Rare orchids mimic fungus to attract flies

Apr 27, 2011 by Deborah Braconnier report
Cypripedium fargesii
Cypripedium fargesii Image credit: srgc.org.uk

(PhysOrg.com) -- In a recent study published in the Proceedings of the National Academy of Sciences, Zong-Xin Ren from the Chinese Academy of Sciences and Peter Bernhardt from Saint Louis University discuss the lady’s slipper orchid (Cypripedium fargesii) and its ability to mimic the Cladosporium fungus in order to attract the flat-footed fly for pollination.

This particular is an extremely rare and endangered flower that is found only in the southwestern mountains of China. Ren spent four summers climbing Yaoshan Mountain at 3,000 meters above sea level where a hundred or so of these flowers are found.

When it comes to general flower pollination, the flowers usually offer something to the insects in order to attract them, be it food, water, or specific chemicals. However, the lady’s slipper orchid has nothing to offer potential visiting insects.

While most flowers are usually pollinated by bees, Ren found the only insect to visit these orchids were the flat-footed fly. The flat-footed fly feeds on and, like the orchid, is extremely rare.

In order to attract the fly, the orchid mimics this fungus with the spots on its leaves and the odor it releases. The scent, similar to the smell of the fungus the flat-footed flies feed on, attracts the flies and the spotted leaves visually make it look as though it is infected with the particular fungus.

When the fly enters the flower, it has to follow a specific path to get out, passing the pollinators which deposit clumps of pollen onto to the fly who then carries it to the next flower he visits. Ren also discovered that the flowers go one step further in that the center of the flowers are hairs (trichomes) that have evolved to look like the fungal spores.

When the team analyzed the flies, they found fungal spores on the mouth, head, feet and pads, as well as the pollen from the on their backs. Ren is planning further research to discover why the fungus carried by the flies does not infect the orchid. He also wants to know if the relationship between the and the orchid play any contributing factor to them both holding a rare status.

Explore further: Study shows exception to rule of lifespan for fliers, burrowers and tree dwellers

More information: Flowers of Cypripedium fargesii (Orchidaceae) fool flat-footed flies (Platypezidae) by faking fungus-infected foliage, PNAS, Published online before print April 18, 2011, doi: 10.1073/pnas.1103384108

Abstract
Charles Darwin was fascinated by the orchid–pollinator interactions, but he did not realize that many orchid species are pollinated by deceit. Cypripedium, a model lineage of nonrewarding orchid flowers, is pollinated primarily by bees. Here we present both an example of floral mimesis of fungus-infected foliage in orchids and an example of flat-footed flies (Agathomyia sp.; Platypezidae) as pollen vectors for angiosperms. Cypripedium fargesii is a nectarless, terrestrial, endangered orchid from southwestern China that requires cross-pollination to produce the maximum number of viable embryos. All insects caught entering or leaving the labellum sac were Agathomyia sp. carrying conidia of Cladosporium sp. on their mouthparts and legs, suggesting mycophagy. Blackish hairy spots on the upper surface of foliage may imitate black mold spots, serving as short-term visual lures. Some odor molecules also associated with Cladosporium cultures were isolated in the floral scent. Mimesis of fungus-infected foliage probably represents an overlooked but important option in angiosperm diversification, because there are three to five more Cypripedium spp. in southwestern China with the same mode of floral presentation and black-spotted hairy leaves.

Related Stories

Orchid wears the scent of death

Mar 14, 2011

Sex and violence, or at least death, are the key to reproduction for the orchid Satyrium pumilum. Research led by Timotheüs van der Niet at the University of KwaZulu-Natal shows that the orchid lures ...

New research explains orchids' sexual trickery

Dec 17, 2009

A new study reveals the reason why orchids use sexual trickery to lure insect pollinators. The study, published in the January issue of The American Naturalist, finds that sexual deception in orchids leads to a more effici ...

Orchid sexual deceit has male wasps in a loved-up frenzy

Apr 29, 2008

Orchids are admired by humans and insects alike, but according to Macquarie University research, one Australian wasp is so enthralled by ‘Orchid Fever' that actually he ejaculates while pollinating orchid ...

The cost of long tongues

Apr 16, 2007

Orchid bees use their extraordinarily long tongues to drink nectar from the deep, tropical flowers only they can access. Researchers have long suspected that this kind of exclusive access came with a mechanical ...

First radio tracking of tropical orchid bees

May 26, 2010

Blue-green orchid bees zip through increasingly scarce patches of tropical forest pollinating rare flowers. For the first time, researchers at the Smithsonian Tropical Research Institute track unique signals ...

Recommended for you

Orchid named after UC Riverside researcher

1 hour ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

3 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

3 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Orchid named after UC Riverside researcher

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...