Beyond Introgression: Assessing Genetic Diversity and Population Structure in the Brugse Vechter
AOBA Scientific Report – Phase II
Abstract
The first phase of AOBA's genomic research demonstrated that the contemporary Belgian Brugse Vechter population contains varying degrees of historical introgression from Sumatra, Malay and commercial meat-type chickens, while the Colonial Bloodlines retained substantially higher genomic continuity.
However, identifying introgression alone does not provide a complete understanding of the breed's genetic health.
The second phase of AOBA's research programme will therefore focus on genetic diversity, population structure, and the long-term sustainability of the Brugse Vechter. The objective is to distinguish between historical genetic continuity, founder effects, genetic drift and inbreeding, thereby providing a comprehensive scientific basis for future conservation breeding.
Introduction
The conservation of a heritage breed requires more than identifying foreign genetic contributions.
A genetically authentic breed must also retain sufficient genetic diversity to remain healthy and sustainable over future generations.
Although the first phase of AOBA's genomic research successfully identified historical introgression, it also raised additional scientific questions regarding the genetic structure of both the Colonial Bloodlines and the Belgian population.
Consequently, AOBA has initiated a second phase of research focusing on population genetics rather than ancestry alone.
Why Genetic Diversity Matters
Genetic purity and genetic diversity are not synonymous.
A population may display very limited foreign introgression while simultaneously suffering from reduced genetic diversity caused by founder effects, genetic drift or prolonged breeding within a limited number of families.
Conversely, a genetically diverse population may contain historical introgression from other breeds.
For responsible conservation breeding, both aspects must be understood simultaneously.
The objective of AOBA is therefore not merely to preserve the historical genome of the Brugse Vechter, but also to ensure that this genome remains genetically healthy and viable.
Research Objectives
The second phase of the project aims to answer several fundamental questions.
- How much genetic diversity remains within the Colonial Bloodlines?
- Does genomic homogeneity represent historical continuity or founder effects?
- What is the effective population size of each bloodline?
- What degree of relatedness exists between breeding families?
- How much historical genetic variation has been preserved?
- Which breeding strategies best maintain both authenticity and genetic health?
Population Genetic Analyses
To answer these questions, AOBA intends to expand its genomic analyses using internationally recognised population genetic methods.
These include:
- Observed and Expected Heterozygosity (Ho and He)
- Runs of Homozygosity (ROH)
- Inbreeding Coefficients (FIS)
- Identity-by-Descent (IBD)
- Genomic Relationship Matrices
- Effective Population Size (Ne)
- Kinship Coefficients
- Principal Component Analysis (PCA)
- Phylogenetic reconstruction
- Whole Genome Sequencing (WGS)
Together, these analyses will provide a far more comprehensive understanding of the genetic architecture of the Brugse Vechter.
Building a European Reference Population
Another objective of Phase II is the establishment of a comprehensive European reference population.
Future comparative analyses should include:
- Colonial Brugse Vechter Bloodlines
- Modern Belgian Brugse Vechter
- Combattant du Nord
- Luikse Vechter
Additional historical European gamefowl breeds may be incorporated where historical evidence supports their relevance.
These comparisons may help identify the ancestral genomic components shared by historical European gamefowl and contribute to reconstructing the original Brugse Vechter genome.
Understanding Historical Change
The evolution of a breed is influenced by multiple biological processes.
Historical introgression represents only one of these mechanisms.
Equally important are:
- founder effects;
- genetic drift;
- natural selection;
- artificial selection;
- demographic bottlenecks.
Understanding the relative contribution of each process will allow conservation breeding programmes to distinguish between genuine historical characteristics and changes that accumulated during recent breeding history.
Conservation Breeding
The purpose of this research is not to criticise breeders or previous breeding decisions.
On the contrary, the remarkable dedication of generations of breeders has ensured the survival of the Brugse Vechter.
The role of modern genomics is to provide objective scientific information that supports future breeding decisions.
By combining traditional breeding expertise with contemporary genomic technologies, conservation programmes can preserve both historical authenticity and long-term genetic health.
Future Perspectives
AOBA envisions the establishment of one of the most comprehensive genomic databases ever created for a European heritage gamefowl breed.
Future research may include:
- expansion of Colonial Bloodline sampling;
- international genomic collaboration;
- ancient DNA comparisons where historical specimens are available;
- Whole Genome Sequencing;
- development of genomic breeding recommendations;
- establishment of a long-term conservation management programme.
Conclusion
The first phase of AOBA's research identified historical introgression.
The second phase aims to answer an equally important question:
How genetically diverse and sustainable is the remaining historical Brugse Vechter genome?
Only by integrating ancestry analysis with population genetics can conservation breeding move beyond preserving appearance alone and begin preserving the complete biological heritage of the breed.
AOBA believes that the future of the Brugse Vechter lies not only in maintaining its historical identity, but also in safeguarding the genetic diversity necessary for its continued survival.
