Morphological and genetic studies of waterlogged Prunus species from the Roman vicus Tasgetium (Eschenz, Switzerland)

Morphological and genetic studies were performed on waterlogged Prunus fruit stones from the Roman vicus Tasgetium (Eschenz, Switzerland). Some fruit stones could be identified to species level based on morphological and metric criteria. Other fruit stones found were not identifiable to species level. Of the latter, the morphological group Prunus insititia/spinosa represents either native sloe, cultivated primitive plum (damson) or a hybrid of both. In one out of 10 individual fruit stones of this group Prunus specific chloroplast trnL-trnF and nuclear ITS1 markers were verifiably amplified. Sequences of trnL-trnF led to the identification of Prunus spinosa. The presence of authentic DNA was confirmed by phylogenetically meaningful sequences from the archaeobotanical group Prunus avium/cerasus of the same sample using chloroplast rbcL and nuclear ITS1 DNA markers. The results demonstrate the utility of waterlogged plant remains for genetic analysis: as seeds of fruit trees are often preserved waterlogged in the archaeological record. Ancient DNA (aDNA) studies are a promising tool to answer archaeobotanical issues concerning early horticulture, which probably started in the Northern alpine region with the onset of Romanisation.