Nature Communications volume 9, Article number: 3325 (2018)
About 50% of all animal species are considered parasites. The linkage of species diversity to a parasitic lifestyle is especially evident in the insect order Hymenoptera. However, fossil evidence for host–parasitoid interactions is extremely rare, rendering hypotheses on the evolution of parasitism assumptive. Here, using high-throughput synchrotron X-ray microtomography, we examine 1510 phosphatized fly pupae from the Paleogene of France and identify 55 parasitation events by four wasp species, providing morphological and ecological data. All species developed as solitary endoparasitoids inside their hosts and exhibit different morphological adaptations for exploiting the same hosts in one habitat. Our results allow systematic and ecological placement of four distinct endoparasitoids in the Paleogene and highlight the need to investigate ecological data preserved in the fossil record.
Parasitic lifestyles are extremely successful among animals and evolved independently, perhaps hundreds of times. With an estimated 50% of species, parasites comprise a huge proportion of animal life on Earth, and the arms races between parasites and their hosts are considered major driving forces for evolution. In insects, parasitism is especially diverse in the order Hymenoptera, where many wasp species develop as parasitoids on or within an arthropod host, ultimately causing its death. In hymenopteran evolution, multiple transitions between host species, developmental stages and modes of parasitoidism are considered key events linked to enormous adaptive radiations and an estimated 10–20% of all extant insects are parasitoid wasps. Being antagonists of a wide variety of terrestrial arthropods, they have profound ecological and economic impact and many species are used as biological control agents.
Evidence for parasitism in fossils is generally rare, as it requires preserved information of interaction between both partners. As a consequence, the fossil record of parasitoid wasps is nearly exclusively restricted to isolated adults, with few examples of unidentified larvae trapped in amber next to their hosts. Therefore, our understanding of parasitoid evolution is based on the inference that fossil organisms exhibited habits resembling those of their extant relatives. The only record of a putative fossil parasitoid wasp inside its preserved host derives from a thin-section of a mineralized fly pupa from the later middle to late Eocene fissure fillings of the Quercy region in France, approximately 34–40 million years old. The sectioned pupa was thought to comprise an adult braconid wasp, which was only traceable as faint silhouette lacking any diagnostic characters._ Continue reading here or click on thumbnail
cover image Fig.7 (attached to the article)