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To genetically reconstruct the demographic history of the human population of Corsica (western Mediterranean), we analyzed the variability at eight autosomal STR loci (FES, VWA, CSF1PO, TH01, F13A1, TPOX, CD4, and D3S1358) in a sample of 179 native blood donors from 4 out of the 5 administrative districts. The main line of genetic discontinuity inferred from the spatial distribution of STR variability overlapped the linguistic and geographic boundaries. In the innermost areas (Corte district) several estimators had larger stochastic effects on allele frequencies. Genetic distance measures underlying different evolutionary models all pointed to a higher variability within Corsicans than within the rest of the Mediterranean reference populations. All Corsican subsamples showed the highest distance with a pooled sample from central Sardinia, thus making recent gene flow between the two neighboring islands unlikely. Hierarchical AMOVA and distance-based multivariate genetic spaces stressed the closeness of Tuscan and Corsican frequency distributions, which could reflect peopling events with different time depths. Anyway, estimated separation times well support the linguistic hypothesis that Neolithic/Chalcolithic events have been far more important than Paleolithic or historical processes in the shaping of present Corsican variability.

Seven Y-chromosome microsatellite loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393) were analyzed in three populations from sub-Saharan Africa: the Bamileke and Ewondo populations from Cameroon and the Hutu from Rwanda. Complete typing was obtained for 112 individuals, and a total of 53 different haplotypes was observed. The single-locus gene diversity, averaged across populations, ranges from 0.100 for the DYS392 locus to 0.610 for the DYS389I locus. The haplotype diversity ranges from 0.832 (Ewondo) to 0.965 (Hutu), with an intermediate value of 0.918 in the Bamileke. The diversity among Bamileke, Ewondo, Hutu, and other sub-Saharan populations selected from the literature was analyzed using both a classical (F(ST)) and a stepwise-based (R(ST)) genetic distance method. The pattern of interpopulational diversity based on F(ST) was congruent with anthropological knowledge, while that based on R(ST) revealed unexpected and unconvincing population affinities. From a practical point of view, our study indicates that Y-chromosome microsatellite data may provide useful information for analyses of interpopulational diversity among sub-Saharan populations if an adequate number of loci and individuals along with an appropriate genetic distance method are used. On a theoretical ground, we propose that the lesser performance of R(ST) compared to F(ST) could be explained by the important role played by genetic drift in shaping the relationships among examined populations.

The genetic structure and interrelationships of six populations of the Garfagnana valley (Tuscany, Italy) were examined using chromosomal heteromorphisms concurrently with blood group system, red cell isozyme, and serum protein polymorphisms, secretor status, and surname frequency data. We aimed to evaluate the relationship of cytogenetic polymorphisms to more classical sources of gene frequency data in a population with a well-known demographic scenario. The R matrix technique (Harpending and Jenkins 1973) was used to estimate kinship coefficients, and the Harpending-Ward model (1982) and its extensions for quantitative traits (Relethford and Blangero 1990) were used to detect differential systematic pressure among population subdivisions. Mantel statistics were used to assess the significance of the correlations between cytogenetic, genetic, isonymy, geographic, and migration matrices. The analyses consistently gave similar results for the DA/DAPI cytogenetic heteromorphism and most gene frequency data. Both sets of results depend on migration patterns and on geographic distance among population subdivisions. However, C cytogenetic heteromorphism and some separately analyzed genetic markers did not fit the demogeographic pattern. Overall, it appears that data from different levels of the genetic hierarchy (namely, DNA regions encoding for classical biochemical markers and the noncoding highly variable cytogenetic bands of heterochromatin) can be treated and compared using the same analytical tools.

DA/DAPI and C chromosomal heteromorphic sites (1q, 9q, 15p, 16q, Yq) in a sample of 136 unrelated individuals from the Garfagnana valley (Tuscany, Italy) have been analyzed quantitatively and qualitatively. The variations in length, between-homolog heteromorphisms, and intensity of fluorescence of the heterochromatic bands have been compared in two subsamples of the population (upper and middle valley) individualized according to geodemographic criteria. DA/DAPI heterochromatin differed significantly from C heterochromatin, showing a lower average amount and a higher variability at each site. This suggests a differential staining of DNA of the two banding systems. Furthermore, DA/DAPI heterochromatin was less uniformly distributed in the population than C heterochromatin and the regions 16q and Yq discriminated better between subsamples. The variations of DA/DAPI fluorescence at the 15p site demonstrated an excess of homomorphic individuals in the upper valley, which could be related to the mating structure of the population living in this area.