Genetic Depletion in the European Bison (Bison bonasus) and the Significance of Electrophoretic Heterozygosity for Conservation

Starch gel electrophoresis was used to screen 35 lowland bison from the herd in the Biażlowieża Primeval Forest for genetic variation at 69 presumptive structural loci. Average heterozygosity ( H = 1.2%) proved to be three times lower than that based on 20 loci ( H = 3.5%) reported in a previous study by other authors. These earlier results were interpreted as evidence that the passage of the species through an extreme genetic bottleneck (12 founder genomes) had not had much influence on genetic variation. A comparison of estimates of H and the proportion of polymorphic loci ( P ) among different species or populations of Artiodactyla revealed that P was the only parameter to be significantly reduced in those that had experienced genetic bottlenecks. However, the data also show that, in spite of similar H values in species or populations with or without bottlenecks, average heterozygosity is only useful as an indicator of overall genetic variability in the latter. To draw conclusions about genetic depletion on the basis ofelectrophoretic data, we strongly recommend that H , together with its variance among a large number of loci, and additional parameters such as P and the ratio H:P be taken into account.