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

昆虫门是当今在陆地和淡水生态系统中占主导地位的动物群体之一。然而，不同的研究表明，昆虫的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，过去生态系统中的类似过程可以提供关键信息。这样的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。琥珀可以非常详细地保存形态结构，可以与今天生活的昆虫相媲美。然而，昆虫门的多样性不仅表现在它的物种丰富度上，而且还表现在它的形态多样性上。当分析不仅包括成虫形态，而且包括早期发育阶段时，这一点变得非常明显，例如幼虫、若虫或类似的未成熟阶段。将这些发育阶段纳入分析并不局限于今天生活的昆虫，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Evo-Devo)。特别是在琥珀中，可以找到保存非常完好的许多早期发育阶段，这使得这种调查成为可能。利用这种材料，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出现时间，或者哪些类型的未成熟化石被保存在现在已经灭绝的琥珀中，具有已知的现代类型的形态特征的混合，或者具有现代类型完全未知的形态。在这些研究中，可以获得不同年龄的琥珀中昆虫的发育阶段，即从1亿年前、40-5000万年前和大约2500万年前的琥珀，以及来自不同博物馆藏品的现代代表。这些材料在高分辨率下被记录下来，使用不同的光学显微镜方法以及微型计算机断层扫描(MicroCT)来检索所有形态细节，检测不寻常的特征组合，并识别可能的发育序列。由于在大多数情况下无法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；这样，就可以确定较大的系统发育类群中的发育序列。通过对比不同地质时代的资料，可以检测到发育模式的演化变化。这些可能是更好地理解昆虫多样性和灭绝事件的基础。

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.