Vickery W L, Poulin R
Département des Sciences Biologiques, Université du Québec à Montréal, Canada.
Int J Parasitol. 1998 May;28(5):727-37. doi: 10.1016/s0020-7519(98)00036-8.
We determined what evolutionary processes influence the likelihood of detecting an effect of host ecological characteristics on the richness of parasite communities in comparative analyses among related host species. We used a mathematical model to generate phylogenies of hosts in which parasite communities varied over evolutionary time as parasite species were either gained or lost during host speciation events. Gain or loss of parasites were stochastic and could either be strongly, moderately, weakly, or not, affected by host ecological characteristics. The model was evaluated over this range of effects of host ecology, and for various mean probabilities of parasite gain and loss and various rates of change in host ecological characteristics at speciation events. Our results suggest that phylogenetic effects (the passing of parasite species from mother to daughter host species) are likely to obscure ecological effects (the effect of host body size, diet, habitat, lifespan, etc.) except when the effects of host ecology are strong, and the probabilities of gain or loss of parasites are high, or host ecological characteristics change markedly at speciation events. This outcome was not influenced by the shape of the phylogenetic tree used in the simulations. Sensitivity analysis of our model also shows this result to be robust to a wide range of assumptions and parameter values. Thus, because the composition of parasite communities tends to reflect their ancestry, the effect of host ecology will often be very difficult to detect.
我们确定了在对相关宿主物种进行比较分析时，哪些进化过程会影响检测宿主生态特征对寄生虫群落丰富度产生影响的可能性。我们使用一个数学模型来生成宿主的系统发育树，其中寄生虫群落会随着进化时间而变化，因为在宿主物种形成事件中寄生虫物种会有增减。寄生虫的增减是随机的，并且可能受到宿主生态特征的强烈、中等、微弱或无影响。该模型在宿主生态的这一影响范围内进行评估，同时针对寄生虫增减的各种平均概率以及物种形成事件中宿主生态特征的各种变化率进行评估。我们的结果表明，系统发育效应（寄生虫物种从母宿主物种传递到子宿主物种）可能会掩盖生态效应（宿主体型、饮食、栖息地、寿命等的影响），除非宿主生态效应很强，寄生虫增减的概率很高，或者在物种形成事件中宿主生态特征发生显著变化。这一结果不受模拟中使用的系统发育树形状的影响。对我们模型的敏感性分析还表明，这一结果对于广泛的假设和参数值都具有稳健性。因此，由于寄生虫群落的组成往往反映其祖先情况，宿主生态的影响通常很难检测到。
