The reproductive and mating strategies of the twisted-winged parasites (Insecta: Strepsiptera): novel insights in the reproductive biology of an enigmatic insect order

• Applicants: Professor Dr. Rolf Georg Beutel; Professor Dr. Oliver Niehuis; Privatdozent Dr. Hans Pohl
• Subject Area: Evolution, Anthropology ; Systematics and Morphology (Zoology)
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 436226643

The interaction between males and females during copulation rarely proceeds in perfect harmony, and sexual aggression is widespread in the animal kingdom. A particularly unusual and bizarre form of sexual aggression is traumatic mating, during which the genitals or other body parts of a sexual partner are injured. Traumatic mating is widespread and a multifaceted phenomenon and it evolved in various evolutionary lineages (e.g., amphibians, snails, annelids, nematodes, and arthropods). Traumatic mating can manifest itself in different ways, such as traumatic penetration (injury of the female) or traumatic insemination (hypodermal injection of sperm). Traumatic insemination occurs in several insect lineages, in particular in bed bugs and the twisted-winged parasites (Strepsiptera), which serve as text book examples for major insect groups exhibiting this peculiar copulation mode. Whether traumatic insemination indeed represents the general mating strategy of Strepsiptera is unclear, however. In fact, it has recently been postulated that in Strepsiptera traumatic insemination is limited to species of the species-poor family Mengenillidae, whose females are free-living. Those strepsipterans whose females are permanent endoparasites (Stylopidia) are assumed to have switched back to non-traumatic mating. Finally, it has been argued that Strepsiptera females mate only with a single male (monandry) and that there is no co-evolutionary arms race between the sexes in the group. Our research project aims to study the poorly known reproductive biology of the enigmatic twisted-winged parasites for the first time comprehensively and in unprecedented detail. We will apply an interdisciplinary approach that comprises a wide array of modern research methods from various disciplines (i.e., comparative anatomy and functional morphology, molecular biology, biomechanics). This study is required as the above statements on the reproductive biology of Strepsiptera are largely speculative and likely premature. For example, we have reason to assume that traumatic insemination occurs in all lineages of Strepsiptera, not only in Mengenillidae, and that this insect order thus legitimately deserves to be mentioned in text books as example for a major group of organisms that makes general use of this mode of copulation. We furthermore assume that Strepsiptera females of different subgroups can get fertilized by multiple males (polyandry), and that females are morphological adapted to traumatic insemination via evolution of tolerance traits. The results of our research project will thus not only reveal novel insights into the elusive reproductive biology of species of Strepsiptera, but will also be of major interest to evolutionary biologists who study sexual conflict and co-evolution.

• DFG Programme: Research Grants