Joint-X: The role of coxa-trochanteral joints in beetle evolution revealed by quantitative synchrotron X-ray microtomography and (semi-)automatic image analysis

• Applicant: Dr. Thomas van de Kamp
• Subject Area: Systematics and Morphology (Zoology)
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518779777

Next-generation sequencing technologies revolutionized molecular phylogenetics and helped unravelling the evolutionary history of many insect groups. A major challenge remains the correlation of molecular and morphological data, which allows reconstructing the evolution of morphological characters. So far, the wealth of genetic data collected in recent years is hardly matched by comparative 3D morphological information and the immense morphological data available, e.g. in museum collections, remains largely unexplored. Modern 3D imaging techniques like X-ray microtomography are able to provide fascinating new insights into insect morphology, but most X-ray studies on insects are based on a very limited number of individual specimens. Thanks to synchrotron X-ray microtomography, we discovered in 2011 that weevil coxa-trochanteral joints closely resemble engineered screw-and-nut systems. Back then, both scanning and data analysis were very time-consuming, effectively impeding a systematic study on a large sample series. As recent progresses in high-throughput X-ray imaging and image analysis now facilitate large-scale digitization on insect 3D morphology, we now have the prerequisites required for a comprehensive study on beetle coxa-trochanteral joint evolution. Within this project Joint-X, we will tackle this challenge by employing state-of-the art quantitative synchrotron X-ray microtomography, (semi-)automatic image segmentation and convolutional neural networks. Employing 3D geometric morphometrics and phylogenetic comparative methods, we will correlate hundreds of morphological 3D datasets to phylogenetic trees, allowing us to identify key events in evolution and trace the transformation from the simple hinge joint in Adephaga into one of the most unique morphological characters in beetles – the “biological screw”. We will describe the major patterns of joint evolution within the order, analyze variations of the screw joint within Curculionidea, characterize joint functionality and correlate morphological data with molecular and ecological information. A secondary result of this project will be a comprehensive collection of 3D morphological datasets of beetles, which will be made available to the public via an open online repository and will probably constitute the largest collection of beetle 3D data available. This data can be used by the scientific community to study other morphological characters and to correlate them with other types of data.

• DFG Programme: Research Grants