Orchids inspired Darwin and indicate environmental degradation – 03/02/2024 – Science

Every year, Kew Gardens — the London Botanical Garden, in the United Kingdom — holds an orchid festival with a specific theme.

In the 2024 edition, the event’s curators decided to pay homage to Madagascar. The artists used more than 5,000 orchids and other organic materials to create sculptures, arches and arrangements that illustrate the fauna and flora of this African island.

Along with other press outlets, BBC News Brasil had access to the greenhouse where the pieces were assembled before the exhibition opened to the public.

On the occasion, scientists responsible for caring for and studying these plants also shared the most curious scientific facts about orchids.

One of these flowers, for example, served as an inspiration (and ordeal) to the famous English naturalist Charles Darwin.

Another species from this same family provides one of the most appreciated condiments in gastronomy: vanilla.

And orchids can also be the main indicators of the health and balance of a given environment.

Check out the details about these and other curious scientific facts about these plants throughout this report.

A vast and diverse group

Along with daisies, orchids are part of one of the largest plant families known to science.

According to estimates released by Kew Gardens, more than 25 thousand different species of orchids have been described.

They grow on all continents, with the exception of Antarctica.

Their variety also draws attention. The smallest orchids in the world, such as Platystele jungermannioidesare just 3 millimeters tall.

The largest (Vanilla planifolia) has branches that reach up to 20 meters in length.

The tiger orchid, or Grammatophyllum speciosumhas flower stems up to 2 meters long.

Brazilian agronomist Marcelo Sellaro, who works at the Kew Gardens herbarium, explained that although around 70% of orchid species grow on trees, they are not considered parasites.

This is because they use the trunks and branches only as support and do not extract any sap from the tree. For this reason, they are described as epiphytic plants.

Another curious fact about orchids mentioned by Sellaro has to do with the relationship between these plants and the animals that carry out pollination.

Around 60% of the species in this family “deceive” small insects, which are attracted to the flowers — although the animals do not find any type of reward there, such as nectar.

Even so, when interacting with the orchid flower, the little animals come out of the petals carrying pollen, which is spread throughout the environment and allows these plants to reproduce.

Inspiration for Darwin

A noteworthy chapter in the relationship between humans and orchids involves Darwin, the creator of the Theory of Evolution.

In 1862 he received a sample of Angraecum sesquipedalea species from Madagascar that is popularly known as “star orchid” or “Darwin’s orchid” — for reasons that you will understand below.

This white and yellow flower has a striking characteristic: at the bottom, it has a very elongated tube, as you can see in the image below.

When analyzing the species, Darwin speculated that there must be an insect in the plant’s habitat with a proboscis (a type of tongue) so long that it reaches the end of the tube and sucks the nectar that accumulates there.

And this, in turn, would guarantee the spread of pollen from the Angraecum sesquipedale.

But there was a problem: at the time Darwin made this presumption, no animals with these characteristics had been observed in Madagascar.

Some experts even ridiculed the English naturalist’s hypothesis.

At the beginning of the 20th century, however, speculation about the “long-tongued insect” became reality: explorers identified the hawk moth, which in fact possesses the characteristics described by Darwin.

It received the scientific name of Xanthopan morganii praedicta —which in Latin means something like “the predicted moth”, in allusion to Darwin’s writings.

An article published on the website of the New York Botanical Garden, in the USA, recalls that the creator of the Theory of Evolution was an avid researcher of orchids and even wrote specific books about them.

And the Angraecum sesquipedale It ended up becoming a perfect example of coevolution, which occurs when two species — in this case, an orchid and a moth — interfere with each other’s growth and adaptation abilities.

A rare condiment

Another curious scientific fact related to orchids is the fact that vanilla is extracted from a plant that belongs to this family.

A Vanilla planifolia It has an elongated shape and grows similar to a vine.

It is a typical species of Mexico, Central America and the northern portion of South America, more specifically Colombia.

Vanilla is extracted from the pods that grow when the plant blooms. These fruits are dried and cured – Kew Gardens points out that the Aztecs were the first to use them as a condiment, in preparations that also included cocoa.

Nowadays, habitat changes have made Vanilla planifolia a species threatened with extinction — and much of its cultivation for consumption is concentrated in places where this orchid was introduced by humans, such as regions of Africa and Asia.

Also according to Kew, vanilla is the second most expensive condiment in the world, behind saffron.

The high value is due to the work required to cultivate the species. To give you an idea, outside of its places of origin this plant needs to be pollinated by hand.

The ‘canary in the mine’

In an interview with BBC News Brasil, botanical horticulturist Solène Dequiret describes orchids as the “canaries in the mine” of environmental conservation.

This term alludes to the practice of 19th century miners, who used to take canaries to coal mines.

The animal was used as a warning signal — if it died, there was strong evidence of the existence of toxic gases or a lack of oxygen in that environment, and the workers would run out of the mine, before meeting the same fate as the poor bird.

Returning to orchids, Dequiret highlights that they are very sensitive — and also signal a pressing danger.

“They are the first species to disappear [quando um ambiente começa a ser degradado]”, summarizes the expert, who is the supervisor of the Prince of Wales Conservatory at Kew Gardens, where the orchid festival was organized.

“In other words, they are a good indicator of the health of the environment in which they live.”

Kew Gardens estimates that about 50% of the world’s orchid species are at risk of extinction because of habitat destruction and climate change.