VIRULENCE NOT ONLY COSTS BUT ALSO BENEFITS THE TRANSMISSION OF A FUNGAL VIRUS
Version of Record online: 22 APR 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 66, Issue 8, pages 2540–2550, August 2012
How to Cite
Bryner, S. F. and Rigling, D. (2012), VIRULENCE NOT ONLY COSTS BUT ALSO BENEFITS THE TRANSMISSION OF A FUNGAL VIRUS. Evolution, 66: 2540–2550. doi: 10.1111/j.1558-5646.2012.01637.x
- Issue online: 26 JUL 2012
- Version of Record online: 22 APR 2012
- Accepted manuscript online: 30 MAR 2012 04:26AM EST
- Received December 2, 2011 , Accepted March 3, 2012
- Cryphonectria hypovirus;
- Cryphonectria parasitica;
- host–parasite interaction;
- transmission rate;
- virulence evolution
Current theory suggests that cost–benefit relationships govern the evolution of parasite virulence. The cost of virulence is expected to be high for fungal viruses, which are obligate parasites and completely dependent on their hosts. The majority of fungal viruses infect their hosts without any apparent symptoms. Cryphonectria hypovirus 1 (CHV-1), in contrast, is virulent and debilitates its host, Cryphonectria parasitica. However, the virulence of CHV-1 is associated with high costs for virus transmission, such as an attenuated fungal growth and reduced production of the fungal spores spreading the virus. In this study, we tested the hypothesis that virulence may not only have costs but also benefits for transmitting CHV-1 across vegetative incompatibility barriers between fungi. We investigated viruses with low, medium, and high virulence, and determined their transmission rate per host-to-host contact (transmissibility). The average transmission rate across all combinations tested was 53% for the most virulent virus, 37% for the virus with intermediate virulence, and 20% for the virus with lowest virulence. These results showed that increased virulence was strongly correlated with increased transmissibility, potentially counterbalancing virulence costs. This association of virulence and transmissibility may explain why CHV-1 spread widely and evolved higher virulence than most other fungal viruses.