Spatial structure drives the evolution of parasites into host defense systems
- 1Utrecht University
Abstract
Host defense systems in prokaryotes and eukaryotes often appear to be derived from the very parasites they now defend against, yet the evolutionary route for such a transition remains poorly understood. Based on the biology of integrating viruses such as temperate bacteriophages and retroviruses, we develop a multilevel eco-evolutionary framework in which within-host viral replication is treated as a public goods game over a costly, shared replication product. In well-mixed host populations, we predict convergence on a single viral strategy of intermediate replicative investment. However, when we impose spatial structure by restricting host reproduction and virus transmission to local events, the virus population diversifies into two lineages: a horizontally transmitted lineage that parasitises hosts, and a vertically transmitted hyperparasitic lineage that parasitises the horizontally transmitting viruses. The latter "hyperparasite" is a viral cheat that suppresses the replication and propagation of the parasitic virus, thereby acting as a defense system to the hosts. Local interactions concentrate the benefits of this suppression among neighbouring hosts that carry related proviruses, allowing selection on the proviral cheat as a host-level defense. Our results show that evolutionary cheating within parasite populations can drive the evolution of parasites into defense systems in spatially structured host populations.
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BibTeX
@misc{nazir2026spatial,
title = {{Spatial structure drives the evolution of parasites into host defense systems}},
author = {S. A. Nazir and B. Ashby and A. Leeks and B. van Dijk},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.14.759074},
url = {https://www.biorxiv.org/content/10.64898/2026.10.14.759074v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Spatial structure drives the evolution of parasites into host defense systems
AU - S. A. Nazir
AU - B. Ashby
AU - A. Leeks
AU - B. van Dijk
PY - 2026
DA - 2026/10/14
PB - bioRxiv
DO - 10.64898/2026.10.14.759074
UR - https://www.biorxiv.org/content/10.64898/2026.10.14.759074v1
AB - Host defense systems in prokaryotes and eukaryotes often appear to be derived from the very parasites they now defend against, yet the evolutionary route for such a transition remains poorly understood. Based on the biology of integrating viruses such as temperate bacteriophages and retroviruses, we develop a multilevel eco-evolutionary framework in which within-host viral replication is treated as a public goods game over a costly, shared replication product. In well-mixed host populations, we predict convergence on a single viral strategy of intermediate replicative investment. However, when we impose spatial structure by restricting host reproduction and virus transmission to local events, the virus population diversifies into two lineages: a horizontally transmitted lineage that parasitises hosts, and a vertically transmitted hyperparasitic lineage that parasitises the horizontally transmitting viruses. The latter "hyperparasite" is a viral cheat that suppresses the replication and propagation of the parasitic virus, thereby acting as a defense system to the hosts. Local interactions concentrate the benefits of this suppression among neighbouring hosts that carry related proviruses, allowing selection on the proviral cheat as a host-level defense. Our results show that evolutionary cheating within parasite populations can drive the evolution of parasites into defense systems in spatially structured host populations.
ER -