Palaeo-Evo-Devo of Insecta – the amber forest as a major source of information for reconstructing the evolutionary history of an ecologically important group

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Insecta is one of the dominating animal groups today, in terrestrial as well as in freshwater ecosystems. However, insect diversity is currently endangered as different studies have shown. To enhance our understanding on the processes leading to the diversity loss, similar processes in past ecosystems can provide crucial information. Such information can be retrieved from the fossil record. In the focus of this project are insects preserved in amber. Amber can preserve morphological structures to a very high degree of detail, comparable to that in insects living today. Yet, the diversity of Insecta is not only represented by its large species richness, but especially by its morphological diversity. This becomes very apparent when not only adult forms, but also earlier developmental stages are included into the analyses, such as larvae, nymphs, or similar immature stages. The inclusion of such developmental stages into analyses is not restricted to insects living today, but is possible with fossil representatives as well. In this way, evolutionary changes in the individual development (ontogeny) of different insects can be investigated (palaeo-evo-devo). Especially in amber, many earlier developmental stages in very good preservation can be found which allow such investigations. With this material, different aspects of fossil developmental biology can be studied in the frame of this project, e.g., when was the oldest appearance of certain developmental stages, or which types of immatures were preserved in amber that are now extinct, possessing a mixture of morphological characters of known modern types, or possessing a morphology completely unknown from modern types. For these investigations, developmental stages of insects in amber of different ages are available, i.e. from 100 million-year-old, 40–50 million-year-old and about 25 million-year-old amber, as well as modern representatives from diverse museum collections. The material is documented under high resolution with different light microscopic methods as well as micro-computed tomography (microCT) to retrieve all morphological details, detect unusual character combinations, and identify possible developmental sequences. As it will in most cases not be possible to identify that different developmental stages belong to the same species, a relaxed taxonomic frame will be used; in this way, developmental sequences within larger phylogenetic groups can be identified. By comparing data from different geological ages, evolutionary changes of the developmental pattern can be detected. These can be the basis for a better understanding of diversification and extinction events in insects.