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When Avens bloom

Biologists investigate which insects pollinate one of the most widespread plants in the Arctic and gain new insight into the interactions between the organisms of the arctic food web.

In the laboratory of the Zackenberg Research Station in NE Greenland the scientists fabricate artificial flowers resembling the flowers of the arctic plant Avens. The flowers consist of sticky cardboard that catches the insects pollinating Avens. Photo: Peter Bondo Christensen.
With meticulous care Associate professor Tomas Roslin and biology student Mikko Tiusanen from Helsinki University, Finland, make 1,800 artificial flowers to catch insects at the tundra around the Zackenberg Research Station. Photo: Peter Bondo Christensen.
Artificial flowers among this year’s first blossoming Avens. Photo: Peter Bondo Christensen.
Mikko Tiusanen among real and artificial Avens flowers. Some of the flowers are protected by a small blue net that prevents insects from entering and pollinating the flowers. Photo: Peter Bondo Christensen.
Mikko Tiusanen at a so-called Malaise trap. The insects are caught by the wall of the tent and led to a container with alcohol. Photo: Peter Bondo Christensen.

The delicate white flowers of Avens rotate with the sun on the arctic tundra. The small pretty flower is one of the most widespread plants in the Arctic and constitutes an important food source for many plant eaters.

Even though it curtseys gracefully in the polar wind, it is an old lady. Avens may become as old as 100 years and is therefore of decisive significance for the terrestrial primary production.

For Avens to flower, grow and set seeds it must be pollinated, but so far the scientists have inadequate knowledge of precisely which insects visit the white flower in the light polar summer, thus ensuring the continuous existence of valleys and mountains with flowering Avens.

Associate professor Tomas Roslin and biology student Mikko Tiusanen from Helsinki University, Finland, will now seek to answer the question.

Sticky flowers

The two scientists plan to trick the Avens pollinators. Rather than settling in the sunny yellow centre of the flower and fill themselves with nectar, the pollinators will be lured into visiting an artificial flower – a sticky cardboard disc. The sticky cardboard is made of the same material used in greenhouses to remove unwanted insects.

When the insects have made the wrong choice and have settled on the artificial flower, there is no return. They will be glued to the cardboard disc, and Mikko will gather and determine each unlucky suitor to species level.

During the short summer season Tomas and Mikko will plant 1,800 artificial Avens flowers among the real flowers. The insects caught on the sticky cardboard will reveal the species pollinating Avens as well as the time of pollination during the short summer season.

By planting sticky flowers in different places, the scientists will gain knowledge of which insects occur where. And by measuring the seed production of Avens in the same places, they will be able to determine the importance of the different insects for the production of Avens.

Inclusion of the entire Arctic

The ongoing investigation is undertaken at the Zackenberg Reseach Station in NE Greenland. Even though the method applied is simple, it works well. On some summer days an artificial flower may catch up to five insects, and the scientists thus count on returning home with more than 10,000 insects later to be determined to species level.

Moreover, the two scientists have persuaded other researchers in the Arctic to use the same artificial flowers. Together, the samples will provide a unique data material elucidating whether small ‘creepy crawly’ creatures occur that will ensure the continued existence of an important plant in the Arctic of the future.

With the climate changes summer comes earlier and earlier to the high-Arctic area, influencing both insects and flowers. Highly likely, this will affect the continued presence of the various pollinating insects in the future; insects that need to carry on their important work to ensure the functioning of the entire ecosystem, and which decide whether the white flowers of Avens will continue to enliven the tundra in the future’s warmer climate.

The study of Avens and its pollinators is merely one of many sub-studies led by associate professor Tomas Roslin from Helsinki University, carried out at the Zackenberg Research Station in NE Greenland in collaboration with scientists from Aarhus University. The studies shed light on the functioning of the arctic foodweb and allow the scientists to predict the impacts of changes triggered by a warmer climate on plants and animals in the Arctic.

Further information:

Mikko Tiusanen, Department of Biosciences, University of Helsinki: Mikko Tiusane@Helsinki.fi

Tomas Roslin, Department of Agricultural Sciences, University of Helsinki: Tomas Roslin@Helsinki.fi

See also: http://www.helsinki.fi/foodwebs/Dryas/index.htm

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