Wednesday, January 13, 2010

Newly-Discovered Species of Cricket Pollinates Orchids

Photo courtesy: RBG Kew/Michenau and Fournel

Reunion Island is a French island located in the Indian Ocean east of Madagascar, about 200 km (120 mi) south west of Mauritius, the nearest island.

Claire Micheneau is a Royal Botanic Gardens, Kew-associated PhD student studying how the epiphytic orchid genus Angraecum has adapted to different pollinators on Reunion Island.

While researching orchids on the island, Claire Micheneau noticed that the flowers were being pollinated from an unknown source. Since she was unable to find the culprit during the day, she set up motion-activated cameras and surveilled the flowers at night.

What she discovered was a previously-unknown species of pollinator that was acting in a manner quite contrary to the behaviour of its known relatives. So, what is pollinating the orchids of Reunion Island?

Claire Micheneau had discovered a species of cricket previously unknown to science.

The flowers of the Angraecum genus of orchids. Photo courtesy: RBG Kew

Micheneau was on Reunion studying the Angraecum genus of orchids. This group of flowers became well known for the research Charles Darwin conducted on them in Madagascar. The comet orchid (Angraecum sesquipedale) has a very deep nectar cup that is relatively inaccessible to many pollinators. Darwin hypothesized that they could possibly be pollinated by moths with really long tongues. Many years after his death, Darwin was proved to be correct.

On Reunion, however, pollination had remained a mystery because none of the usual agents are present. Micheneau explained that:
We knew from monitoring pollen content in the flowers that pollination was taking place. However, we did not observe it during the day...the moths that are the main Angraecum pollinators on Madagascar are not found on Reunion and until we started our research the pollination of this genus on Reunion had always been an open question.

Micheneau described the feeling of finding that a cricket to be at least partially responsible for pollinating the orchid as “thrilling”. It demonstrates, she explained, a "truly surprising shift in the pollination of Angraecum."

A "raspy cricket" carrying orchid pollen on its head. Photo courtesy: RBG Kew/Michenau and Fournel

The idea that a cricket could be a pollinator was something that had never been considered before because crickets are generally omnivores. Usually, crickets of the Orthoptera order eat plants and other insects.

Micheneau believes that the crickets eat nectar instead of the plants themselves because of the unique environmental conditions on the island. She says, “we think the raspy cricket has evolved to eat nectar to compensate for the general scarcity of other insects on Reunion."

While her research showed that two species of songbirds have also evolved as orchid pollinators, the raspy cricket has proven to be much more effective at the job. Orchids populated by crickets showed higher rates of pollination and fruit set than those frequented by the bird species.

Via TreeHugger

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