Dimorphism and life history differentiation in sepsid flies

Submitted by editor on 19 August 2020.Get the paper!

"Sexual size dimorphism is associated with reproductive life history trait differentiation in coexisting sepsid flies" (Blankenhorn et al. 2020)

The study of ecological diversity requires investigation of numerous groups of organisms to reveal the various alternative paths to adaptation and community composition – a strict “model species” approach, as in some other fields of biology (e.g. molecular genetics) is typically not sufficient. Thus, even research groups focusing on particular model species, one of the more famous being the fruit fly Drosophila melanogaster, require background knowledge about the behavior and ecology in the field of their favorite species to better evaluate and interpret what they find in the laboratory. This includes information about other closely related species, which often have similar ecology, because organismal life histories often evolve as syndromes, leading to concerted evolutionary differentiation of key characters that ultimately serve to discern the species of this group.

Together with few other laboratories worldwide, we study the behavior, ecology, micro- and macro-evolution of sepsid black scavenger or dung flies (Diptera: Sepsidae), largely for haphazard historical reasons. These flies are merely distantly related to the better-known fruit flies (Drosophilidae) but share many of their characteristics in terms of laboratory practicalities. Essentially all of the fly species depicted in the phylogeny on the right can be found on a single pasture in Switzerland, raising the question of how these flies are ecologically differentiated. Over several years, we have collected data about these flies’ behavior and reproduction in the laboratory in standardized ways, our own “big data” so to speak. A good way of orchestrating this is to make the necessary collection of such baseline data a side-project of the entire research group (separate from the individual scientific projects) composed of students, technicians and post-docs, additionally involving undergraduate course students to get them interested in nature and our research in particular. We eventually used these data in a study that in the end identified three life history groupings based on the flies’ reproductive traits, mating behavior and sexual body size dimorphism. This differentiation is partly driven by sexual selection ultimately leading to male-biased dimorphism, which however is judged too slight to explain the coexistence of these species on European pastures by way of ecological diversification.

Wolf Blanckenhorn, University of Zurich, Switzerland




Wolf U. Blanckenhorn*, Julian Baur, Juan Pablo Busso, Athene Giesen, Natalia Gourgoulianni, Nicola van Koppenhagen, Jeannine Roy, Martin A. Schäfer, Alexandra Wegmann and Patrick T. Rohner

ORCIDs: U. Blanckenhorn orcid.org/0000-0002-0713-3944 / Martin A. Schäfer orcid.org/0000-0002-0982-1468 / Patrick T. Rohner orcid.org/0000-0002-9840-1050

Correspondence*: Wolf U. Blanckenhorn, Tel.: +41 44 635 47 55; e-mail: wolf [dot] blanckenhorn [at] ieu [dot] uzh [dot] ch

Acknowledgements: This work was supported over the years by the University (Museum) of Zurich and by several grants from the Swiss National Science Foundation, most recently grant no. 31003A_143787.

Author contributions: WUB, MAS and PTR designed the project; all authors contributed to the data collection; PTR and WUB analyzed the data and led the writing of the manuscript.

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