Nature Blog Network

Thursday, July 19, 2007

You Can Always Trust an Amphipod to Survive the Ice Age

Photo credit: Crymostygius thingvallensis; Kristjánsson and Svavarsson 2004

Amphipods are truely amazing creatures. I've posted on them before and you can expect a plethora of posts in the future. Especially since I am trying to ID some right now from my quantitative community collections from the Lau Basin hydrothermal vents. So they are fresh in my mind.

I was very surprised today when I discovered that the ScienceDaily headline, Ice Age Survivors Found in Iceland, was not about neanderthals but amphipods! This news release highlights the research of Kristjánsson and Svavarsson in the endemic amphipods of Iceland's groundwater, recently published in American Naturalist. This study is fascinating for the reason that the island of Iceland has a known geologic beginning, around 30 million years ago, and known glacial period starting around 2.6 million years ago and ending 10,000-12,000 years ago. Most scientists believe that the glacial periods wiped out most of the terrestrial and freshwater fauna, except that may have found refugia near the edges of the glaciers. The author's discovery of 2 new species of groundwater amphipods
"strongly suggests that during the glaciations there was a subglacial refugium in Iceland where the amphipods could apparently survive in groundwater flowing through the porous lava bedrock that was constantly built up by active volcanoes throughout the glacial and interglacial periods."-Kristjánsson and Svavarsson 2007
They cite three key pieces of evidence:
1) biogeographical patterns of the groundwater amphipods across the northern hemisphere
2) the new amphipods are the only freshwater ones in iceland with the new species pictured above being the representative of a new family, the Crymostygiidae, signaling the antiquity of amphipod in question
3) limited dispersal capability of subterranean amphipods, hence little colonization potential. They easily rule out dispersal via migrating birds since the closest place with closely related species is in southern England and Ireland.

Though they can't say exactly when and where a subglacial refugia formed, they offer this interesting point, where biology may aid in understanding geology:
"The presence of the Icelandic subterranean freshwater species belonging to an old group with a current distribution mainly in North America and the Eurasian continent indicates that the subterranean freshwaters of Iceland were in contact with continental groundwater at some time."-Kristjánsson and Svavarsson 2007
This is yet another reason why amphipods are cool. Their subterranean relatives' patchy distribution, ability to survive harsh conditions, low dispersal capability, and the ability to adapt on a short time scale makes them model organisms to understand the evolutionary ecology of isolation by geological and ecological factors. I hope the next step that these authors take is to examine the population genetics and phylogeography of their new icelandic amphipods and compare them to counter parts in eastern US and western Europe. Perhaps this will bring to light the origin of their beasties.

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