Cornet Stéphane, Biard Clotilde, Moret Yannick
UMR CNRS 5561 Biogéosciences, Equipe Ecologie Evolutive, Université de Bourgogne, 6 Bd Gabriel, 21000 Dijon, France.
Oecologia. 2009 Mar;159(2):257-69. doi: 10.1007/s00442-008-1211-y. Epub 2008 Nov 7.
Despite intensive studies in ecological immunology, few have investigated variation in immune defence among natural populations; in particular, there is a lack of knowledge of the sources of spatial variability in immune defence in the wild. Here we documented variation among twelve populations of the freshwater crustacean Gammarus pulex in the activity of the prophenoloxidase (ProPO) system, which is an important component of invertebrate immunity. We then tested for trade-offs between investment in immune defence and fitness-related traits such as survival and fecundity, as well as for environmental causes of variability (water temperature and conductivity, parasite prevalence). Levels of immune defence differed among populations, with environment partly explaining this population effect, as immune activities were negatively related to water conductivity and acanthocephalan parasite prevalence. There was a strong variation among populations for the maintenance of the ProPO system, while variation in its use was relatively weak. Such a pattern could be partly explained by the relative costs associated with the maintenance and/or the use of the ProPO system. Investment in the ProPO system was negatively correlated to survival, whereas it was positively related to female fecundity and resource storage. However, variation in immunity did not predict resistance to bacterial infection among populations, suggesting that measuring the activity of the ProPO system might not be sufficient to estimate immunocompetence at the population level. These results suggest that investment in immune function is a variable trait, which might be locally optimized as a result of both life history trade-offs and environmental conditions, highlighting the need to combine them in a common framework.
尽管在生态免疫学方面进行了深入研究，但很少有人调查自然种群之间免疫防御的差异；特别是，对于野生免疫防御空间变异性的来源缺乏了解。在这里，我们记录了淡水甲壳类动物蚤状溞的12个种群在酚氧化酶原（ProPO）系统活性方面的差异，该系统是无脊椎动物免疫的重要组成部分。然后，我们测试了免疫防御投资与生存和繁殖力等与适应性相关的性状之间的权衡，以及变异性的环境原因（水温、电导率、寄生虫流行率）。不同种群的免疫防御水平存在差异，环境部分解释了这种种群效应，因为免疫活动与水的电导率和棘头虫寄生虫流行率呈负相关。在维持ProPO系统方面，不同种群之间存在很大差异，而其使用方面的差异相对较小。这种模式可以部分由与维持和/或使用ProPO系统相关的相对成本来解释。对ProPO系统的投资与生存呈负相关，而与雌性繁殖力和资源储存呈正相关。然而，免疫方面的差异并不能预测不同种群对细菌感染的抵抗力，这表明测量ProPO系统的活性可能不足以在种群水平上估计免疫能力。这些结果表明，对免疫功能的投资是一个可变性状，由于生活史权衡和环境条件的综合作用，它可能在局部得到优化，这突出了在一个共同框架中综合考虑它们的必要性。
