Genetic structure of the saguenay, 1852–1911: Evidence from migration and isonymy matrices

Abstract

The Saguenay is a region in northeastern Québec populated in the second half of the 19th century through migration from other parts of Québec. The present-day population of nearly 300,000 is the result of both immigration and high rates of intrinsic growth. This population has been of interest to geneticists because of the high incidence of certain hereditary diseases, notably spastic ataxia, tyrosinemia, agenesis of the corpus callosum, vitamin D-dependent rickets, and myotonic dystrophy. Parent-offspring migration and isonymy matrices were used to estimate random kinship using the Malécot model for six 10-year time periods from 1852-1911. Comparisons between two estimates of kinship--one from parent-offspring migration matrices (phi) and the other from isonymy (R)--and geographic distance were made using both product-moment and Mantel correlation. Comparisons of within- and between-subdivision kinship were made using nonparametric and Mantel correlation. Within-subdivision kinship from the phi matrix was also compared with kinship estimated from marriage dispensations for endogamous marriages. The estimates of random kinship from the parent-offspring matrices showed a good fit with geography. However, isonymy did not correlate well with geographic distance; and phi and R showed no correlation until the last two time periods, and the diagonal of phi did not correlate with the marriage dispensations. Examination of scatterplots of phi vs. R suggests that nonrandom migration during the process of settlement formation is responsible for the lack of correlation. While movement across space seems to be highly dependent on distance, nonrandom selection of migrants means that between-subdivision estimates of kinship based on migration are not congruent with those obtained by other methods. On the whole, genetic differentiation seems to have been low due to the high levels of movement between subdivisions and immigration. The weak dependence of genetic structure on geographic distances in the present population is demonstrated by mapping the geographic distribution of cases of three recessively inherited diseases.

Heritability Estimates of Obesity Measures in Siblings With and Without Hypertension

“…Because of little migration thereafter and relatively high growth rates, this population today represents one of the largest isolated populations in North America. 26 Several monogenic disorders have been shown to have a high prevalence in this population. 25 For some of them, a founder effect has been identified.…”

“…26 This population originates from a relatively limited number of ancestors of French descent who migrated to this region in the 19th century. Because of little migration thereafter and relatively high growth rates, this population today represents one of the largest isolated populations in North America.…”

Genome-Wide Scan for Linkage to Obesity-Associated Hypertension in French Canadians

“…13 In brief, the families were selected from a geographically remote population of French-Canadian origin living in the SLSJ region. 14 The population originates from ancestors of French descent who migrated to this region in the early 19th century. The population has experienced high intrinsic growth, from 5200 inhabitants in 1852 to 285 000 at present.…”

Sur la distribution spatiale des gènes délétères dans la région du Saguenay (XIXe et XXe siècles)

“…L'étude des matrices migratoires parents-enfants en est une bonne illustration (cf. Jorde, 1982;Gradie et al, 1988). Sur un second plan, qui relève de la recherche appliquée, on s'intéresse en particulier à la diffusion de gènes délétères afin de localiser le risque des génopathies dans une population.…”