Houston Alasdair I, McNamara John M, Barta Zoltán, Klasing Kirk C
School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
Proc Biol Sci. 2007 Nov 22;274(1627):2835-42. doi: 10.1098/rspb.2007.0934.
In order to avoid both starvation and disease, animals must allocate resources between energy reserves and immune defence. We investigate the optimal allocation. We find that animals with low reserves choose to allocate less to defence than animals with higher reserves because when reserves are low it is more important to increase reserves to reduce the risk of starvation in the future. In general, investment in immune defence increases monotonically with energy reserves. An exception is when the animal can reduce its probability of death from disease by reducing its foraging rate. In this case, allocation to immune defence can peak at intermediate reserves. When food changes over time, the optimal response depends on the frequency of changes. If the environment is relatively stable, animals forage most intensively when the food is scarce and invest more in immune defence when the food is abundant than when it is scarce. If the environment changes quickly, animals forage at low intensity when the food is scarce, but at high intensity when the food is abundant. As the rate of environmental change increases, immune defence becomes less dependent on food availability. We show that the strength of selection on reserve-dependent immune defence depends on how foraging intensity and immune defence determine the probability of death from disease.
为了避免饥饿和疾病，动物必须在能量储备和免疫防御之间分配资源。我们研究了最优分配情况。我们发现，储备较低的动物比储备较高的动物选择分配给防御的资源更少，因为当储备较低时，增加储备以降低未来饥饿风险更为重要。一般来说，对免疫防御的投入会随着能量储备单调增加。一个例外情况是，当动物可以通过降低觅食率来降低死于疾病的概率时。在这种情况下，对免疫防御的分配在中等储备水平时可能达到峰值。当食物随时间变化时，最优反应取决于变化的频率。如果环境相对稳定，动物在食物稀缺时觅食强度最大，在食物丰富时比在稀缺时对免疫防御投入更多。如果环境变化迅速，动物在食物稀缺时觅食强度低，但在食物丰富时觅食强度高。随着环境变化速率的增加，免疫防御对食物可利用性的依赖程度降低。我们表明，对依赖储备的免疫防御的选择强度取决于觅食强度和免疫防御如何决定死于疾病的概率。
