Lively Curtis M
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Ecol Lett. 2006 Oct;9(10):1089-95. doi: 10.1111/j.1461-0248.2006.00969.x.
Theoretical work has shown that parasites should evolve intermediate levels of virulence. Less attention has been given to the ecology of virulence. Here I explore population-dynamic models of infection in an annual host. The infection does not kill the host; but it can decrease the number of offspring produced by the host, and the magnitude of this effect depends on host population size. Hence, 'virulence' is density dependent, and is defined here as the difference in birth rates between uninfected and infected hosts, divided by the birth rate of uninfected hosts. The results suggest that infection can be highly virulent at the host's equilibrium density, even though the parasite has no effect on the host's intrinsic birth rate. The results also suggest that parasites may help to stabilize host population dynamics. In general, the impact of infection may be underestimated in natural populations.
理论研究表明，寄生虫应进化出中等水平的毒力。然而，对毒力生态学的关注较少。在此，我探讨一年生宿主中感染的种群动态模型。感染不会杀死宿主，但会减少宿主产生的后代数量，且这种影响的程度取决于宿主种群规模。因此，“毒力”是密度依赖的，在此定义为未感染宿主与感染宿主出生率之差除以未感染宿主的出生率。结果表明，即使寄生虫对宿主的内在出生率没有影响，在宿主的平衡密度下感染仍可能具有高毒力。结果还表明，寄生虫可能有助于稳定宿主种群动态。总体而言，在自然种群中，感染的影响可能被低估了。
