The ghost of ice ages past: Impact of Last Glacial Maximum landscapes on modern biodiversity

Modeled modern and Last Glacial Maximum (LGM) climate ranges for 47 genetically confirmed small Holarctic land snails documented profound landscape dynamism over the last 21,000 years. Following deglaciation, range areas tended to increase by 50% while isolating barrier widths were cut in half. At the same time, the nature of isolating barriers underwent profound change, with the North American continental ice sheet becoming as important in the LGM as the Atlantic Ocean is today in separating Nearctic and Palearctic faunas. Because appropriate modern climate occurs for these species throughout the Holarctic, with no clear barriers being present—especially for such efficient passive dispersers—the current >90% turnover observed between Eurasian and North American species pools appears at least in part related to the LGM landscape. Understanding current and predicting potential future biodiversity patterns thus requires consideration of the landscape template across at least 15,000 years time scales.