Thursday, 12 November 2015

How did the stonefly cross the lake? The mystery of stoneflies recolonizing a U.S. island

Date:  November 6, 2015
Source:  Pensoft Publishers

Massive glaciers once covered an island in one of the Great Lakes, USA, leaving it largely devoid of life. Its subsequent recolonisation by insects triggered the curiosity of entomologist R. Edward DeWalt and graduate student Eric J. South of the Illinois Natural History Survey and Department of Entomology. Not only did they prove there were significantly fewer species, compared to the mainland, but also that smaller stonefly species appeared to be more capable of recolonizing the island. This study was published in the open-access journal ZooKeys.

Isle Royale is a large island and national park in the middle of Lake Superior, isolated from the mainland by 22 -- 70 km distance. As recently as 8,000 -- 10,000 years ago, glaciers completely covered the island making it almost uninhabitable.

Over the last 10 millennia mammals as large as moose and wolves, swam, floated, flew, or walked on ice bridges to the island. Therefore, it seemed logical that it was the larger size that allowed some species to cross the water. However, as far as stoneflies are concerned, the results turned out quite different.


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