Two genetically distinct populations of Varroa jacobsoni with contrasting reproductive abilities on Apis mellifera
Denis L Anderson; Stefan Fuchs
This paper demonstrates the presence of two genetically distinct populations of Varroa jacobsoni that show contrasting abilities to reproduce on Apis mellifera and can be identified easily using simple molecular techniques. When Australian- reared A. mellifera sister queens were transported to Germany and Papua New Guinea and established in varroa-infested colonies, the female V. jacobsoni in Germany readily reproduced on their brood whereas in Papua New Guinea they did not. These observations indicate that the cause of the reported inability of female V. jacobsoni to reproduce on A. mellifera in Papua New Guinea does not rest with the resident A. mellifera population. DNA sequences of a 454 base-pair region of the cytochrome oxidase subunit 1 (CO1) gene obtained from reproducing V. jacobsoni collected from A. mellifera colonies in Germany differed by 6.8% from similar sequences obtained from non-reproducing V. jacobsoni from A. mellifera colonies in Papua New Guinea. The presence of a Xho I restriction endonuclease (RE) site in the German but not in the Papua New Guinea sequences, and a Sac I RE site in the Papua New Guinea but not in the German sequences, allowed for the rapid identification of individual mites of the German (GER) and Papua New Guinea (PNG) genotypes. Further studies confirmed that non-reproducing female V. jacobsoni that were the only V. jacobsoni present in A. mellifera colonies in Java, Indonesia, prior to 1993 were of the PNG genotype. However, reproducing female V. jacobsoni that suddenly appeared in A. mellifera colonies in Java in 1993 were of the GER genotype. Following 1993, reproducing mites of the GER genotype and non-reproducing mites of the PNG genotype were detected in a single A. mellifera colony in Java and in another single colony in another region of Indonesia. These results clearly demonstrate that differences in mite genotype can explain observed differences and changes in the virulence of V. jacobsoni toward A. mellifera.