Professur für Forstzoologie und Entomologie Albert-Ludwigs-Universität Freiburg i.Br. Professur für Forstzoologie
und Entomologie
Albert-Ludwigs-Universität Freiburg i.Br.

Professur für Forstzoologie
und Entomologie
Freiburg i.Br.

Evolution of danaines' relationships to plants

Neglecting associations to flowers for obtaining nectar, danaine butterflies exhibit a dual relationship to plants: on the one hand, their larvae require specific hostplants (primary host associations). On the other hand, adults (often only the males) require pyrrolizidine alkaloids (PAs) from plants usually unrelated to the larval hostplants (secondary host associations).
This dual insect-plant relationship and the peculiar significance of hostplants' secondary metabolites make Danainae an ideal system to study the role of sequestration of secondary plant chemicals in an evolutionary perspective.

Analysis of apocynad larval hostplants of milkweed butterflies (Lepidoptera: Danainae) in search for pattern
This joint project with Prof. Dr. Sigrid Liede-Schumann of the University of Bayreuth analyses the hostplant records of Danainae in the light of new knowledge of the phylogeny of Apocynaceae s.l..

Utilization of larval hostplant chemicals in Danainae (Lepidoptera)
This joint project with Prof. Dr. Ulrich Mebs of the University of Frankfurt addresses the open question of sequestration of cardenolides in Euploea as part of a wider study on danaine genera previously not studied from a chemoecological point of view.

Petschenka G, Fandrich S, Sander N, Wagschal V, Boppré M, Dobler S (2013) Stepwise evolution in the Na+/K+-ATPase of milkweed butterflies (Lepidoptera: Danaini). Evolution: in press

Despite the monarch butterfly (Danaus plexippus) being famous for its adaptations to the defensive traits of its milkweed host plants, little is known about the macroevolution of these traits. Unlike most other animal species, monarchs are largely insensitive to cardenolides, since their target site, the sodium pump (Na+/K+-ATPase), has evolved amino acid substitutions which reduce cardenolide binding (so-called target site insensitivity, TSI). Since many, but not all, species of milkweed butterflies (Danaini) are associated with cardenolide-containing host plants, we analyzed 17 species, representing all phylogenetic lineages of milkweed butterflies, for the occurrence of TSI by sequence analyses of the Na+/K+-ATPase gene and by enzymatic assays with extracted Na+/K+-ATPase. Here we report that sensitivity to cardenolides was reduced in a stepwise manner during the macroevolution of milkweed butterflies. Strikingly, not all Danaini typically consuming cardenolides showed TSI, but rather TSI was more strongly associated with sequestration of toxic cardenolides. Thus, in line with current theory, tri-trophic interactions appear to exert a dramatic effect on the evolution of both plant and herbivore species.