The Leopard orchid and its interconnectedness with the world around it

Posted by Elly on Fri November 27, 2020 in Environment.

Very often, we consider the relationships that animals share with each other but do not credit plants for the important role they play in their broader ecosystem.

The Leopard orchid is a plant that shares numerous special relationships with other organisms in its environment, making it a wonderful example of the interconnectedness of the natural world.

As a favourite of our guides, and a flower that we are lucky to spot on our walking trails, we asked asked Elly to tell us a bit more about this ecologically fascinating flower.

In my opinion, the Leopard orchid (Ansellia africana) is one of the most interesting flowering plants out here in the Lowveld. Endemic to Africa, this gorgeous flower was named after British botanist John Ansell, who discovered the first specimens back in 1841 on an island called Fernando Po in West Africa. It is easy to see where its common name is derived as the yellow flowers are adorned with maroon spots, closely resembling those of the big cat.

What I find most incredible about the leopard orchid is the unique place it occupies in the ecosystem, the range of niches it fills and the number of relationships it shares with other organisms. The Leopard orchid is known as an epiphyte, which is a plant that grows on another plant. It does not parasitise its host plant, or steal nutrients for its own growth, but rather uses its host simply as an anchor or physical support. In nature, this type of relationship is known as commencalism, in which one organism benefits and the other is neither helped nor harmed.

The orchid's needle-like roots are specially adapted for gathering moisture quickly from the air and rain. Sometimes referred to as a "trash basket" orchid, this upward-growing, aerial root system creates a makeshift basket to catch falling leaf litter and detritus from the tree. This collection of organic matter is broken down by fungus which, in turn, releases nutrients for the orchid to feed on.

Interestingly, the mature flowers themselves do not produce nectar. Instead, nectar is exuded from the buds before they open and is used to recruit ants that forage on the orchid's flowers. In return for the sweet treat, these ants act as a first line of defence for the orchid, protecting it from hungry herbivores. This is known as mutualism, a relationship in which both organisms benefit from their association. To learn about other amazing, mutualistic relationships, you can read my recent blog article on the topic.

However, as a group of plants, orchids are well-known for their trickery and deception. In the case of the Leopard orchid, the sweet, citrusy scent produced by the flowers is what lures bees in to pollinate them, without the promise of a nectar reward. At night time, Hawk moths also come to feed on the sweetly-scented blooms.

Just like leopards, these orchids are often seen perched on the branches of large trees. But, how did they come to be there in the first place? The answer to this question is revealed when you look closely at the plant's seeds. 

The seeds of most plants contain a small nutrient package, which acts as a "kick-starter" for the seed once it finds a suitable location in which to germinate. However, this weighty addition is not ideal if your seeds are wind-dispersed, as is the case of the Leopard orchid. 

As a result, the nutrient package has been eliminated from the seed, making them light enough to travel on the breeze. Once the seed lands in the crevice of a nearby tree, it is unable to germinate until a certain fungus starts growing in the same area. In an almost criminal twist, the seed parasitises this fungus and hijacks it as a nutrient source to kickstart its own germination.

Perhaps even more fascinatingly, the Leopard orchid has a number of traditional and modern medicinal uses. The Zulu people have been known to use infusions of the stem and inhale smoke from the burning roots as an antidote to bad dreams. In Zimbabwe, it is also used as a protective charm and an aphrodisiac.

Recent scientific studies have highlighted the broad spectrum of medicinal properties that this plant actually has. The Leopard orchid has become an important source of various biomolecules that are used for the treatment of Alzheimer's disease, a brain disorder that results in severe memory loss.

However, due to its traditional and modern medicinal uses, this special plant is being indisriminately collected from the wild. This over-exploitation, coupled with large amounts of deforestation and habitat destruction, means the Leopard orchid has been categorised as “vulnerable” on IUCN Red List for plants.

It is clear just how special this plant is from the relationships it shares with trees, fungus and ants, among other organisms in its environment. While on walking safaris, we never miss an opportunity to point out the Leopard orchids to our guests as the perfect example of ecological interconnectedness and the importance of protecting plants, as well as animals, into the future.

 

Article written by Elly Gearing with photos courtesy of Matthew Plaistowe, Jess Bailey and Elly Gearing.