Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, 32611.
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803.
Evolution. 2019 Apr;73(4):636-647. doi: 10.1111/evo.13692. Epub 2019 Feb 14.
The virulence-transmission trade-off hypothesis proposed more than 30 years ago is the cornerstone in the study of host-parasite co-evolution. This hypothesis rests on the premise that virulence is an unavoidable and increasing cost because the parasite uses host resources to replicate. This cost associated with replication ultimately results in a deceleration in transmission rate because increasing within-host replication increases host mortality. Empirical tests of predictions of the hypothesis have found mixed support, which cast doubt about its overall generalizability. To quantitatively address this issue, we conducted a meta-analysis of 29 empirical studies, after reviewing over 6000 published papers, addressing the four core relationships between (1) virulence and recovery rate, (2) within-host replication rate and virulence, (3) within-host replication and transmission rate, and (4) virulence and transmission rate. We found strong support for an increasing relationship between replication and virulence, and replication and transmission. Yet, it is still uncertain if these relationships generally decelerate due to high within-study variability. There was insufficient data to quantitatively test the other two core relationships predicted by the theory. Overall, the results suggest that the current empirical evidence provides partial support for the trade-off hypothesis, but more work remains to be done.
超过 30 年前提出的毒力-传播权衡假说，是宿主-寄生虫协同进化研究的基石。该假说基于这样一个前提，即毒力是不可避免且不断增加的成本，因为寄生虫利用宿主资源进行复制。这种与复制相关的成本最终导致传播率下降，因为增加体内复制会增加宿主死亡率。对该假说预测的实证检验发现，支持结果不一，这对其整体通用性提出了质疑。为了定量解决这个问题，我们在查阅了超过 6000 篇已发表论文后，对 29 项实证研究进行了荟萃分析，以检验（1）毒力与恢复率、（2）体内复制率与毒力、（3）体内复制与传播率、（4）毒力与传播率之间的四个核心关系。我们发现，复制与毒力以及复制与传播率之间存在着很强的正相关关系。然而，由于研究内的变异性较高，这些关系是否普遍减速仍然不确定。没有足够的数据来定量检验该理论预测的其他两个核心关系。总体而言，结果表明，目前的实证证据为权衡假说提供了部分支持，但仍需要做更多的工作。
