Møller A P, Merino S, Brown C R, Robertson R J
Laboratoire d'Ecologie Evolutive Parasitaire, Centre National de la Recherche Scientifique FRE 2365, Université Pierre et Marie Curie, Bâtiment A, 7ème Etage, 7 Quai St. Bernard, Case 237, F-75252 Paris Cedex 5, France.
Am Nat. 2001 Aug;158(2):136-45. doi: 10.1086/321308.
Sociality is associated with increased risks of parasitism, predation, and social competition, which may interact because social stress can reduce immunity, and parasitized individuals are more likely to fall prey to a predator. A mechanism allowing evolution of sociality in spite of high costs of parasitism is increased investment in antiparasite defenses. Here we show that the impact of parasites on host reproductive success was positively associated with the degree of sociality in the bird family Hirundinidae. However, the cost of parasitism in highly colonial species was countered by high levels of T- and B-cell immune responses. Investment in immune function among colonial species was particularly strong in nestlings, and among social species, this investment was associated with a relatively prolonged period of development, thereby leading to extended exposure to parasites. Thus, highly social species such as certain species of swallows and martins may cope with strong natural selection arising from parasites by heavy investment in immune function at the cost of a long exposure to nest parasites.
社会性与寄生虫感染、被捕食以及社会竞争的风险增加相关，这些风险可能相互作用，因为社会压力会降低免疫力，而被寄生虫感染的个体更容易成为捕食者的猎物。尽管寄生虫感染成本高昂，但一种允许社会性进化的机制是增加对抗寄生虫防御的投入。我们在此表明，寄生虫对宿主繁殖成功率的影响与燕科鸟类的社会性程度呈正相关。然而，高度群居物种中寄生虫感染的成本被高水平的T细胞和B细胞免疫反应所抵消。群居物种对免疫功能的投入在雏鸟中尤为强烈，而在社会性物种中，这种投入与相对较长的发育时期相关，从而导致更长时间暴露于寄生虫。因此，某些燕子和崖燕等高度社会性物种可能通过以长时间暴露于巢寄生虫为代价，大量投入免疫功能来应对寄生虫带来的强大自然选择。
