Skorping Arne, Jensen Knut Helge, Mennerat Adèle, Högstedt Göran
Am Nat. 2016 Apr;187(4):540-6. doi: 10.1086/685423. Epub 2016 Feb 23.
We present a life-history model based on the assumptions that juvenile survival follows a negative exponential function and that fecundity gain increases linearly with time to maturity. This model predicts that the optimal fitness is achieved when survival at maturity is 0.368 (e(-1)). Survival at the time of maturity is therefore an invariant. We tested this prediction by using published data from infection experiments with mammalian nematodes, where both the initial number of juveniles colonizing a habitat (host) and the numbers surviving at the time of maturation were known. We found that the mean survival at maturity, both across and within species, was remarkably close to our predicted mean. As a control, we also looked at studies where the parasite species was adapted to a host species other than the one used in the reported experiment. In these experiments the mean survival at maturity differed from what our model predicted. Maturation at a fixed survival probability therefore appears as an adaptive trait evolved in a predictable environment, in this case, a host species. Our result further suggests that measures designed to increase juvenile parasite mortality, such as drugs or vaccines, will select for faster developmental rates.
我们提出了一个生活史模型，该模型基于以下假设：幼体存活率遵循负指数函数，繁殖力增长随成熟时间呈线性增加。该模型预测，当成熟时的存活率为0.368（e⁻¹）时可实现最佳适应性。因此，成熟时的存活率是一个不变量。我们通过使用已发表的关于哺乳动物线虫感染实验的数据来检验这一预测，在这些实验中，定殖于一个栖息地（宿主）的幼体初始数量以及成熟时存活的数量都是已知的。我们发现，无论是跨物种还是物种内，成熟时的平均存活率都非常接近我们预测的平均值。作为对照，我们还研究了寄生虫物种适应于报告实验中所使用宿主物种之外的其他宿主物种的研究。在这些实验中，成熟时的平均存活率与我们模型的预测结果不同。因此，在固定存活概率下成熟似乎是在可预测环境（在这种情况下是宿主物种）中进化出的一种适应性特征。我们的结果进一步表明，旨在提高寄生虫幼体死亡率的措施，如药物或疫苗，将选择更快的发育速度。
