Genetic changes in a vendace Covegonus albula (L.) population, 92 years after introduction

The Osensjmn vendace, Coregonus albula (L.), population was founded in 1895 by introduction of about 90 000 fry from Lake Mjøsa. After 92 years, or about 46 generations of isolation, remarkable genetic changes were evident among the transplants compared to their source population. Electrophoresis of 33 enzyme loci revealed that allele frequencies differed significantly in eight of the 10 polymorphic loci. Nei's unbiased genetic distance was D = 0.012, representing the level of population differentiation usually observed among distant watercourses in vendace. Genetic variability was clearly higher among the transplants: average observed heterozygosity was 14.8% compared with 11.2% among Lake Mjøsa vendace. The high genetic variation among Osensjoen vendace shows that the divergence is not due to a small number of founders or bottlenecks in later generations. Selection by the contrasting environmental conditions between the habitats of the donor and transplanted populations is the most plausible hypothesis to explain the genetic changes in the Osensjsen vendace.