “endangered” is not a word that scientists and conservationists throw around lightly. Red List assessors like Malabrigo follow a specific set of criteria to determine the conservation status of a given species, including how much of its known habitat areas have diminished and the rate at which its population has decreased. With such data, conservationists can reasonably assess just how threatened a species’ population is.

One particular endemic Rafflesia, R. schadenbergiana, had no recorded sightings for more than a hundred years, and was thought to have gone extinct. However, an unexpected sighting in the 1990s led to the rediscovery of the largest Philippine Rafflesia — a species that “literally is back from the dead,” as Molina put it — in a handful of areas across the island of Mindanao.

For a time, experts couldn’t agree if the Philippines actually had 15 or 13 Rafflesia species, with some arguing that R. camarinensis was simply a synonym of R. baletei, and that R. banaoana was just a variant of R. leonardi. And while the average person may view these as mere displays of scientific pedantry, distinguishing species can have a tremendous impact on conservation strategies.

According to Tobias, if a critically endangered species is declared a synonym of a species that is relatively well distributed, the geographic range of both species appears larger — and it becomes more likely that they’ll be deprioritized in terms of conservation efforts. Meanwhile, Malabrigo had a more succinct explanation:  “If the identity of the species you are studying isn’t clear to you, then your efforts will go nowhere.”

Researchers exploring Bolos Point. (Photo: A. Tobias)

At present, there is no law in the Philippines designed specifically for Rafflesia conservation, but there is an administrative order offering blanket protection for all threatened Philippine plant species.

In 2017, the Department of Environment and Natural Resources (DENR) issued AO 2017-11. It contains a list of recognized threatened plant species in the Philippines (including 12 of the Rafflesia species known to exist in the country at the time) and prohibits anyone from collecting or trading them. Section 4 of the document states that all other native plants absent from the list — such as the other endemic Rafflesia species we now know about — are “non-threatened,” while section 8 promises that the existing list shall undergo regular review. As of this writing, the six-year-old list has yet to be updated.

“Although there is no species-specific conservation program at the national level, some local government units along with the DENR City Environment & Natural Resources Office (CENRO) have declared critical habitat areas where Rafflesia species are occurring, in sites that are not covered by the Protected Areas system in the county,” clarified Tobias.

Still, compared to countries like Malaysia — which has conservation programs and initiatives to increase the involvement of indigenous groups in Rafflesia conservation — there is plenty of room for improvement for the Philippines, especially considering how it’s the world’s center of Rafflesia diversity.

“We are lagging behind when it comes to conservation,” lamented Malabrigo, who added that his team recently submitted a paper — a collaboration among the countries with Rafflesia species — that aims to establish “a network of Rafflesia conservation.”

The teams behind mapping the Rafflesia transcriptome and the Philippine Rafflesia ex situ project have also been talking about ways to collaborate. “We all have the same goal, to propagate and ultimately conserve Rafflesia,” said Molina. “Their success is my success, and vice versa — either way, a triumph for Philippine biodiversity.”

Researchers posing with R. banaoana. (Photo: A. Tobias)

According to Malabrigo, the enigmatic Rafflesia has the potential to become the flagship flower for plant conservation and achieve the same iconic status the giant panda holds for animal conservation. But this can only happen with increased awareness about these massive, mysterious blossoms. “The Philippines is the center of Rafflesia diversity — but so very few even know that we have Rafflesia here.”

Malabrigo hopes to someday see Rafflesia become as prominent in the Philippines as it is in Indonesia, where its image can be seen in schools, offices, hospitals, and even on native clothing. “It’s one of Indonesia’s national flowers — they really take pride in their Rafflesia species. That’s what the Philippines lacks.”

Purugganan expressed a similar view: “[Dr. Molina] convinced me that if there was one charismatic plant group in the Philippines, it was Rafflesia, and it deserves to be studied as an icon of Philippine plant biodiversity.”

“As a plant biologist, I have always been fascinated by Rafflesia because it is a plant unlike any other; it defies almost everything we know about plants,” Molina asserted. “To lose any of our endemic Philippine Rafflesia species is a catastrophic loss not just to Filipinos but to the world; they are evolutionary marvels at least 50 million years in the making that can never be replaced.”