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

无论是在陆地生态系统还是在淡水生态系统中，昆虫都是当今占主导地位的动物群体之一。然而，不同的研究表明，昆虫多样性目前正处于濒危状态。为了加强我们对导致多样性丧失的过程的理解，过去生态系统中类似的过程可以提供重要的信息。这些信息可以从化石记录中检索到。这个项目的重点是保存在琥珀中的昆虫。琥珀可以将形态结构保存到非常详细的程度，与今天的昆虫相当。昆虫科的多样性不仅表现在物种丰富度上，而且表现在形态多样性上。这一点非常明显，不仅是成虫，还包括早期的发育阶段，如幼虫、若虫或类似的未成熟阶段。把这样的发育阶段纳入分析，不仅局限于今天生活的昆虫，对化石代表也是可能的。通过这种方式，可以研究不同昆虫个体发育（个体发育）的进化变化（古进化-进化）。特别是在琥珀中，可以发现许多保存得很好的早期发育阶段，这使得研究成为可能。有了这些材料，化石发育生物学的不同方面可以在这个项目的框架内进行研究，例如，某些发育阶段最古老的外观是什么时候，或者哪些类型的未成熟生物被保存在琥珀中，现在已经灭绝，具有已知现代类型的混合形态特征，或者具有现代类型完全未知的形态。在这些调查中，昆虫在不同年龄的琥珀中的发育阶段是可用的，即1亿年前，4000 - 5000万年前和大约2500万年前的琥珀，以及来自不同博物馆收藏的现代代表。该材料在高分辨率下用不同的光显微方法以及微计算机断层扫描（microCT）进行记录，以检索所有形态学细节，检测异常的字符组合，并确定可能的发育序列。由于在大多数情况下不可能确定不同的发育阶段属于同一物种，因此将使用一个宽松的分类框架；通过这种方式，可以确定较大系统发育群中的发育序列。通过对比不同地质时代的资料，可以发现发育模式的演化变化。这些可以成为更好地理解昆虫多样化和灭绝事件的基础。

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.