The role of Earths climate, host-plant associations and adaptations to chemical defense compounds in
the species diversification of the weevil subfamily Ceutorhynchinae (Curculionidae, Coleoptera) a
combined phylogenomic and experimental approach:
About a quarter of the multicellular species on Earth are herbivorous insects, but it is still unclear how
this enormous biodiversity has originated. Phylogenetic analyses have shown that the interactions of
herbivorous insects with their host plants had an influence on speciation. Furthermore, it has been
proposed that climate changes have determined the radiation and distribution of insect groups. In order
to gain a deeper understanding of the specific impact of climate and host plant use on the radiation of
herbivorous insects, it is necessary to reconstruct phylogenetic relationships and divergence times in
order to estimate the impact of specific biotic factors (conservation of the host plant, host plant
changes and larval host plant use) and abiotic factors (historical climate changes). This research
project investigates the evolution of a subfamily of weevils (Ceutorhynchinae, Curculionidae,
Coleoptera). Host plants of the Ceutorhynchinae include garlic, aconite, poppy, and ephedra. Weevils
of the genus Ceutorhynchus, which alone account for about a quarter of all species of this subfamily,
use exclusively crucifers such as rape and cabbage as host plants, although these plants have a highly
effective chemical defense system against predators. If injured, mustard oil glycosides are degraded
enzymatically to reactive mustard oils, which are toxic to herbivorous insects. Some insects have
adapted to this so-called mustard oil bomb and can, for example, prevent mustard oil glycosides from
being converted into toxic degradation products. The aim of the project is infer the impact both
historical climate changes and specific host-plant uses on the radiation of Ceutorhynchinae. In order to
gain a deeper understanding of whether and how overcoming phytochemical barriers has actually
contributed to radiation, the project will investigate the detoxification mechanism of Ceutorhynchus
pallidactylus to find out how these beetles disarm the mustard oil bomb. To reconstruct the
phylogenetic relationships of Ceutorhynchinae and to further investigate the evolution of their
detoxification mechanisms, a novel approach combining modern transcriptome data sets and classical
molecular data sets is applied. The application of such a data set to evolutionary biology questions is a
novelty. This work will allow drawing a detailed picture of the evolutionary history of weevil-host
interactions, thus providing a stepping-stone to further elucidate insect diversity and phylogeny.