Comparative functional head morphology in modern rove beetles (Coleoptera, Staphylinidae)

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With more than 63,650 described species, rove beetles (Staphylinidae) are one of the largest insect families. In contrast to phytophagous insects, rove beetles have diversified through their different ways of living in the litter layer. Extending our previous work on staphylinids methodically and conceptually, we follow, in the present project, an integrative functional and eco-morphological approach to investigating the comparative functional head morphology of modern, mostly predatory representatives of rove beetles. This refers to several species-rich monophyletic subfamilies of the traditional Staphylinine group. As part of a broad comparative analysis that also considers functional aspects, we aim at attaining a comprehensive understanding of the evolution and morphological diversification of these speciose clades. Based on Synchrotron microtomographic and scanning electron microscopic analyses of head morphology (mouthpart morphology, presence / absence of head muscles including their origins and insertions, structure and organization of the hypopharynx-prementum complex, structure of the tentorium, sclerites of the prementum), the functional aspects of mouthparts will be combined with direct observations of predatory and feeding behavior and interpreted in a phylogenetic context. We will examine comparatively 37 representatives of all subfamilies of the traditional Staphylinine group (and the main tribes for some). We will also gather morphometric data of the mandibles and the associated muscles to evaluate the relative mandibular biting forces and closing velocities. Three-dimensional geometric morphometrics will be used to quantify head morphological differences between clades and feeding types. Based on a phylogenetic scheme adopted from published sources, we will perform character mapping analysis with the goal of recognizing evolutionary changes and novelties including the resulting functional consequences. In order to perform a cladistic analysis, the head morphological characters established in the present project will be combined with a character matrix obtained from previous work of the applicant on other staphylinid clades. This will help to test the extent to which the internal head morphology can contribute to the clarification of open questions concerning the phylogeny among subfamilies and tribes within certain subfamilies. The analysis will also elucidate both the plesiotypic groundplan features and the autapomorphies of several subfamilies / tribes. Finally, by means of phylogenetic regression analyses, the biomechanical / functional morphological analyses of the mandibles will be related to the observations of prey-capture behavior, thereby facilitating the interpretation of patterns in a functional context and providing an understanding of the contribution of these characters to the diversification of these clades in general.