Population Genetics of Spruce Bark Beetle Ips typographus (Col., Scolytidae) and Related Ips Species1

Enzyme electrophoresis proved to be a useful method to study population genetic aspects in Ips typographus (L.) because of three highly polymorphic loci. Aspartate aminotransferase locus-2 (Aat-2), physiologically involved in the transfer of aminogroups, has six alleles per population. Amylase locus1 (Amy-1), physiologically involved in the hydrolysis of starch, has 10 alleles per population, and esterase locus-2 (Est-2), physiologically involved in processes of detoxification and the metabolism of juvenile hormone, has 16 alleles per population. The allozymes, pattern, and the mode of inheritance of nearly all alleles were genetically proved. The different amount of alleles among allozymes could reflect the physiological role of the enzymes (Johnson 1974); therefore most studies were calculated individually (Stauffer and others 1992b). A related but distinctly different species is the spruce bark beetle Ips amitinus. This relationship could be also demonstrated by enzyme electrophoresis. The existence of I. amitinus and I. amitinus var. montana (Fuchs 1913), which appeared to be doubtful, was investigated by behavioral, morphological and biochemical (cuticular analysis and enzyme electrophoresis) techniques. Because no obvious differences between the two races could be found, the distinction of a var. montana becomes very unprobable (Zuber and others 1992). Efficiency of a commercial pheromone product, which is commonly used in central Europe for trapping I. typographus, proved to be regionally different. A genetic basis of these differences was assumed. Seventeen European populations of this species, collected from infested logs, were studied. The dendrograms and an Alscal analysis of Aat-1 and Est-2 clustered three groups―the northern (Scandinavian) populations, the southern (alpine) populations, and the middle European (prealpine/Czechoslovakian) populations. Distribution of these three genetic groups corresponds to the three parts of natural distribution of the host tree, Picea abies, in Europe, each of