Evolution of virulence: triggering host inflammation allows invading pathogens to exclude competitors.
Virulence is generally considered to benefit parasites by enhancing resource-transfer from host to pathogen. Here, we offer an alternative framework where virulent immune-provoking behaviours and enhanced immune resistance are joint tactics of invading pathogens to eliminate resident competitors (transferring resources from resident to invading pathogen). The pathogen wins by creating a novel immunological challenge to which it is already adapted. We analyse a general ecological model of 'proactive invasion' where invaders not adapted to a local environment can succeed by changing it to one where they are better adapted than residents. However, the two-trait nature of the 'proactive' strategy (provocation of, and adaptation to environmental change) presents an evolutionary conundrum, as neither trait alone is favoured in a homogenous host population. We show that this conundrum can be resolved by allowing for host heterogeneity. We relate our model to emerging empirical findings on immunological mediation of parasite competition.
Brown
Sam P
SP
Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA. sam.brown@cantab.net
Le Chat
Ludovic
L
Taddei
François
F
D000818:Animals; D005075:Biological Evolution; D006790:Host-Parasite Interactions / Q000276:immunology*; D007249:Inflammation / Q000469:parasitology*; D008954:Models, Biological; D010271:Parasites / Q000276:immunology / Q000472:pathogenicity*; D014774:Virulence