Genetic structure of the Cumbrian population is examined from data on gene and genotype frequency distributions, on geographical location, and on population movement in two generations.
The population is genetically heterogeneous; the central Lake District particularly, and also Carlisle and the southern periphery, stand out as distinct from the remainder and from each other. Regional subdivision of the population is sufficient to lead to some increased overall homozygosity, but its effect on inbreeding is considerably lower than the inbreeding level within regions, the latter being highest in the Lake District and the southern periphery. Examination of isolation by distance shows distance to be an important determinant of genetic differentiation in Cumbria; local and regional kinship levels are similar to those in alpine Swiss areas. Migration analysis suggests the distinctness of the west coast and southern periphery, and a slight increase in kinship between regions in the last generation.
The measures of genetic distance are closely correlated with each other. The measures of kinship derived from migration frequencies between regions are highly correlated with each other, and with geographical distance, but not with genetic distance. Present migration patterns are insufficient to account for the affinities within and between regions indicated by the genetic variation. It is possible that retention of Norwegian influence over a great length of time in the central Lake District is a major contributory element in present-day genetic heterogeneity in Cumbria.