By: Nathan Martin
The emergence of the agro-pastoral way of life transformed the ecosystems and the dynamics of the biodiversity. This transition took place in a period of important climate variability, marked by different climatic events, which have influenced its spread and the local biodiversity. Nevertheless, differentiate which part of the fauna and flora variability results from the anthropic or climatic impacts is challenging. The study of environmental proxies in two different contexts, the Armorican Massif in North-Western Europe and the Saint-Pierre and Miquelon archipelago in North-Eastern Canada can unveil new insights to discuss this question. In this work we analyzed palaeoecological pollen and DNA proxies on different environmental archives. We observed through a conjoint review and meta-analysis the gradual opening of the Armorican landscape in response to the arrival of farming communities. The pollen-based climate reconstruction in this area put in evidence rapid climate variability and its influence on agro-pastoral activities. The study of ancient environmental DNA, through metagenomics strategies can complement pollen and archaeological data. Notably the use of bioinformatically designed probes in targeted capture enrichment hold the potential to retrieve diverse ecologically informative taxa. The application of these strategies in ombrotrophic peat bogs in Sain-Pierre and Miquelon notes the need to approach this type of archive with caution. To, conclude the work presented in this thesis allowed to enrich our knowledge on biodiversity dynamics during the agro-pastoral transition. It call for an enhanced transdisciplinary approach of environmental archives and pave the way for new palaeogenomic work on peatlands.



