Eideard

Mediterranean wasp spiders spreading to northern Europe

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Temperature tolerance is key to the spread of wasp spiders into northern Europe, according to scientists.

Since the 1930s the distinctive spiders have expanded their range from the Mediterranean coast to Norway…Researchers in Germany traced the population boom to breeding between the native European spiders and an isolated colony living near the Black Sea.

Molecular Ecology reports the genetic mixing resulted in generations rapidly adapting to living in colder climates.

Wasp spiders (Argiope bruennichi) are commonly named for their bright, striped abdomens and were recently recorded by the Woodland Trust in Usk, south Wales for the first time.

The first official records of this conspicuous species in the UK were made in the 1920s.

Henrik Krehenwinkel from the Max Planck Institute for Evolutionary Biology, Germany, analysed the DNA of spiders caught across their current range, and museum specimens to understand more about their evolutionary history.

Piecing together the genetic puzzle, he found that the spiders diverged after the last ice age: part of the population stayed on the Mediterranean while a colony headed east to Central Asia.

While these eastern populations adapted to live in climates as diverse as the tropical south of Japan and cold south-eastern Siberia, the spiders in the Mediterranean remained limited to warm areas.

But, according to the research, rising temperatures across the continent in the last century allowed the Mediterranean spiders to join up and breed with a previously isolated Black Sea population

Balloon spiders

He theorised that the novel combination of genes resulted in new physical characteristics that helped spiders to survive in different environments.

Mr Krehenwinkel described the hatchlings as “highly dispersive”, commenting that they can cover huge distances via a method known as “ballooning”: riding the breeze on a special parachute made of gossamer silk threads.

“By aerial dispersal, little spiders can cover distances of several hundred kilometres,” he told BBC Nature.

Cripes. One of my favorite signs of spring really making it to our tough dry terrain and altitude is the silk from balloon spiders being captured by our East-facing fence. Generally blown there by a warming West wind.

I wonder if our balloon spiders are distant kin of the wasp spider?

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