Ecology and Evolution of Cooperative Fungiculture in Beetles

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Cooperation is ubiquitous in nature and its evolution has challenged generations of evolutionary biologists. Today many principles of social evolution are widely accepted, but major issues remain unsolved. For example, the strongest approach in evolutionary biology, namely experimental evolution of a trait, has not been accomplished for social behaviour in animals. Likewise, while the ecological factors that select for intraspecific sociality are relatively well known, it is unclear if there are specific factors that consistently facilitate the evolution of interspecific mutualisms. Bark- and ambrosia beetle species are excellent models to address these questions. The reason is that many of these species grow fungi for food - a trait which has independently evolved at least ten times in this group. Most interestingly, the evolution of this fungiculture was always accompanied by the evolution of more complex social organization. Thus, many farming species are at the transition from a sub-social to a eusocial lifestyle, which is quite rare in animals. I have developed an artificial rearing and observation technique, suitable for many bark- and ambrosia beetle species, which now allows me to directly test how certain ecological conditions affect the evolution of social behaviours and the mutualism with fungi. Additionally, we can learn a lot on the mechanisms of animal farming, which is comparable to human agriculture in many ways.In this Emmy Noether project, I will tackle major unsolved issues in social evolution and mutualism, using ambrosia beetles as a model. My main objectives are to (i) conduct experimental evolution of less and more social beetle strains by selecting on timing of beetle dispersal and manipulating pathogen pressure, (ii) test the effects of the co-selected fungal community on social behaviour and study trade-offs between social behaviour, reproduction, and dispersal, (iii) investigate social polymorphisms and how they are affected by habitat characteristics and symbiont communities, (iv) determine if division of labour in beetles is chemically regulated, (v) examine if beetles can actively control fungus communities, identify the mechanisms of nest defence against pathogens and of induction of the fruiting of the fungi by means of mutualistic bacteria, and (vi) establish a dialogue between researchers working with farming insects and agronomists to compare farming practices from an evolutionary perspective, and stimulate novel research. To achieve all these objectives, my group will apply an interdisciplinary approach, combining selection experiments, experimental assays, and culturing methods with state-of-the-art molecular (e.g. qPCR, next-gen-sequencing) and biochemical (e.g. GC-MS) techniques. Würzburg is the preferred place for this project as this environment unifies tremendous expertise on social insect behaviour, evolution and chemical ecology (including fungus-farming ants), offering excellent collaborations.