Distribution, mechanisms and evolutionary significance of clonality and polyploidy in weevils


Per Stenberg. Tel.: +46 0907854344; fax: +46 090771420; e-mail: Per.Stenberg@molbiol.umu.se


Abstract  1 Genetical mtDNA relationships of 41 taxa of weevils were examined using cladistics. Ingroup taxa belong to Otiorhynchus scaber and O. nodosus and outgroup comparison was made with O. singularis. All three species are minor forest pests.

2 Otiorhynchus scaber specimens are either diploid sexuals or diploid, triploid and tetraploid clones, from two different populations (Slovenia and Austria) that belong to two different evolutionary lineages. Otiorhynchus nodosus specimens are tetraploid clones. Both species show geographical parthenogenesis, as do many other Otiorhynchus species.

3 Mitochondrial data indicate that O. nodosus clones are more closely related to Slovenian sexuals of O. scaber than these are to sexuals from Austria. It also shows that almost all clones of O. scaber collected in one of the two regions where sexuals are found are more closely related to sexuals from the other region.

4 Three different hypotheses that may explain the distribution of O. scaber, mechanisms important for the evolution of the clones and implications of the presence of Wolbachia are discussed.

5 We conclude that parthenogenesis is likely to be linked to hybridization in O. scaber and that hybridization events between ancestors of O. nodosus and O. scaber are the probable cause of the presence of O. nodosus in the ingroup. We also find that polyploid clones are superior colonizers compared to sexuals and diploid clones, in O. scaber.

6 The results suggest that systems where both sexuals and clones exist are more complex than previously suggested. The mapping of genetic variation in clonal complexes and the tracing of clonal origins may be useful in pest management.