Molina-Morales Mercedes, Gabriel Martínez Juan, Martín-Gálvez David, A Dawson Deborah, Rodríguez-Ruiz Juan, Burke Terry, Avilés Jesús M
Departamento de Zoología, Universidad de Granada, Granada, E-18071, Spain; Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
J Anim Ecol. 2013 Mar;82(2):389-98. doi: 10.1111/1365-2656.12022. Epub 2012 Dec 12.
Brood parasites usually reduce their host's breeding success, resulting in strong selection for the evolution of host defences. Intriguingly, some host individuals/populations show no defence against parasitism, which has been explained within the frame of three different evolutionary hypotheses. One of these hypotheses posits that intermediate levels of defence at the population level may result from nonrandom distribution of parasitism among host individuals (i.e. structured parasitism). Empirical evidence for structured brood parasitism is, however, lacking for hosts of European cuckoos due to the absence of long-term studies. Here, we seek to identify the patterns of structured parasitism by studying great spotted cuckoo parasitism on individual magpie hosts over five breeding seasons. We also aim to identify whether individual characteristics of female magpies and/or their territories were related to the status of repeated parasitism. We found that 28·3% of the females in our population consistently escaped from cuckoo parasitism. Only 11·3% of females were always parasitized, and the remaining 60·4% changed their parasitism status. The percentage of females that maintained their status of parasitism (i.e. either parasitized or nonparasitized) between consecutive years varied over the study. Females that never suffered cuckoo parasitism built bigger nests than parasitized females at the beginning of the breeding season and smaller nests than those of parasitized females later in the season. Nonparasitized females also moved little from year to year and preferred areas with different characteristics over the course of the breeding season than parasitized females. Overall, females escaping from cuckoo parasitism reared twice as many chicks per year than those that were parasitized. In conclusion, our study reveals for first time the existence of a structured pattern of cuckoo parasitism based on phenotypic characteristics of individual hosts and of their territories.
巢寄生者通常会降低其宿主的繁殖成功率，从而促使宿主防御机制的进化受到强烈选择。有趣的是，一些宿主个体/种群对寄生行为没有防御反应，对此有三种不同的进化假说进行了解释。其中一种假说认为，种群水平上的中等防御水平可能是由于寄生行为在宿主个体间的非随机分布（即结构化寄生）所致。然而，由于缺乏长期研究，欧洲杜鹃宿主的结构化巢寄生的实证证据尚不充分。在此，我们通过研究大斑杜鹃在五个繁殖季节对喜鹊个体宿主的寄生情况，来确定结构化寄生的模式。我们还旨在确定喜鹊雌性个体及其领地的特征是否与重复寄生的状况有关。我们发现，在我们研究的种群中，28.3%的雌性喜鹊始终未被杜鹃寄生。只有11.3%的雌性喜鹊总是被寄生，其余60.4%的雌性喜鹊的寄生状况发生了变化。在整个研究过程中，连续几年保持寄生状态（即被寄生或未被寄生）的雌性喜鹊的比例有所不同。在繁殖季节开始时，从未遭受杜鹃寄生的雌性喜鹊所筑的巢比被寄生的雌性喜鹊的巢更大，而在繁殖季节后期则比被寄生的雌性喜鹊的巢更小。未被寄生的雌性喜鹊每年的活动范围也较小，并且在繁殖季节中比被寄生的雌性喜鹊更喜欢具有不同特征的区域。总体而言，未被杜鹃寄生的雌性喜鹊每年养育的雏鸟数量是被寄生雌性喜鹊的两倍。总之，我们的研究首次揭示了基于个体宿主及其领地的表型特征而存在的杜鹃寄生结构化模式。
