Are genetically defined "metapopulations" self-evident in YHRD?

Area of Science:

• Forensic Genetics
• Population Genetics
• Bioinformatics

Background:

• The evidential value of Y-chromosomal short tandem repeat (Y-STR) matches in forensic genetics is typically assessed using population databases.
• The Y-chromosomal Haplotype Reference Database (YHRD) uses 'metapopulations' to represent diverse populations with presumed shared ancestry for match probability calculations.
• The validity of match probabilities depends on the database population being representative of potential trace donors.

Purpose of the Study:

• To investigate if the metapopulations highlighted in the YHRD are genetically self-evident within the database.
• To assess the genetic structure of YHRD and its correspondence to defined metapopulations.

Main Methods:

• Utilized classical cluster analysis on Y-STR profiles within the YHRD.
• Employed allele dissimilarity as the measure of pairwise distance between Y-STR profiles.
• Examined the relationship between genetic structure and marker mutation rates.

Main Results:

• A weak genetic structure was observed within the YHRD.
• The extent of genetic structuring was inversely proportional to the mutation rate of the Y-STR markers.
• YHRD could not be clearly divided into distinct subgroups that align with the database's highlighted metapopulations.

Conclusions:

• The current YHRD lacks sufficient genetic substructure to clearly delineate its defined metapopulations.
• Equating metapopulation frequencies with match probabilities requires clearer definitions and stronger justification for metapopulation use in forensics.
• Further research is needed to refine metapopulation definitions and validate their application in forensic Y-STR analysis.