Sexual signals can be evolutionarily stable if they are condition dependent or costly to the signaler. One of these costs may be the trade-off between maintaining the immune system and the elaboration of ornaments. Experimental immune challenges in captivity show a reduction in the expression of sexual signals, but it is not clear whether these detrimental effects are important in nature and, more importantly, whether they have reproductive consequences. We designed a field experiment to challenge the immune system of wild male Carpetan rock lizards, Iberolacerta cyreni, with a bacterial antigen (lipopolysaccharide). The immune challenge decreased relative reflectance of ultraviolet structural and melanin-dependent sexual coloration in the throat and the lateral ocelli, whereas the carotenoid-dependent dorsal green coloration was not affected. Immune activation also decreased proportions of ergosterol and cholesta-5,7-dien-3-ol in femoral secretions. These results support a trade-off between the immune system and both visual and chemical sexual ornaments. Moreover, the reproductive success of males, estimated with DNA microsatellites, depended on the expression of some color and chemical traits. However, the immune challenge did not cause overall differences in reproductive success, although it increased with body size/age in control but not in challenged males. This suggests the use of alternative reproductive strategies (e.g., forced matings) in challenged males, particularly in smaller ones. These males might consider that their survival probabilities are low and increase reproductive effort as a form of terminal investment in spite of their “low-quality” sexual signals and potential survival costs.

中文翻译：

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雄性岩蜥蜴可以补偿影响性信号的免疫挑战的繁殖成本

如果性信号依赖于条件或对信号者来说代价高昂，那么它们在进化上是稳定的。这些成本之一可能是维持免疫系统和装饰品的制作之间的权衡。圈养中的实验性免疫挑战表明性信号的表达减少，但尚不清楚这些有害影响在自然界中是否重要，更重要的是，它们是否具有生殖后果。我们设计了一项田间试验，用细菌抗原（脂多糖）挑战野生雄性 Carpetan 岩蜥蜴 Iberolacerta cyreni 的免疫系统。免疫攻击降低了喉咙和侧眼中紫外线结构和黑色素依赖性性着色的相对反射率，而类胡萝卜素依赖性背绿色不受影响。免疫激活还降低了股骨分泌物中麦角甾醇和 cholesta-5,7-dien-3-ol 的比例。这些结果支持免疫系统与视觉和化学性装饰之间的权衡。此外，用 DNA 微卫星估计雄性的繁殖成功取决于一些颜色和化学特征的表达。然而，免疫攻击并没有导致繁殖成功的总体差异，尽管它随着体型/年龄的控制而增加，但在受攻击的雄性中没有。这表明在受挑战的雄性，尤其是体型较小的雄性中使用替代的生殖策略（例如，强迫交配）。