6 February 2024

The science behind the festival: orchids of Madagascar

Explore the captivating world of Madagascar's orchids, from Darwin's iconic species to vital conservation efforts as we unveil the science and beauty behind these unique and vulnerable plants.

A vibrant green forest with large palm like trees

Orchids have captivated humanity since the dawn of civilisation. They can be found on almost every continent on Earth, exhibiting some of the most exquisite morphological adaptations in the plant kingdom. Of the iconic orchids in history, maybe one of the most well-known, the Darwin’s orchid, is endemic to Madagascar. 

Both orchid enthusiasts and scientists and even the public often associate Madagascar with orchids. The island houses many amazing orchid species, most known for their horticultural and ornamental value. However, some of them are also locally and globally important sources of food

Madagascar is the world’s largest exporter of vanilla, producing around 40% of the world’s vanilla. Aside from the globally known and celebrated vanilla, Jumellea fragrans is also locally used to flavour a traditional rum on Reunion Island. 

Madagascar is one of the world’s most diverse and distinctive orchid floras, with over 1,000 species (amounting to around 10% of all plant species in Madagascar), of which 90% are known to occur only there. 

A bee orchid flower with pink petals and a rounded dark lip on the lower side
Bee orchid (Ophrys apifera), Bernard DuPont on Wikimedia Commons CC BY-SA 2.0

The high diversity and endemism for the Malagasy orchids is truly paramount, with the country being home to around 4% of all known orchids. However, the very restricted distribution of many Malagasy orchids makes them particularly vulnerable to habitat change and loss. This is especially relevant since most of the population of Madagascar lives by subsistence farming.  

These factors have caused the decline of several orchid species in the country. Luckily, since 2015, Kew has been working very hard on the in-situ conservation of Malagasy orchids, coupled with the reintroduction of selected species. 

Kew’s connection to Madagascar runs even deeper, with a team of 40 Malagasy staff members at the Kew Madagascar Conservation Centre (KMCC) working tirelessly to understand and conserve the Malagasy Flora and Funga. 

So, for our annual orchid festival, we’ve chosen Madagascar to highlight our long-term commitment to understanding and conserving the Malagasy Flora by showcasing the diverse, contrasting and intricate beauty of orchids

Collage of native flora and fauna of Madagascar
Orchids 2024 © RBG Kew

Unsurprisingly, orchids have been heavily featured in our Science Collection Digitisation Project. So join us on this trip highlighting how Kew has played a crucial role in helping ensure the orchids of Madagascar will be appreciated by generations to come.

The land before time 

The island of Madagascar is situated in the Indian Ocean about 400 km east of continental Africa, below the equator, with the southern part of the island running through the Tropic of Capricorn. This grants the country its amazing tropical to subtropical climate, which, together with the island’s unique geography and geology, serve as fertile soil for evolution

On top of that, Madagascar separated from the mainland about 165 million years ago, during the Middle Jurassic. That means that Madagascar’s biodiversity began taking a very independent path during the same period ichthyosaurs and pliosaurs dominated the seas, pterosaurs were the dominant flying vertebrates, and the titanic sauropods and ferocious megalosaurs roamed the Earth. 

A shot showing curvature of the earth and the island of madagascar
Madagascar, as photographed by an Expedition 56 crew member on the International Space Station, NASA

With this in mind, it makes sense that 9 of every 10 plant species native to Madagascar are unique. Inspired by the uniqueness and beauty of Madagascar’s biodiversity, Orchids 2024 celebrates the striking contrasts that encapsulate this bright and tropical country. 

Across the ten unique climatic zones within the Princess of Wales Conservatory, you can see elements and inspiration from the spiny forests to succulent woodlands, together with a menagerie of the most unique wildlife on Earth (don’t miss the extraordinary giraffe weevils!)

The orchid that puzzled Darwin 

A Malagasy orchid made such a massive impression on Darwin that it is popularly known as Darwin’s orchid. Angraecum sesquipedale is indeed puzzling with its mindboggling nectar spur that can reach up to an impressive 45 cm long! Unsurprisingly, Darwin was perplexed by how deep inside the spur the nectar was and how a pollinator could possibly reach that nectar!  

Based on the flower’s characteristics (white colouration, strong scent produced only at night, no place for a pollinator to land/perch/ and a very narrow nectar spur), Darwin correctly hypothesised this species to be pollinated by a yet undescribed species of hawkmoth. 

A close up on two creamy white orchid flowers
Darwin's orchid (Angraecum sesquipedale) flower, Andrew McRobb © RBG Kew
A long green spur of a orchid
Darwin's orchid (Angraecum sesquipedale) spur, sunoochi on Wikimedia Commons CC BY 2.0

These amazing moths are nocturnal and different from other moths and butterflies, they do not perch when visiting a flower, doing so while in flight. Hovering while visiting flowers is something hummingbirds excel at, which has caused hawkmoths to be also known as hummingbird moths in some places. 

Darwin’s hypothesis received strong support almost 45 years later when Xanthopan morganii praedicta was discovered and described, with its huge proboscis (butterfly tongue) that could exceed 20 cm. However, it wasn’t until 1992, 130 years later, that Xanthopan morganii praedicta was observed feeding on the flower. 

The long tongue of Xanthopan morganii praedicta is seen on a dried specimen of the insect
The long tongue of Xanthopan morganii praedicta allowed it to reach the nectar of Angraecum sesquipedale © Nesnad

Unfortunately, Darwin did not live to see the incredible pollinator he had predicted, let alone see hard evidence of its exceptional interaction with A. sesquipedale. This has only added to the lore around plant and pollinator, with both being often depicted together and serving as the most iconic example of evolution. 

In a similar way as the finches were crucial in helping Darwin develop and mature his theory of evolution by natural selection, this orchid served as an example of co-evolution resulting from a mutually beneficial relationship. 

Birds of a Feather 

Another interesting orchid/animal connection refers to another Madagascar endemic orchid recently described as new to science by Kew botanists. The tiny orchid Aeranthes bigibbum spends its entire life on top of trees from a tiny patch of forest in Madagascar. 

With its small, white star-shaped flowers, this unusual new species was only discovered and saved from certain extinction by the combined efforts of Kew and Malagasy botanists working in partnership with a small group of villagers. 

A hanging orchid has two large flowers with unevenly shaped large petals ending in hairlike structures
Aeranthes bigibbum © RBG Kew Johan Hermans

Said villagers came together to create and manage a small forest reserve to protect the rare and Endangered helmet vanga (Euryceros prevostii). Visitors from around the globe flock to the reserve with the chance to see the stunning blue-beaked bird. 

Without the helmet vanga, it is very likely that the forest where Aeranthes bigibbum occurs would have been cut. This goes to show that caring for a single species can protect countless others in what is called the umbrella effect, where the conservation of an iconic and charismatic species can benefit an entire ecosystem.  

Going digital 

Botany is not always flowers and lush tropical forests. Unfortunately, despite fieldwork being a crucial and very appealing aspect of a botanist’s job, most of our time is actually spent working inside herbaria (the plural for herbarium, a collection of dried and pressed plant specimens). 

For that matter, we house one of the world’s five largest herbarium collections, including an estimated 7 million dried plant specimens. Herbarium collections serve as priceless repositories of biological knowledge. They can help scientists understand species’ distribution, ecological requirements, how they were affected by pests and diseases, etc. 

Timelapse of Kew Digitisers digitising specimens

However, science is carried out around the globe, most of it currently by scientists who live outside the Global North. For most scientists, travelling the globe to study plant specimens (fresh or dried) is more of a dream than a reality due to financial and political limitations. 

Historically, our collections have remained mostly inaccessible to anyone outside the UK. This is a recurring scenario around the globe, with only around 16% of the over 1.1 billion specimens housed in natural history museums and herbaria being available online. 

As one of the most important botanical institutions on the planet, we’ve made it a key priority to digitise our collections, making them available to anyone with an internet connection. This effort will accelerate research into global issues, helping protect our planet for future generations and make science more accessible and inclusive. 

Digitiser holding barcoder to digitise specimen as part of Kew's Digitisation Project

You can now immortalise a piece of botanic history. Donate to digitise a plant today and help us unlock nature's secrets.

Digitisation encompasses way more than just providing digital access to specimens. Digitising Kew’s Orchid Herbarium really represents a unique opportunity, not only to be so close to so many plants and historical records, but to also help preserve nature. 

Make sure to visit our Orchid Festival, as well as the Orchids After Hours event, now aware of the importance of the science behind the beauty and art. Also, in case you want to learn more about orchids while contributing to our Digitisation Project, we are always in search of volunteers to help us decipher and transcribe specimen labels on DigiVol.

We currently have a fantastic DigiVol expedition on the Orchids from Colombia and Panama, with many others (on orchids and other plants) available and continuously uploaded.

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