What is host range?

Project leader


Funding source

Swedish Research Council - Vetenskapsrådet (VR)

Project Details

Start date: 01/01/2016
End date: 31/12/2019
Funding: 3050000 SEK


Interactions between parasites and their hosts are omnipresent, and their ecological importance can hardly be overstated. Understanding how they evolve and how the host range of parasites is determined is therefore a crucial goal in ecology and evolutionary biology. It is also essential for our own species’ health and survival, as illustrated by emergent diseases where the parasite has jumped from distantly related species to humans. Butterfly larvae live parasitically on plants, and the insect-plant field is where much of the theory development in the parasite field has taken place over the last few decades. I have, together with my co-applicants, contributed significantly to this development, suggesting that oscillations in host range over evolutionary time can explain the specific patterns in host range and host shifts that we observe. We recently performed a genomic study of the butterfly Vanessa cardui, which has an extremely broad host repertoire, testing the bold prediction from our oscillation hypothesis that gene expression in larvae reared on different hosts should not cluster according to phylogenetic relatedness of the plants (as predicted from traditional theory) but according to whether the plants are used also by relatives (the ancestral “core” hosts) or only by V. cardui (the novel hosts in the “extended” repertoires). The prediction held, and the fascinating results led us to now propose a project aiming to create conceptual tools of broad generality to parasite-host systems. In order to do this, we want to in detail investigate the model system consisting of V. cardui and related species, and critically test whether our hypotheses hold regarding the fundamental difference between the core and the extended repertoire, as well as our belief that core hosts are associated with specific genetic and phenotypic “modules” of adaptations with some stability over time (explaining re-colonization of ancestral hosts and jumps between them) whereas extended hosts are utilized through a more generalized module. We will attack this question through a powerful combination of different approaches: behavioural studies, neurophysiology, ecological chemistry, genomics and phylogenetics (Bayesian and network analyses of parasite-host associations). We will test predictions such as that butterfly females should search actively for core but not extended hosts; brains of female butterflies should be better adapted at recognizing core than extended hosts; gene expression in larvae of related species feeding on the same ancestral core host should be similar, but this should not be true for independent colonizations of the same host; associations between butterfly species and hosts should be nested within each other in a network analysis if they are the result of past oscillations. Towards the aim of precisely defining modules for host use, we also plan non-targeted metabolomic studies of host plants to clarify the chemical similarities and differences among hosts, and an extension of current Bayesian methods for reconstructing past host ranges so that they can deal with the concept of core hosts that can be lost and re-colonized, forming a potential host range complementing the realized one. By thus developing further the novel concepts of core vs. extended hosts and conserved modules for host use to explain host range and host shifts, we will help provide tools for understanding, anticipating and responding to the changes in parasite-host interactions that are a likely outcome of current environmental change.

Last updated on 2017-28-07 at 08:06