Evidence for cryptic northern refugia among high- and temperate-latitude species in Beringia

Stewart and Dalén (2008) argue that only temperate species were locked in cryptic northern refugia during Pleistocene glacial cycles, while species presently found at high latitudes had much wider distributions during glaciations. We present evidence supporting the existence of cryptic northern refugia that likely harbored both high- and temperate-latitude species in the Bering Sea region. Genetic signals of refugial isolation are found in island populations of rock ptarmigan (Lagopus muta), rock sandpiper (Calidris ptilocnemis), common raven (Corvus corax), and winter wren (Troglodytes troglodytes). These species have high-latitude, a mixture of high- and temperate-latitude, and temperate-latitude distributions. In addition, there are no data showing historically larger distributions of the high-latitude rock sandpiper or rock ptarmigan in North America during the Pleistocene. Although exact dating of isolation events is not possible using molecular genetic data, the species we examined have similar genetic signals and thus were isolated at similar times. It is evident that Pleistocene glaciations produced refugial genetic signatures among multiple bird species in the North Pacific Ocean.