The bee-beetles‘ evolution

The genus of the bee-beetles (Coleoptera: Cleridae: Trichodes) occur in Africa, Asia, Europe and North America. They have colourful upper wings and are thus easy to recognize. The mostly red and black markings are thought to avert predators and may represent a typical case of mimicry, or more precisely, the feigning of poisonousness. The assumption came up because species from a genus of oil beetles (Meloidae), which is in contrast to the bee beetles actually poisonous due to its cantharidin content, look deceptively similar. However, this has never been proven and will be elucidated in this project. This will involve the reconstruction of the evolutionary lineages of the bee beetle species, which will then be chronologically dated with fossils. If the times of origin of similar wing colouration patterns of both genera are similar, this gives a good indication of co-evolution. To also infer the necessary spatial proximity, the distributions of the ancestors of both genera are reconstructed based on the distribution of contemporary species. This also enables the consolidation of biogeographical theories. Thus, new insights are expected as to why the Middle East is so rich in species of bee beetles. This may be because the genus originated there and many species persisted there, or because distribution ranges of species from the African, Asian and European continents meet there. The findings can be compared with those of other species groups and thus advance the formulation of general statements. State-of-the-art methods are used to achieve these goals. As collecting specimens becomes more difficult politically, DNA is extracted from animals in museum collections, which so far still presents challenges. Measurement of wing patterns will also be more accurate than previously by using 3D-models. In summary, the project aims to comprehensively elucidate the evolution of bee beetles, thereby advancing the promising use of historical DNA and new morphometric methods.

Treasures from the Museum: What Historical Beetles Reveal to Us Today Natural history collections are time capsules of biodiversity. Each specimen preserves information about where and when a species existed and what it looked like. Our project has contributed to our understanding of how to harness this knowledge using modern DNA analysis and what we can learn from it about the evolution of bee beetles (genus Trichodes). An important finding was that we now have a better understanding of how DNA degrades in museum specimens. Using numerous samples from collections, we were able to measure the extent to which DNA breaks down into small fragments and undergoes chemical changes over time. We identified factors that influence this process (age, preservation methods) and derived practical recommendations from them. For example, which samples are particularly suitable, how to handle them in the lab, and how to reliably analyze the data. Second, we developed methods for dealing with incomplete DNA data, as is common with historical insects. Our approaches allowed us to calculate reliable phylogenetic trees despite data gaps and to avoid errors. This helps not only with the beetles studied but also, more generally, with the use of museum collections for genetic studies. Third, our findings demonstrate why natural history collections are indispensable today: they contain a vast amount of information about past biodiversity and fill important gaps when species are rare, protected, difficult to find, or native to regions that are now barely accessible. In this way, museum specimens complement modern field research. For bee beetles, our data provided a clearer picture of their evolutionary relationships and the evolution of their diversity over time. This foundation is crucial for understanding why bee beetles are so strikingly colorful. Our findings support the idea that mimicry and aposematism played a central role: The striking colors may deter predators or emphasize the resemblance to defensive species. Museums are thus not only exhibition spaces but also research laboratories for life on Earth in the past and today. The findings will be published in several scientific articles. They address the quality and analysis of DNA from historical specimens as well as new insights into the evolution and color development of bee beetles.