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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - AMBER (Dating fossils with molecules â€“ innovative approach to determine the age of Baltic AMBER)

Teaser

Summary

Baltic amber from Northern Europe is an outstanding deposit due to the high diversity of well-preserved inclusions, mostly insects. Although it is one of the richest sources of fossils, science has consistently failed to define its geological age, despite applying various traditional approaches. There are several hypotheses concerning the age of Baltic amber, which is generally dated as Eocene, with an age range between 55 and 34 Ma. Difficulties in the age determination are essentially due to the repeated re-deposition of the amber, the broad range of the ancient forest and its probable existence for several million years. It limits the scientific value of all Baltic amber fossils in evolutionary divergence time estimation. This is very unfortunate, especially because these fossils would be very important for reconstructing evolutionary events in the Eocene, which was a period of dynamic climate, with several warming and cooling events and is considered as a deep-time analogue of current climatic changes.

The core idea of my project is to apply an innovative approach of precise dating for this very important fossil deposit by using DNA, morphology of extinct and extant species within the framework of advanced Bayesian statistics. Information contained in DNA sequences together with the morphology of both extinct and extant taxa will allow for estimating phylogenetically the age of fossils from Baltic amber, and thus the amber itself. I am using a dataset from my previous project as a basis, and expand it with fossils from Cenozoic deposits worldwide.

Firmly established age of the Baltic amber fossils will be a breakthrough for evolutionary biology, palaeoecology, biogeography, and palaeoclimatology. It could give us an insight on the ecosystems\' response to the dynamic climate changes that took place in the Eocene and shaped out the recent biota.

Work performed

I began the outgoing phase of the project from collecting additional morphological data on fossils belonging to my study group, rove beetle subfamily Paederinae (Staphylinidae), from Cenozoic deposits. I visited several most important fossil collections in the USA, which gave me an overview of the Paederinae fossil material from the most diverse terrestrial Cenozoic deposits. Based on that knowledge, I chose several fossils and scored them into morphological dataset. At the same time, I was collecting information on first and last occurrences of the fossil taxa and the age of fossil deposits other than Baltic amber.

After gathering all this information, I ran a phylogenetic analysis of the morphological and molecular data with simultaneous divergence time estimation on the smaller subset of my dataset. I used fossils from non-Baltic amber deposits to phylogenetically estimate the age of Baltic amber fossils. For each Baltic amber fossil, I performed a separate Bayesian phylogenetic analysis in which the fossilâ€™s stratigraphic data were replaced by the prior, and thus I obtained a phylogenetic estimate of the fossilâ€™s age. All analyses were done in RevBayes, which is statistical software package using probabilistic graphical models for estimating evolutionary parameters in a phylogenetic context and providing a flexible environment for fully integrative Bayesian analysis.

As the last step, together with my supervisor and designated postdoc, we validated the method performance and reliability by running a series of designed simulations. Simulated datasets are extremely useful tools because they can characterize the expected performance of phylogenetic methods under idealized conditions to test and validate newly implemented methods. The simulation study was run to assess whether well-dated fossil samples can be used in combination with extant samples, to date fossil samples from a deposit of unknown age.

The main results obtained so far are the phylogeny of the rove beetle subfamily Paederinae and the first dates for Baltic amber deposits.

Final results

The preliminary results of the project significantly expand our knowledge on the Paederinae rove beetle systematics and evolution. My research shows that they are one of the oldest rove beetle subfamilies, but the main speciation events leading to the current diversity took place in Cenozoic, specifically in Eocene. My studies indicate that they were important elements in different terrestrial Eocene ecosystems, which could help us to understand the patterns and processes leading to their recent diversity and distribution. As Paederinae rove beetles are having potential in biomedical, pest management and conservation research, expanding knowledge on their systematics and evolution have wider societal implications. The first results of using a phylogenetic approach to date Baltic amber are highly promising and already show the potential of applying this method to difficult fossil deposits.

Knowing the age of Baltic amber is important for reconstructing evolutionary events in the Eocene, which was a time of drastic climatic changes analogues to the current global warming. Climate change is among the most important environmental issues in the recent world, and its impact on biodiversity and ecosystems is not only of scientific interest but also stands high in scientific and political agenda of the modern world. Well-dated Baltic amber could be used as a tool for reconstruction of the climate and environment in the Eocene in Europe. It could help us to understand the current geographic distribution of different groups and their species composition, which in turn, could indicate how the past ecosystem was reacting to these events and recovering after global warming.