Climate change and faunal dynamics in the uttermost part of the earth

To use the 'lessons of the Pleistocene' to forecast the biotic effects of climate change, we must parse the effects of history and ecology in the Quaternary record. The preponderance of Northern Hemisphere studies of biotic responses to climate change provides a limited set of players and environmental circumstances with which to decouple these drivers. In this issue Lessa et al. (2010) examine population structure in 14 species of mice distributed across Patagonia and Tierra del Fuego in southern South America. In the Southern Cone, glacial ice was alpine, not polar; major habitats were (and are) oriented N-S, not E-W; and habitable land area actually increased, not decreased, at the height of the last glacial maximum (LGM). Despite these differences, there is evidence for poleward demographic expansion in 10 of the 14 species, and phylogeographic breaks in these are likewise stepped by latitude (and presumably history) rather than by biome. Nevertheless, high latitude endemism and the antiquity of these lineages point to an extended presence in the region that very likely predates the Pleistocene.