A demographic study of some populations in Shahrestan Nowshahr, Mazandaran, Iran, with reference to the genetic structure
The main objective of this thesis is to define the population structure of Shahrestan Nowshahr, Iran, by determining whether the population comprises one large, panmictic unit or small, localized breeding clusters, and the extent to which the pattern of mobility affects this structure. This study has been carried out by quantifying the nature and extent of migration within and from outside the study area. The components of analysis have included the past and. present demographic structure, the distribution and localization of dialects and languages, the spatial (matrimonial) and temporal (parent and offspring) continuity of gene flow, the orientation of movement, the extent of commonality of surnames and the pattern of relatedness and kinship within and among the subdivisions. The results have been used to assess the extent to which genetic mobility has been determined by geographic, demographic, linguistic and cultural constraints placed on the breeding size of the population. The consequences upon the genetic structure of the population in terms of departure from random mating and panmixia and the potential for genetic differentiation through local, selective pressures and random genetic drift have also been projected. Inferences from these analyses Indicate that the interaction of these factors have influenced and determined the migration pattern and the extent of the reproductive isolation of the Shahrestan. Shahrestan Nowshahr is not a homogeneous unit, but is composed of a series of local, partially isolated units with little genetic flow between them, thus limiting the size of the population, contributing to deviation from panmixia and conducive to random differentiation of local gene frequencies. The temporal increase in the range of movement indicates the breaking down of isolation, due to an overall change in the demographic, cultural and socio-economic structure of the population, providing greater possibilities for admixture and genetic homogeneity.