Konrad Lorenz Institute of Ethology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Vienna, Austria.
PLoS One. 2013 Apr 29;8(4):e62541. doi: 10.1371/journal.pone.0062541. Print 2013.
In many socially monogamous species, both sexes seek copulation outside the pair bond in order to increase their reproductive success. In response, males adopt counter-strategies to combat the risk of losing paternity. However, no study so far has tried to experimentally prove the function of behaviour for paternity assurance. Introducing a potential extra-pair partner during the female fertile period provides a standardised method to examine how pair members respond immediately (e.g. increase mate guarding or copulation frequency) or long term (e.g. later parental investment and paternity uncertainty). In this study on a socially monogamous passerine species, we experimentally confronted pairs of reed warblers with a conspecific male (caged male simulating an intruder) during egg-laying. Our results revealed that occurrence of an intruder during that period triggered aggression against the intruder, depending on the presence of the female. The male territory owner also attacked the female partner to drive her away from the intruder. Thus territory defence in reed warblers also serves to protect paternity. The increase in paternity uncertainty did not affect later paternal investment. Paternal investment was also independent of the actual paternity losses. In females, the experiment elicited both, immediate and long-term responses. E.g. female copulation solicitations during the intruder experiment were only observed for females which later turned out to have extra-pair chicks in their nest. In relation to long term response females faced with an intruder invested later less in offspring feeding, and had less extra-pair chicks in their nests. Extra-pair paternity also seems to be affected by female quality (body size). In conclusion female reed warblers seem to seek extra-pair fertilizations but we could demonstrate that males adopt paternity assurance tactics which seems to efficiently help them to reduce paternity uncertainty.
在许多社会一夫一妻制的物种中，雌雄两性都为了增加繁殖成功率而寻求与配偶以外的个体交配。作为回应，雄性会采取对策来对抗失去亲权的风险。然而，迄今为止，没有研究试图通过实验证明行为在确保亲权方面的作用。在雌性的繁殖期引入一个潜在的婚外伴侣提供了一种标准化的方法来检验配偶双方如何立即（例如增加配偶守护或交配频率）或长期（例如后期亲代投资和父权不确定性）做出反应。在这项对一种社会一夫一妻制雀形目鸟类的研究中，我们在产卵期间通过实验向芦苇莺的配对个体引入了一只同种雄性（关在笼子里的雄性模拟入侵者）。我们的研究结果表明，在这段时间内，入侵者的出现会引发针对入侵者的攻击，这取决于雌性的存在。雄性领地所有者也会攻击雌性伴侣，将其驱赶离入侵者。因此，芦苇莺的领地防御也有助于保护亲权。父权不确定性的增加并不会影响后期的亲代投资。亲代投资也与实际的亲权损失无关。在雌性中，实验引发了即时和长期的反应。例如，只有那些后来在巢中出现婚外雏鸟的雌性，才会在入侵者实验中发出求偶行为。就长期反应而言，面临入侵者的雌性后期对后代的喂养投入较少，其巢中婚外雏鸟也较少。婚外受精的父权似乎也受到雌性质量（体型）的影响。总之，雌性芦苇莺似乎在寻求婚外受精，但我们可以证明，雄性会采取亲权保障策略，这似乎有效地帮助它们降低父权不确定性。
