The effective family size of immigrant founders predicts their long-term demographic outcome: From Québec settlers to their 20th-century descendants

Investigating temporal bone variation of colonial populations from St-Lawrence Valley, Quebec: A 3D geometric morphometric approach

OBJECTIVES

In Quebec, genetic and genealogical research are used to document migratory events and family structures since colonial times, because bioarchaeological analysis is limited by poor skeletal preservation. This article aims to fill this gap by exploring past population structure in the St-Lawrence Valley from the French (1683-1760) and British (1760-1867) regimes using morphological variation of well-preserved temporal bones.

MATERIALS AND METHODS

3D geometric morphometrics shape data from seven populations (five Catholics of French descent and two Protestants of British descent; n = 214) were collected from temporal bones. Using Procrustes distances and both MANOVA and Discriminant Function Analysis, morphological differences were measured to calculate affinities patterns among populations. Shape variations were explored with between-group analysis, Mahalanobis distances and quantified by means of Fst estimates using Relethford-Blangero analysis.

RESULTS

Despite strong affinities between all Catholic cemeteries, all show divergent morphological regional diversity -especially Montreal and the fortified villages dedicated to its defense. Montreal exhibits low increase in morphological variance over three centuries. As our results show no morphological differences between the Catholic and the Protestant cemeteries in Montreal, this fact may highlight the potential presence of Irish or admixed individuals in Montreal cemeteries after the British takeover.

DISCUSSION

Patterns of morphological diversity highlighted that French colonists did not equally contribute to the descendant populations as reflected by significant interregional variation. Although historical records show that French and English-speaking populations did not tend to admix, morphological affinities between Protestants and Catholics in the beginning of the industrial era in Montreal could reflect the genetic contribution of Catholic Irish migrants.

RESEARCH HIGHLIGHTS

All Catholic cemeteries display distinct morphologies, highlighting differential contributions from French colonists and founder effects, which have increased regional differences. Montreal Catholic (French descent) and Protestant (English colonists) cemeteries show significant morphological affinities at the beginning of the industrial era. The Irish migration following the British conquest may explain morphological similarities observed between Catholic and Protestant cemeteries.

On the genes, genealogies, and geographies of Quebec

Population genetic models only provide coarse representations of real-world ancestry. We used a pedigree compiled from 4 million parish records and genotype data from 2276 French and 20,451 French Canadian individuals to finely model and trace French Canadian ancestry through space and time. The loss of ancestral French population structure and the appearance of spatial and regional structure highlights a wide range of population expansion models. Geographic features shaped migrations, and we find enrichments for migration, genetic, and genealogical relatedness patterns within river networks across regions of Quebec. Finally, we provide a freely accessible simulated whole-genome sequence dataset with spatiotemporal metadata for 1,426,749 individuals reflecting intricate French Canadian population structure. Such realistic population-scale simulations provide opportunities to investigate population genetics at an unprecedented resolution.