Abstract
It is becoming increasingly clear that the evolution of infectious disease is influenced by host population structure. Theory predicts that parasites should be more ‘prudent’—less transmissible—in spatially structured host populations. However, here we (i) highlight how low transmission, the phenotype being selected for in this in context, may also be achieved by rapacious host exploitation, if fast host exploitation confers a local, within-host competitive advantage and (ii) test this novel concept in a bacteria–virus system. We found that limited host availability and, to a lesser extent, low relatedness favour faster-killing parasites with reduced transmission. By contrast, high host availability and high relatedness favour slower-killing, more transmissible parasites. Our results suggest high, rather than low, virulence may be selected in spatially structured host–parasite communities where local competition and hence selection for a within-host fitness advantage is high.This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’.
Highlights
Owing to the importance of infectious diseases to human health, agriculture and wildlife populations [1,2,3,4,5,6,7], it is critical that we better understand how ecology shapes the evolution of life histories of infectious organisms
A reason for evolution towards lower transmission rate in structured populations is due to local extinctions of infected hosts: a higher transmission rate is selected until a critical point is reached beyond which any further increase in transmission will cause the local cluster of hosts to be wiped out very rapidly [8]
The above models [9,11,12,13,14,15], and many others [20,21,22,23,24,25], assume that transmission is a positive function of within-host growth rate, which affects pathogen virulence
Summary
Owing to the importance of infectious diseases to human health, agriculture and wildlife populations [1,2,3,4,5,6,7], it is critical that we better understand how ecology shapes the evolution of life histories of infectious organisms. If fast and slow killing have the same consequences for disease transmission, the added advantage of increased within-host competitive ability may, in some contexts, favour faster time to kill in structured host populations.
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