Anthropometric variation and population structure of the island of Pag, Croatia

Human Biology, Apr 1994 by Smolej-Narancic, N, Chaventre, A, Rudan, P

The estimates of the minimum F sub ST, [i.e., the minimum levels of genetic divergence (Williams-Blangero and Blangero 1989)] gave us more explicit insight into the underlying genetic structure of the Pag population. The analysis was performed at the village, regional, and within-region levels. The minimum F sub ST value for the regional level is lower than the values for the village and the within-region levels, which implies that genetic divergence occurred primarily at the village rather than at the regional level. However, the minimum F sub ST for all nine villages is considerably higher than that for the villages within each region, indicating that the village divergence includes the interregional divergence, which is an important determinant of the island's population genetic structure. According to the endogamy estimate of 77%, the regional population groups are mutually considerably isolated. Their subdivisions, the village populations, are even more reproductively closed. Because the village populations are themselves small units of mating, a large amount of their divergence possibly arose from genetic drift that has operated for the past 13 centuries. This is not the case with the village populations in the eastern region of the island, whose lowest degree of divergence reflects a continuous influx of immigrants from the mainland in the past four centuries.

To corroborate the interpretation of intrapopulational morphological relationships within the context of village settlement history, we analyzed the mutual isolation, social relationships, and anthropometric-geographic-linguistic correspondences of the villages. Our initial hypotheses were (1) that anthropometry and linguistics would covary (Friedlaender et al. 1971; Sokal and Winkler 1987) and (2) that because geography has been shown to influence genetic structure (Malcot 1948; Jorde 1980; Zegura et al. 1990) and because the Mahalanobis distance matrix derived from phenotypic anthropometric traits represents a matrix of minimum genetic distances [as demonstrated by Williams-Blangero and Blangero (1989)], anthropometric distances would correlate positively with geographic distance. Both anthropometry-linguistic and anthropometry-geography relationships turned out as predicted. The results show that both geographic distance and dialect differences act as barriers to intrapopulational contacts, effecting morphological variation on the island. Strong isolation among the village populations (seen also through high endogamy in the western and northern regions) prevented their genetic homogenization through gene flow. According to the 13 village migration predictions, if the conditions remain stable, 26 more generations would be necessary for the homogenization of the entire island population (Sujoldzic et al. 1987). If the reproductively open Pag and Novalja populations are excluded from the analysis, the prediction might be even greater. Thus the current phenotypic morphological variation on the island--characterized by the population's division into three regional groups that are further subdivided into small village populations--reflects genetic variation, originated from ancestral differences, and has been retained because of marked geographic and social isolation.