PaleoEcoGen - Understanding past ecological trends

Changes in ecosystem dynamics can occur gradually over centuries to millennia, or may be very abrupt (i.e. over a few years), which challenges the fitness and survival of many organisms. Rapid ecosystem changes can be triggered by small disturbances that may weaken the system - with or without visible signs - but ultimately lead to the crossing of a critical point, when “critical transitions” occur (i.e. where the system is pushed from one equilibrium state to another; Taranu et al. 2018). These ecological transitions are often hard to predict because of the complexity of the interactions between organisms and their environment. Furthermore, critical transitions are difficult to reverse and thus, they can have prolonged consequences.

Critical transitions have been documented for terrestrial and aquatic (lacustrine, marine) ecosystems, as well as social-ecological systems, and have been studied in climate and social economic sciences as well as in archeology (Scheffer et al. 2009, 2012). In the context of global changes, especially the "Great Acceleration" (Steffen et al. 2015), studying critical transitions is timely, and has been identified as a priority paleoecological research area (Seddon et al. 2014). With new methodological approaches on the rise in the paleo-sciences there now is a good opportunity to describe past critical transitions and study the mechanisms behind (Taranu et al. 2018).

With this background, our working group is motivated to address the key question: what can we learn about the mechanisms leading to critical transitions and their subsequent evolutionary and ecological trajectories based on the comparison of biomes in paleo-records from terrestrial and aquatic biomes?

The detailed study of critical transitions in paleoecology requires the generation of the most comprehensive view possible - of an ecosystem and its drivers. To meet this challenge, ancient environmental DNA (ancient eDNA, which includes sediment DNA) is a key tool because of its potential to provide new insights into:

1. the composition of biological communities across multiple trophic levels;
2. species interactions within communities;
3. how organisms, from populations to whole communities, have responded to environmental changes in the past (Domaizon et al. 2017).

Like any proxies, ancient eDNA has its limitations, but it also offers new and extremely valuable information that is expanding knowledge from existing paleo-approaches. For instance, it has contributed to advance our understanding of ecosystem trajectories and their drivers, notably under growing pressures of human societies at a global scale (Parducci et al. 2017; Armbrecht et al. 2020; Capo et al. 2021).

Ancient eDNA can be used to study the past distribution of most organisms from all domains of life, including those that are not identifiable or distinguishable under microscope, i.e. species that do not leave skeletal remains in the sediment archive and cryptic species, respectively. Because ancient eDNA can be applied simultaneously to multiple taxonomic groups, this approach has the potential to detect ecosystem-wide changes, which help define more precisely the timing of shifts in biotic interactions like food webs. This may contribute to identifying early indicators of change (i.e. early warning signals), which would be highly relevant for ecosystem management. Finally, ancient eDNA proxies can be used in multivariate analyses, such as network analyses aimed at estimating complex relationship patterns across a set of biotic and abiotic variables. We will work on developing a multivariate dynamic linear model approach (based on past and current work of Taranu and Carpenter) to investigate the timing and magnitude of shifts in sediment records in various paleo-environments based on ancient eDNA data.

Background

PaleoEcoGen will complement the work of the previous working group (WG) Aquatic Transitions (2014 to 2018), which contributed to advancing our understanding of the impacts of past human-driven disturbance on lake ecosystems. PaleoEcoGen will conduct an in-depth exploration of the potential of ancient eDNA in defining the dynamics and magnitude of ecosystem responses to both natural and anthropogenic forcing.

Our WG will initiate discussions with former members of Aquatic Transitions, the current Human Traces WG, and other collaborators to continue developing a multivariate analytical framework for critical transitions that will include ancient eDNA as paleo-proxy.

Moreover, we will interact with the other current paleo-proxy focussed WGs (C-SIDE, ACME, LandCover6k) to investigate the biological signals archived in paleoenvironments.

Planned activities

This first phase of the WG will last three years (2021–2024). Due to the current COVID-19 pandemic situation and ongoing travel restrictions, we will not plan in-person activities before the first quarter of 2022. Until then, the Steering Committee plans to hold:

1. bi-monthly meetings to set up and coordinate WG activities on manuscripts/funding applications (mid 2021–2024);
2. monthly online seminars and panel discussions on various topics related to the use of ancient eDNA to answer ecological questions related to critical transitions;
3. a virtual thematic workshop (end of 2021) to discuss the existing records/data that is available and the theory to develop a framework for detecting and qualifying critical transitions in different environments using ancient eDNA data (working with a modified multivariate version of the Taranu et al. 2018 analytical framework);
4. A hybrid virtual/in person workshop focused on applying the models developed in 3) for a final synthesis paper.

The first in-person workshop is planned at the PAGES OSM in Agadir, Morocco in May 2022 (also open to online participants). This workshop will be dedicated to the training of African researchers to the use of eDNA methods with a specific focus on ancient eDNA approaches. This workshop will be co-organized with the African sedaDNA working group, also initiated by members of the sedaDNA scientific society.

The second meeting (hybrid in-person/virtual) is planned to be held in 2022 at the ESA meeting (14-19 August) in Montreal, Canada. This meeting will focus on applying the models developed previously (discussed end of 2021) to detect critical transitions using existing ancient eDNA time-series. This work will lead to a synthesis paper.

A third meeting (TBD) would focus on producing a perspective paper (2023–2024) to design methodological studies and inter-lab work (field and laboratory work, bioinformatics and data analysis workflows) in order to fill identified knowledge gaps related to methodology and best practices in ancient eDNA research.

Learn more and participate

This group is open to anyone who is interested, and early-career researchers are encouraged to be involved.

> Find out more about the group's scientific goals

> Contact a member of the Steering Committee

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