Understanding climate refugia and quaternary biome development: From palynology to paleomics

Background/Question/Methods

“Paleoecology, once regarded as a quaint but irrelevant specialty, is on the verge of joining mainstream ecology …” (M.B. Davis, 1994).  Davis has played a key role in shaping Quaternary paleoecology into a rigorous and widely accepted branch of ecology and in training a generation of leading paleoecologists.  Over the past decades, paleoecology has evolved from its focus on pollen-based vegetation reconstruction to a rich research enterprise that embraces a diverse array of approaches to address the “totality” of past environmental change (paleomics).  Paleoecological analyses are now indispensable for testing ecological theories, validating earth system models, and elucidating the patterns and tempos of ecological dynamics in response to climatic change.  This presentation will discuss recent advances in understanding climatic refugia by integrating paleoecology, phylogeography, and species distribution modeling.

Results/Conclusions

Climatic fluctuations occurred throughout the geologic history, and many organisms have undergone dramatic abundance and range shifts.  Paleorecords, genetic surveys, and the modeling of species distributions each provide relevant insights into the complex histories of populations and species.  The emerging body of evidence regarding historical climate refugia expands our knowledge on ecological resilience, improves estimates of species migration rates in response to shifting climates, and contributes to explain spatial patterns of biodiversity on the modern landscape.  Evidence is compelling that many temperate and boreal species maintained small populations at higher latitudes than previously thought during the last glaciation.  Postglacial range expansions from these refugia often occurred in various directions, and lineages departing from different refugia may have converged and mixed extensively to result in higher intra-population genetic diversity than in areas farther south.  The survival of small populations in climate refugia provides a way to reconcile the “Quaternary conundrum” –- that extinction rates were low in paleorecords despite dramatic climatic shifts.  Recent studies also revealed spatial congruency of past climatic refugia and today’s species diversity hotspots, implying that climate refugia have played a crucial role for the long-term maintenance of biodiversity and that refugia may similarly serve as ‘safe havens’ under future climate warming.  Ongoing advances include applying genomic techniques to phylogeographic surveys, combining networks of climate sensors with regional climate simulations to elucidate the role of complex terrain in maintaining species, and developing a quantitative framework for rigorous assessment of past refugia and migration patterns. These advances promise to greatly enhance our understanding of population dynamics under changing climatic conditions.