The maturing relationship between Quaternary paleoecology and ancient sedimentary DNA

In the two decades or so since ancient sedimentary DNA (sedaDNA) took its place as a new Quaternary paleo-proxy, there have been large advances in the scope of its applications and its reliability. The two main approaches, metabarcoding and shotgun sequencing, have contributed exciting insights into areas such as floristic diversity change, plant-herbivore interactions, extinction, conservation baselines and impacts of invasive species. Early doubts as to its potential to contribute novel information have been dispelled; more is now understood about the passage of sedaDNA from the original organism to a component of soil or sediment and about the range of uncertainties that must be addressed in the interpretation of data. With its move into the mainstream, it is now time to develop effective data archives for sedaDNA, refine our understanding of central issues such as taphonomy, and further expand the potential for describing, both qualitatively and quantitatively, the history of past ecosystems.

Community ecology in a changing environment: Perspectives from the Quaternary

Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a “missing middle”: Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit.

Radiocarbon Dating of Individual Amino Acids from Archaeological Bone Collagen

Since the development of accelerator mass spectrometry (AMS) for radiocarbon dating in the late 1970s, its ability to date small samples of bone has been of huge importance in archaeology and Quaternary paleoecology. The conventional approach to sample preparation has been to extract and gelatinize protein, which is then combusted and graphitized for analysis. However, this “bulk protein” can contain a heterogeneous mixture of non-collagenous molecules, including humic acids and other soil components that may be of a different age than the bone and therefore affect the accuracy of its 14C date. Sample pretreatment methods have been an important area of development in recent years but still show inadequacies for the dating of severely contaminated bone. The idea of isolating and dating individual compounds such as single amino acids, to improve dating accuracy, has been discussed in the literature since the 1960s. Hydroxyproline, for example, makes up over 10% of bone collagen but is extremely rare in most other animal proteins, increasing the chances of its presence being endogenous to the individual being dated. Its successful isolation has therefore been considered a potential “gold standard” for dating archaeological bone; however, extracting and suitably purifying single amino acids from bone has proved a challenging task.