Morphology, Evolution and Host-Driven Convergence in Ichneumonidae (Hymenoptera, Ichneumonoidea)

Understanding the functional and evolutionary significance of morphology is fundamental to interpreting the tree of life. In recent years, emerging tools have enabled broad-scale analysis of discrete morphological data and facilitated the study of entire phenomes, helping to re-establish morphology as a central component of evolutionary research. These advances allow us not only to examine individual traits in detail but also to compare them across taxa and explore their evolutionary trajectories. This approach is particularly critical when studying hyperdiverse groups that exhibit both high levels of morphological convergence and complex life cycles intricately tied to host use. A prime example is the Ichneumonidae – the most species-rich family of parasitoid wasps – which presents an ideal model for such investigations due to their extraordinary species diversity, broad range of host associations, diverse life history strategies, and repeated convergent adaptations for host exploitation. However, to draw meaningful inferences about phenome evolution, several foundational components are required: (1) characters must be clearly defined and rigorously reviewed, (2) character statements should be supported by a standardized ontology to ensure consistency and comparability, and (3) a robust, preferably time-calibrated phylogeny must be available. While important advances have been made in each of these areas over the years, key limitations remain for Ichneumonidae – particularly in terms of comprehensive character definitions, standardized terminology, and the availability of a robust, time-calibrated phylogeny. My thesis responds to these limitations with the overarching aim of understanding morphology and its role in the evolution of parasitoid wasps. By addressing key knowledge gaps and developing tools that strengthen the morphological foundation for evolutionary research, this work helps establish a more complete framework for broad-scale evolutionary analyses. To achieve this, I integrate diverse morphological systems and analytical approaches. In Chapter 2, I develop a standardized terminology for male genitalia in Ichneumonoidea, aligning legacy terminology with the Hymenoptera Anatomy Ontology to improve clarity and interoperability. In Chapter 3, I investigate ovipositor morphology and describe a novel steering mechanism for host localization, including the discovery of a sclerite fuctionally equivalent to the furcula in Aculeata. In Chapter 4, I examine multi-trait convergent syndromes associated with parasitoids of wood-boring hosts, providing new insights into the repeated evolution of functionally similar morphologies. In Chapter 5, I assess evolutionary rate variation across a time-calibrated phylogeny to test whether major transitions in host use correlate with shifts in the tempo of morphological evolution. This dissertation deepens our understanding of the morphological innovations and constraints shaping Ichneumonidae evolution by uncovering novel traits, standardizing terminology, and linking host use to evolutionary rate shifts—laying the foundation for comparative phenomic research in parasitoid wasps.