Insects and their pathogens and parasites are excellent model systems to test fundamental theory and concepts in host-parasite ecology and evolution.
Indian Meal Moth (Plodia interpunctella) and its granulosis virus
Photograph by Mvuijlst
Our main laboratory model is the Indian meal moth Plodia interpunctella and its granulosis virus (PiGV). The system is easy to maintain in the laboratory allowing large-scale experiments to be carried out on insects from a large outbred stock population. We can maintain populations of the host with the virus over long periods allowing experimental evolution to occur and the effects on population dynamics of the parasite to be determined. This has been used principally to examine the role of spatial structure in host-parasite interactions and the evolution of host defense.
We have shown that the virus had lower infectivity in more viscose populations (as predicted by theory):
- Boots, M., & Mealor, M. (2007). Local interactions select for lower pathogen infectivity. Science, 315(5816), 1284–1286 https://doi.org/10.1126/science.1137126
The virus had a more significant effect on host population dynamics in the more viscose populations:
We have found that spatial clustering decreases cannibalism, a common behavior in Plodia interpunctella larvae, which supports theoretical predictions:
- Boots, M., Childs, D., Crossmore, J., Tidbury, H., & Rudolf, V. (2021). Experimental evidence that local interactions select against selfish behaviour. Ecology Letters, 24(6), 1187–1192 https://doi.org/10.1111/ele.13734
- Rudolf, V. H. W., Kamo, M., & Boots, M. (2010). Cannibals in space: The coevolution of cannibalism and dispersal in spatially structured populations. American Naturalist, 175(5), 513–524 https://doi.org/10.1086/651616
There also tends to be a trade-off between the level of host resistance with life history traits in this system:
- Mealor, M. A., & Boots, M. (2006). An indirect approach to imply trade-off shapes: population level patterns in resistance suggest a decreasingly costly resistance mechanism in a model insect system. Journal of Evolutionary Biology, 19(2), 326–330 https://doi.org/10.1111/j.1420-9101.2005.01031.x
- Bartlett, L. J., Wilfert, L., & Boots, M. (2018). A genotypic trade‐off between constitutive resistance to viral infection and host growth rate. Evolution, 72(12), 2749–2757 https://doi.org/10.1111/evo.13623
But it’s complicated:
- Bartlett, L. J., Visher, E., Haro, Y., Roberts, K. E., & Boots, M. (2020). The target of selection matters: An established resistance—development‐time negative genetic trade‐off is not found when selecting on development time. Journal of Evolutionary Biology, 33(8), 1109–1119 https://doi.org/10.1111/jeb.13639
- Boots, M. (2011). The Evolution of Resistance to a Parasite Is Determined by Resources. The American Naturalist, 178(2), 214–220 https://doi.org/10.1086/660833
- Roberts, K. E., Meaden, S., Sharpe, S., Kay, S., Doyle, T., Wilson, D., Bartlett, L. J., Paterson, S., & Boots, M. (2020). Resource quality determines the evolution of resistance and its genetic basis. Molecular Ecology, 29(21), 4128–4142 https://doi.org/10.1111/mec.15621
- Su, M., & Boots, M. (2017). The impact of resource quality on the evolution of virulence in spatially heterogeneous environments. Journal of Theoretical Biology, 416(July 2016), 1–7 https://doi.org/10.1016/j.jtbi.2016.12.017
- Visher, E., Uricchio, L., Bartlett, L., DeNamur, N., Yarcan, A., Alhassani, D., & Boots, M. (2022). The evolution of host specialization in an insect pathogen. Evolution, 76(10), 2375–2388 https://doi.org/10.1111/evo.14594
The Honeybee (Apis mellifera) and deformed wing virus
The honeybee is parasitized by the varroa mite, a vector for many viruses. We are using this system as a model to understand the evolution of parasite virulence in vectorborne disease. As well as the general importance of this work, there is now real concern that honeybee declines may result from infection with viruses.
We have recently shown that the spread of DWV is manmade:
Boots Lab - UC Berkeley 