Form-function relationships of head capsules of early split biting-chewing insects in a phylogenetic framework

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Winged insects such as dragonflies and mayflies (=Palaeoptera), grasshoppers and allies (=Polyneoptera) or barklice (=Psocodea) mostly possess biting-chewing mandibles of the same principal construction. In contrast to this relative uniformity in basic mouthpart construction, head capsules show a great variety in shape. The reasons for this head capsule shape diversity, its consequences for head biomechanics and finally its likely interplay with ecological factors are unknown. The project will therefore investigate the variety of different head capsule types within early biting-chewing insects mechanically, in order to assess how different head shapes influence overall mechanical performance and, finally, the evolutionary fitness of the head system. The overall hypothesis is that distinct morpho- and mechanospaces within biting-chewing insects exist, which are more dependent on the ecological niche than on common ancestry. Moreover it is expected that these distinct mechanospaces permited only a limited number of shape change trajectories during the evolution of biting-chewing.The 3D head shape variation of a wide range of Palaeoptera, Polyneoptera and Psocodea (>400 species) will be quantitatively analysed with geometric morphometrics. Biomechanical simulation will then be carried out on a subset (~43 species) covering the main head capsule morphotypes using multibody dynamics analysis and finite element analysis. Material property, muscle property, and bite force measurements will serve as input variables for the biomechanical modelling to ensure an accurate representation of in vivo mechanics in the in silico models. The project will furthermore take into account the general ecological niche such as food spectrum, hunting type, etc. in order to test their influence on head mechanics and shape variation in a phylogenetic framework. Finally, modelling of the theoretical mechanical performance landscape of biting-chewing in relation to the actual performance landscape occupied by real species will allow to identify head shape change trajectories and involved trade-offs during the evolution and diversification of the biting-chewing system. The results will thus refine our understanding of insect evolution, with the project identifying which mechanical factors made insects such extraordinarily successful feeders, and why and how their heads evolved into so many different types.