The endangered Saimaa ringed seal is an Ice Age relict living in the highly labyrinthine Lake Saimaa, Finland. The newly published work shows that although individual seals have greatly reduced genetic variation, the loss of variation has been complementary, preserving the adaptive potential of the whole population.

 

Lake Saimaa, a highly labyrinthine lake in eastern Finland, provides a unique opportunity for assessing the effects of population fragmentation. The lake hosts a population of ringed seals (Pusa hispida saimensis) that became landlocked as the land rebounded after the retreat of the continental ice sheet 10,000 years ago. Today, the Saimaa ringed seal, with some 400 individuals, is one of the world's most endangered seals.