Like most biologists, I am absolutely fascinated by biodiversity in all of its forms. From all the facets of individual diversity and species diversity to the variation in species interactions, variety really is the spice of life. How this diversity is shaped by evolution, ecological processes and their eco-evolutionary interactions is a question I am exploring both in the context of host-parasite interactions and in regards to the evolutionary significance of phenotypic plasticity.
Experimentally, I use laboratory based assays to study individual level effects of drivers of contemporary evolution, such as environmental change and parasites, and the mechanisms behind rapid evolution, including phenotypic plasticity (including phenotypic integration plasticity) and non-genetic inheritance. In addition, I use large-scale mesocosm experiments to study the same factors at the population and community level. Such mesocosm experiments allow the simultaneous assessment of evolutionary and ecosystem changes and therefore help to elucidate the ecological feedback to changes in selective pressures. In the most complex experiments, I then follow the the evo-to-eco study up with monitoring the ensuing eco-to-evo effects, thereby closing the eco-evolutionary feedback loop.
Limits to adaptation in a rapidly changing environment
We live in a rapidly changing world and the persistence of many populations and ultimately species will depend on capacity for rapid adaptation to the occuring environmental changes. We are investigating which kind of evolutionary potential drives such rapid adaptation – is it phenotypic plasticity, is it genetic diversity or it is both?
By carrying out a multi-year mesocosm experiment with Daphnia magna populations (see model systems) and their associated planktonic ecosystem, we can monitor population changes as well as ecosystem changes following artificial heatwave events. This will enable us to characterize both evolutionary and eco-evolutionary changes in populations with different initial levels of genetic diversity and phenotypic plasticity.
This research is part of the NERC funded project “Limits to Adaptation” with Stew Plaistow, David Atkinson and Steve Paterson at the University of Liverpool. Our mesocosms are located at the beautiful Ness Botanical Gardens, which are associated with the University.
Combined effects of parasites and environmental change on host evolution
Obviously, each of these three research fields on their own would be enough to find plenty of interesting questions. What I find even more interesting though, is how each of these influence each other in contemporary evolution so I chose the intersection of these fields for my PhD project.
Speciation mechanisms can be driven and shaped by host-parasite interactions through selection pressure from different parasite communities. Host-parasite interactions can differ markedly under varying environmental conditions (e.g. differing temperatures, salinity or rates of disturbance) both in space and in time. And environmental change can both open up opportunity for adaptive radiation and cause species to collapse again in the process of speciation reversal.
Brunner, FS, Eizaguirre, C (2016) Can environmental change affect host-parasite mediated speciation? Zoology, 119(4): 384-394. doi:10.1016/j.zool.2016.04.001
Parasite effects: from genes to ecosystems and back again in eco-evolutionary feedbacks
Thanks to the set-up of 40 artificial ecosystems in the mesocosm garden of Kastanienbaum, we could simultaneously observe responses of three-spined stickleback (see model systems) and the ecosystems around them to combinations of parasitism and artificial eutrophication over the course of a summer.
A first exciting result from this project was our demonstration how parasitism effects can be followed from the molecular level of host responses, across host fitness proxies and host diet up to chemical ecosystem properties.
By following survival of different ecotypes of juveniles in these modified ecosystems, we could eventually show that the ecosystem modifications that have occured due to previous parasite presence alter selection in the next host generation. In other words: parasites have a clear influence on full eco-evolutionary feedback cycles!
More fascinating insights into ecosystem level effects of parasites and their potential to maintain differences between host ecotypes are still to follow, so check back again in a few months or follow me on twitter for updates.
Anaya-Rojas, JM, Best, RJ, Brunner, FS, Eizaguirre, C, Costa Leal, M, Melian, C, Seehausen, O, Matthews, B (2019) Experimental evidence that parasites influence predator driven trophic cascades, Ecology
Brunner, FS, Anaya-Rojas, JM, Matthews, B, Eizaguirre, C (2017) Experimental evidence that parasites drive eco-evolutionary feedbacks Proceedings of the National Academy of Sciences of the United States of America, doi:10.1073/pnas.1619147114
Anaya-Rojas, JM, Brunner, FS, Sommer, N, Seehausen, O, Eizaguirre, C, Matthews, B (2016) The association of feeding behavior with the resistance and tolerance to parasites in recently diverged sticklebacks, Journal of Evolutionary Biology, doi:10.1111/jeb.12934
Ecological immunology of Bombus terrestris
In my master thesis, I could show that the immune responses of the buff-tailed bumblebee to its trypanosome gut parasite Crithidia bombi as revealed by immune gene expression show specific host colony signatures and rely mostly on the upregulation of antimicrobial peptides.
The story doesn’t end there yet – this infection and colony specific upregulation depends on host nutrition. Bumblebees which receive a protein reduced diet fail to upregulate antimicrobial peptides and become overall more similar in their gene expression pattern which has important implications for the ability of their parasite to spread within and among colonies.
Brunner, FS, Schmid-Hempel, P, Barribeau SM (2014) Protein-poor diet reduces host-specific immune gene expression in Bombus terrestris. Proceedings of the Royal Society London-B. 281 doi:10.1098/rspb.2014.0128
Brunner, FS, Schmid-Hempel, P, Barribeau, SM (2013). Immune gene expression in Bombus terrestris: signatures of infection despite strong variation among populations, colonies, and sister workers. PLoS One, 8(7): e68181. doi:10.1371/journal.pone.0068181