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Geographical structuring in the mtDNA of Italians
G Barbujani1, G Bertorelle, G Capitani
1Dipartimento di Scienze Statistiche, Università di Bologna, Italy.
Summary
Mitochondrial DNA (mtDNA) analysis reveals genetic clines and population expansions in Italy and Sicily, but not Sardinia. Most genetic variation is found within populations, not between them, suggesting isolation by distance and past demographic shifts.
Area of Science:
- Population Genetics
- Molecular Anthropology
- Human Evolutionary Studies
Background:
- Mitochondrial DNA (mtDNA) variation provides insights into human population history and migration patterns.
- Spatial autocorrelation methods are effective for analyzing geographical genetic structures.
Purpose of the Study:
- To investigate geographical patterns of mtDNA variation in Italian populations.
- To identify clinal patterns, population structure, and demographic events using spatial autocorrelation.
Main Methods:
- Analysis of mtDNA restriction morph frequencies in 12 Italian samples (1072 individuals).
- Application of two spatial autocorrelation methods, including the autocorrelation index for DNA analysis (AIDA).
- Partition of gene diversity (GST) and neutrality tests (Tajima's test).
Main Results:
- Observed North-South clines and differences between Sardinia and mainland Italy, consistent with isolation by distance.
- Most genetic variability (94.3%) was found within populations (GST = 0.057), with minor differences between them.
- Evidence suggests rapid population size increases in Italy and Sicily (8000-20,500 years ago), but not in Sardinia.
Conclusions:
- Italian mtDNA variation reflects clinal patterns and past demographic expansions, particularly in the Neolithic and Paleolithic periods.
- Sardinia's genetic landscape appears less impacted by these major demographic events compared to the Italian peninsula and Sicily.
- mtDNA data supports distinct evolutionary trajectories for mainland Italian and Sardinian populations.