BACKGROUND: In the Iberian Peninsula, the Mirandese dialect, spoken in Miranda do Douro (Portugal) close to the north-eastern border with Spain, has attracted much attention. Aim, subjects and methods: This study focuses on providing further insight into the connections forged between Miranda do Douro and regions in the nearby Province of Zamora. This is in order to better assess the extent to which such relations could have been detained by the current patterns of genetic diversity of the populations, whilst contributing to refining the knowledge on patterns of micro-differentiation within the Peninsula. The genetic characterization of both populations was performed through the analysis of X-chromosomal markers: X-STRs and X-indels.

RESULTS AND CONCLUSION: The results showed that Miranda do Douro tended to present slightly lower levels of diversity in comparison to the other studied regions, which can be a discreet sign of isolation of that population over the years that might have led the way to the preservation of a language not spoken anywhere else in the country. The analysis of X-STRs particularly brought to light the presence of a subtle population sub-structure at the micro-geographical area encompassing the north-eastern border, which seems to portray the importance of the political border as a mechanism withholding gene flow between the two countries.