Palacios Maria G, Martin Thomas E
Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT, 59812, USA.
Oecologia. 2006 Jan;146(4):505-12. doi: 10.1007/s00442-005-0220-3. Epub 2005 Oct 11.
Developmental periods are integral components of life history strategies that can have important fitness consequences and vary enormously among organisms. However, the selection pressures and mechanisms causing variation in length of developmental periods are poorly understood. Particularly puzzling are prolonged developmental periods, because their selective advantage is unclear. Here we tested the hypotheses that immune function is stronger in species that are attacked at a higher rate by parasites and that prolonged embryonic development allows the development of this stronger immune system. Through a comparative field study among 12 coexisting passerine bird species, we show that species with higher blood parasite prevalence mounted stronger cellular immune responses than species with lower prevalence. These results provide support for the hypothesis that species facing greater selection pressure from parasites invest more in immune function. However, species with longer incubation periods mounted weaker cellular immune responses than species with shorter periods. Therefore, cellular immune responses do not support the hypothesis that longer development time enhances immunocompentence. Future studies should assess other components of the immune system and test alternative causes of variation in incubation periods among bird species.
发育时期是生活史策略的重要组成部分，可能会产生重要的适合度后果，并且在不同生物之间差异巨大。然而，导致发育时期长度变化的选择压力和机制却鲜为人知。特别令人困惑的是延长的发育时期，因为其选择优势尚不清楚。在这里，我们检验了以下假设：在受到寄生虫攻击率较高的物种中免疫功能更强，并且延长的胚胎发育能够使这种更强的免疫系统得以发育。通过对12种共存的雀形目鸟类进行的一项比较性野外研究，我们发现血液寄生虫患病率较高的物种比患病率较低的物种表现出更强的细胞免疫反应。这些结果支持了以下假设：面临来自寄生虫更大选择压力的物种会在免疫功能上投入更多。然而，孵化期较长的物种比孵化期较短的物种表现出较弱的细胞免疫反应。因此，细胞免疫反应并不支持延长发育时间会增强免疫能力这一假设。未来的研究应该评估免疫系统的其他组成部分，并测试鸟类物种孵化期变化的其他原因。
