"For all except one species, multiple seeds were necessary to bring the observed genetic diversity to Svalbard," says biologist Inger Greve Alsos of The University Centre in Svalbard. "For mountain avens, we estimated the number of seeds that arrived in Svalbard to be 1,560 to 132,000."
The team of European researchers used so-called DNA fingerprinting—examining genetic differences in a specific fragment of the plant's genome—to trace these plants back to their roots. Surprisingly, the most common source of new plants appears to have been a land mass hundreds of miles away: northwestern Russia.
"We do not know exactly how these plants are dispersed as this never has been observed directly," Alsos says. But Russia is often connected to Svalbard by continuous sea ice and the predominant southeasterly winds blow from there toward these islands. "We think that the ice may have been important for dispersal of plants, either by transporting them directly or by acting as a bridge on which the wind may blow seeds across."
Svalbard has also been repeatedly colonized by plants from Greenland, Iceland and even Canada, though not often by those from Scandinavia, its nearest neighbor to the south that includes mainland Norway. "Recurrent glacial cycles have probably selected for a highly mobile arctic flora," the researchers report in Science. "In addition, some dispersal vectors may be particularly efficient in the Arctic as a result of the open landscape."
This is good news for Arctic plants as they will likely have to move again soon thanks to climate change. The mountain avens and the highland saxifrage will follow the retreat of the island's glaciers, though they may eventually run out of room if the poles warm too much or Arctic ice disappears entirely. And new species will likely cross to Svalbard from surrounding regions, mainly shrubs. "Colonization by shrubs, for example willows, would have a cascade effect on the ecosystems in Svalbard as there are only very fragmented populations of shrubs [there] today," Alsos says.
But this mobility of Arctic plants has limited applicability to greenery that thrives in lower latitudes, Alsos adds. Narrow species ranges and fragmented appropriate habitats (as well as man-made and natural barriers like cities and mountains) will make it hard for more temperate and tropical plants to move. Hence, the Svalbard Global Seed Vault that the Norwegian government is building deep in the permafrost as a last refuge for millions of seeds in case of global catastrophe—natural or man-made. The icy archipelago may prove to be a last resting place for many species beyond its native Arctic flora.