Adaptive species radiations (i.e. the diversification of species into sister-species flocks by adaptation to different ecological environments in short evolutionary time) have ecosystem effects through altering trophic interactions and “food-web” dynamics. Yet little is known about how radiations affect other interspecific interactions, such as host-parasite associations. This project will allow us to investigate the determinants of diversity and genetic structure of parasites in hosts that have recently diversified.

Lay summary

The Swiss and Scandinavian whitefish (Coregonus lavaretus complex) is a major example of animal radiations with multiple species and divergent populations at different stages of the speciation continuum since last glaciation. This fish model radiation allows us to search for parallel patterns of diversification in parasite species composing the communities infecting this host. In this project we will use a combination of field data, population genomics approaches, and co-phylogenetic analyses, with the ultimate aim of understanding the role of evolutionary and ecological processes at different geographical scales by which host diversity may trigger parasite diversification promoting host specificity. We will assess whether parasite diversity follows the habitat heterogeneity hypothesis. We will quantify genetic differentiation of parasite populations across a diversity of host species over a large geographical scale. We will examine the contribution of parasite and host ecological traits to the congruence of host and parasite phylogeographic structures.

From a social perspective, this research is important to better understand the emergence of new parasitic diseases, the impact of biological invasions, or changes in the distribution of parasites that are related to parasite specificity. Furthermore, whitefish are native salmonids to Europe, commercially important and considered as species vulnerable to climate change by IUCN. Monitoring parasite infection levels can be used as early warning tools for management and conservation purposes.