New DNA approaches to understanding Late-Quaternary and recent biodiversity changes – potential and problems

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• Prof Mary E. Edwards, Department of Geography and Environment, University of Southampton (UK)
• Thursday 19 February 2015, 17:30-18:30
• Thirkill Room, Clare College.

If you have a question about this talk, please contact Julia Gottschalk.

Major advances in the ability to sequence many DNA samples has led to a proliferation of Quaternary molecular studies. The Ecochange project developed a methodology that allows DNA of vascular plants and mammals to be extracted from Quaternary sediments and used as proxy data for the components of terrestrial ecosystems. It uses an approach called “metabarcoding”: for plants, this is based on short (10-200 BP) sequences of chloroplast or nuclear DNA . Taxonomic resolution is potentially better than that of pollen and matches that of macrofossils. Furthermore, DNA detects the presence of taxa at when biomass levels are relatively low. I will illustrate the current status of DNA -based palaeoecological reconstructions with a range of modern (calibration) and fossil studies from Siberian yedoma, northern lake sediments (from Svalbard and Scotland) and modern tundra landscapes. Key findings are that modern soil DNA matches the taxa present in modern vegetation with few false positives and roughly reflects biomass, that DNA in lakes does not seem to reflect pollen when there is no vegetative biomass in the catchment, that forb taxa were a surprisingly large component of glacial-age vegetation across unglaciated Eurasia, and that the Holocene DNA record from Svalbard shows rapid early colonization and resilience of the flora in the face of climatic deterioration. New and stricter protocols for sequencing and bioinformatics filtering are improving the ability to determine false positives in the data, which were likely a problem in the first, pioneering studies.

This talk is part of the Quaternary Discussion Group (QDG) series.

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