I started the project by visiting the three main European herbaria that hold the largest collections of the focal Sideritis species, i.e. Copenhagen (CP), Lund (LD) and the Goulandris Natural History Museum (ATH) in Athens. In these collections, I examined more than 200 samples and obtained crucial information regarding the past distribution mountain tea in the Balkans. I additionally retrieved leaf samples for DNA extraction from 120 individuals. Using the information obtained from the visited collections, I defined field work and sampling strategy for the modern populations. The goal of the field work was to revisit the same populations for which herbarium material was already available. I then carried out extensive fieldwork during the summer of 2021 and sampled populations in a total of 16 mountains in Greece. Herbarium and modern samples were brought to Senckenberg Biodiversity and Climate Research Centre (SBiK-F) for further analyses. For developing the genome of Sideritis scardica, I obtained seeds from a commercial cultivator in Greece that grows plants of known origin, and grew several plants at climate chambers in SBiK-F. I selected a single individual from the cultivated plants and conducted three types of DNA sequencing, i.e. PacBio long-read sequencing, Illumina shotgun sequencing, and Dovetail chromosome conformation capture. The resulting high-quality draft genome of mountain tea is ~1.1Gb long and is distributed in ~600 scaffolds. Finally, we extracted DNA from 64 herbarium and 64 modern samples, resequenced these individuals using Illumina shotgun sequencing at 30x coverage, mapped resequenced samples onto the draft genome, and compared historical with contemporary genetic diversity. The final results for Work Package 1, i.e. inference of demographic history and estimation of genomic erosion in mountain tea populations are being currently compiled and are expected to be available before the end of 2022 and published within 2023.
For carrying out Work Package 2, high resolution climate and satellite data had to be compiled from various sources. To this end, I evaluated several alternative data sources and I finally obtained high-quality climate data for the last four decades using the ERA5 atmospheric reanalysis product from the European Centre for Medium-Range Weather Forecasts (ECMWF). These climate data were downscaled to match the resolution of satellite data using custom analytical pipelines developed for BEEP. Similarly, I evaluated several sources of satellite data and I chose the Landsat archive (30m spatial resolution) due to its high degree of data availability through time. I then combined climate and satellite data together with more than 900 georeferenced records that were collected during the intensive field work to estimate the extent of environmental changes through time, i.e. temperature and vegetation change, in the mountain tea habitats. I further conducted habitat suitability modelling to estimate changes in suitable habitats for the mountain tea. The results of the temporal environmental change are available and show a dramatic reduction in the suitable habitats of mountain tea as a result of global warming and mountain greening. These results are expected to be published within 2023.
The first outcomes of the BEEP projects have already been presented in international conferences and are under consideration for publication in high-profile scientific journals. I further communicated the results through teaching activities to students of all ages and levels, from primary school to international PhD courses for early career scientists.