Many closely related weevil species live mono or oligophagously on host plants of the same families. This pattern suggests a principal correlation between specific host plant use and differential taxonomic diversity. In some cases, this may lead to a high diversity of weevils and also to the emergence of cryptic species. In combination with their often uniform appearance, this make many weevil groups a taxonomic and systematic challenge. Consequently, the taxonomic status of many genera and tribe still remain uncertain.

Therefore, molecular biological methods were used in this project to establish a comprehensive phylogeny of the subfamilies Ceutorhynchinae (Curculionidae) and Apioninae (Brentidae) and to investigate the evolution of their host plant use in more detail. In addition to the compilation of the most detailed phylogeny of these groups to date, a temporal correlation between the radiation of the two subfamilies and the evolution and distribution of the flowering plant families used could be confirmed. For the Apioninae, these patterns could be dated to the Cretaceous period. The diversification of the Ceutorhynchinae can also be traced back to major climate changes since the Eocene. For the project also COI sequences of 54 species from Austria were created, which are available on BOLD for future projects. The barcoding of native weevils will be continued as part of student courses at the University of Vienna in the future.

In a follow-up project (FWF P-32029), we will investigate how the cabbage stem weevil (Ceutorhynchus pallidactylus), overcomes the chemical defence mechanisms of its host plants (Brassica oleracea). Furthermore, we will investigate how the use of this new resource has influenced the evolution of the genus Ceutorhynchus, i.e. whether and how the overcoming of this phytochemical barrier has contributed to possible rapid radiations in this genus.