The population structure of the winter moth Operophtera brumata in relation to local adaptation and habitat fragmentation

This study aimed at investigating the importance of natural selection, genetic drift and gene flow on the distribution of genetic variation in the winter moth. I investigated two levels of presumed genetic isolation, local variation in selection pressures on different hosts (adaptive deme formation) and habitat fragmentation. The genetic population structure was investigated indirectly with allozyme polymorphisms at 5 loci and directly by density and fitness estimation.; The analyses showed that natural selection is an important evolutionary force in the adaptive deme formation of the winter moth on pedunculate oak. Up to 25% mortality appears to occur as a result of maladaptations to individual hosts. As a result of variation in individual quality, adaptive male mate choice appeared to have evolved. Habitat fragmentation appeared to increase genetic differentiation (F{dollar}rmsb{lcub}st{rcub}{dollar} = 0.03) and to decrease within population genetic diversity by up to 30%. The importance of these effects, and the use of fluctuating asymmetry and deviations of genotype distributions from Hardy-Weinberg equilibrium as a measure of inbreeding depression, are discussed in relation to conservation biology.