Surviving the ice: Northern refugia and postglacial colonization.

Area of Science:

• Ecology
• Evolutionary Biology
• Paleoclimatology

Background:

• Organismal responses to Earth's geological and climatic history are crucial for understanding current biodiversity.
• Quaternary glacial cycles significantly influenced north-temperate biodiversity, with ice sheet expansions and contractions shaping species distributions.
• Prevailing theory suggests temperate organisms shifted ranges southward to refugia during glacial periods and recolonized northward as ice receded.

Purpose of the Study:

• To investigate the impact of glacial cycles on the distribution of biological diversity in the central U.S.
• To examine the population genetics and historical distribution of the eastern chipmunk (Tamias striatus) in response to past climate change.
• To challenge the assumption that all temperate species migrated south during glacial maxima.

Main Methods:

• Analysis of fossil and palynological data to reconstruct past environments.
• Genetic analysis of eastern chipmunk populations to infer historical movements and refugia.
• Comparison of genetic data with paleoclimatic models.

Main Results:

• Evidence supports the existence of a large southeastern glacial refuge for temperate organisms.
• Data from the eastern chipmunk reveals the maintenance of multiple refugial sources.
• The study identified a southward expansion from a northern refugium for eastern chipmunks, contradicting simple southern migration models.

Conclusions:

• Organismal range shifts during glacial periods are more complex than previously assumed.
• The eastern chipmunk's distribution suggests that not all temperate species necessarily migrated south to track favorable climates.
• Multiple refugia and varied migration strategies likely contributed to the current distribution of temperate biodiversity.