Iceland has its first and second endemic animal species on record and they’re both amphipods – little crustaceans that are sort of like krill … in the same way that krill are sort of like shrimp. (Readers who know their small marine critters are invited to chip in with details.)
What’s neat about them is that they live underground, sipping the sweet, fresh water that gurgles through the lava rock. And one of them belongs to a very old family of underground amphipods found in both North America and Europe.
Many people, upon learning such a fact, would go “Neato” and click onward. But Bjarni Kristjansson and Jorundur Svavarsson of Holar University College realized this meant that Iceland probably shared groundwater with one of those continents a long time ago. They argue (in American Naturalist) that it was most likely Greenland, and most likely about 40 million years ago, after the Atlantic Ocean had ripped open and just as the hotspot that created Iceland passed through the coast of Greenland.
For much of the time since then, the amphipods have been hiding out from repeated glaciations in relatively warm, safe groundwater. The typical way we think species survive glaciations is to move southward until the glaciers retreat, then hopscotch back to the north. Not an option on Iceland.
Instead, the authors think the amphipods sat underground and waited out each glaciation. The last one iced over Iceland from 2.6 million years ago all the way to about 12,000 years ago. That’s one reason why there are so few endemic species on the island – nobody’s been there long enough yet to speciate.
The authors make a pretty good argument. The amphipods are from a freshwater lineage, so they couldn’t have swum over through the sea. If they came from nearby amphipods who evolved to tolerate freshwater, then they would belong to a different family. And it’s unlikely they hitched a ride on birds’ feet (as tadpoles sometimes do) because their eggs are delicate.
This is why I love science. The stories start small, then they interlock and get bigger. One moment we have a water-flea (well, not taxonomically, but you know what I mean). An underground water-flea. Buried under miles of ice. In the middle of the ocean. Swimming through a secret underground connection. As Iceland flames out of Greenland and into the North Atlantic. Back during the dawn of mammals.
Image: Holar University College. My apologies for the missing umlauts, accents, etc. in the authors’ names.