Konrad Lorenz Institut für Vergleichende Verhaltensforschung, Osterreischische Academie der Wissenschaften, Wien, Austria.
Proc Biol Sci. 2010 Jul 7;277(1690):2083-8. doi: 10.1098/rspb.2010.0109. Epub 2010 Mar 10.
Parent-offspring conflict predicts that offspring should demand a greater parental investment than is optimal for their parents to deliver. This would escalate the level of offspring demand ad infinitum, but most of the models on the evolution of parent-offspring communication predict that begging must be costly, such costs limiting the escalation and defining an optimal level of begging. However, empirical evidence on this issue is mixed. A potential begging cost that remains to be accurately explored is a decrease in immunocompetence for offspring begging fiercely. This study experimentally analyses this cost in house sparrow (Passer domesticus) nestlings. A group of nestlings was forced to beg fiercely for a prolonged time while a control group begged at low levels, both groups receiving the same quantity of food. At the same time, the nestling response to an antigen (phytohaemagglutinin) was measured. Nestlings forced to beg fiercely showed a reduction in immunocompetence with respect to control chicks, but the two groups showed no difference in growth rate. The largest and the smallest nestlings in each brood showed a similar response to the treatment. These results strongly suggest a trade-off between begging and immunocompetence in this species. This trade-off may be a consequence either of resources from the immune system being reallocated to begging behaviour, or of adaptive immunosuppression in order to avoid oxidative stress. Steroid hormones are proposed as mediators of such a trade-off.
亲代-后代冲突预测，后代应该要求比父母最优分配给他们的更多的亲代投资。这将使后代的需求无限升级，但大多数关于亲代-后代交流进化的模型预测，乞求是有代价的，这种代价限制了升级，并定义了最佳的乞降水平。然而，关于这个问题的经验证据是混杂的。一个仍然需要准确探索的潜在乞降代价是，强烈乞降的后代的免疫能力下降。本研究通过实验分析了家麻雀（Passer domesticus）雏鸟中的这种代价。一组雏鸟被迫长时间强烈乞降，而对照组则以低水平乞降，两组都接受相同数量的食物。同时，测量了雏鸟对抗原（植物血凝素）的反应。与对照组小鸡相比，被迫强烈乞降的雏鸟的免疫能力下降，但两组在生长速度上没有差异。每个窝中最大和最小的雏鸟对这种处理表现出相似的反应。这些结果强烈表明，在这个物种中，乞求和免疫能力之间存在权衡。这种权衡可能是由于免疫系统的资源被重新分配到乞降行为中，或者是为了避免氧化应激而进行的适应性免疫抑制的结果。类固醇激素被提出作为这种权衡的中介。
