Using a reference population yardstick to calibrate and compare genetic diversity reported in different studies: an example from the brown bear

In species with large geographic ranges, genetic diversity of different populations maybe well studied, but differences in loci and sample sizes can make the results ofdifferent studies difficult to compare. Yet, such comparisons are important for assessingthe status of populations of conservation concern. We propose a simple approach of using asingle well-studied reference population as a ‘yardstick'' to calibrate resultsof different studies to the same scale, enabling comparisons. We use a well-studied largecarnivore, the brown bear (Ursus arctos), as a case study to demonstrate theapproach. As a reference population, we genotyped 513 brown bears from Slovenia using 20polymorphic microsatellite loci. We used this data set to calibrate and compareheterozygosity and allelic richness for 30 brown bear populations from 10 differentstudies across the global distribution of the species. The simplicity of the referencepopulation approach makes it useful for other species, enabling comparisons of geneticdiversity estimates between previously incompatible studies and improving ourunderstanding of how genetic diversity is distributed throughout a species range.