Morphometry of Lamiaceae pollen grains from the archaeological site of Kastrì (Epirus-Greece; 15th–16th cent. AD)

Abstract

Pollen analysis of a late medieval layer (15th–16th century AD) recovered in the archaeological site of Kastrì (Epirus, Greece) highlighted the occurrence of large amounts of stephanocolpate Lamiaceae pollen grains. Morphometric analysis, by means of Light and Scanning Electron Microscopy, allowed three different pollen types to be identified within the family. In particular, the structure of the bireticulate exine, which is only visible under SEM observation, revealed to be a diagnostic feature for genus and even species identification. This was possible thanks to comparison with modern Lamiaceae species that were selected on the basis of pollen morphological similarity and geographical distribution. The results of comparison, achieved through K-nearest neighbour classification, led to ascribe the subfossil pollen types to the genera Salvia, Mentha and Thymus and to propose S. nemorosa/glutinosa/pratensis, M. arvensis and T. praecox as the most probable species to be associated with the subfossil grains. The significance of such a large quantity of Lamiaceae pollen is not easy to decipher. However, the co-occurrence in the sample of grazing indicators would suggest that these aromatic herbs were probably related to feeding or caring for flocks, in line with the archaeological interpretation of the investigated medieval structure as a shelter for shepherds as well as with the current use of these plants as forage supplements.