1 Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University , Haikou 571158 , People's Republic of China.
2 Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay , F-91405 Orsay Cedex , France.
Philos Trans R Soc Lond B Biol Sci. 2019 Apr 1;374(1769):20180200. doi: 10.1098/rstb.2018.0200.
Before complex nests evolved, birds laid eggs on the ground, and egg retrieval evolved as an adaptation against accidental displacement of eggs outside the nest. Therefore, egg retrieval is an ancient, and likely ancestral, widespread behaviour in birds. However, it has received little attention in studies of avian brood parasitism, perhaps because most parasitism occurs in species with complex nests, a context in which egg retrieval seems irrelevant. However, for cavity-nesting hosts of avian brood parasites, egg retrieval may still play an important role in the coevolutionary interactions between obligate brood parasites and hosts, because egg retrieval can be considered to be antagonistic to egg rejection behaviour in hosts, yet both may involve cognition to recognize eggs. We hypothesized that (1) cavity-nesting hosts should retrieve misplaced eggs from outside the nest cup, (2) brood parasitism has modulated egg retrieval behaviour in cavity-nesting hosts and (3) hosts use the same visual cues for decision-making during egg recognition in both egg retrieval and egg rejection actions. To test these hypotheses, we performed a series of experiments in a cavity-nesting host, the green-backed tit ( Parus monticolus). Foreign eggs with different levels of mimicry were placed within or outside nest cups of hosts to test their responses. We found that host decisions about whether to retrieve or reject an egg both depended on the degree of mimicry. However, hosts sometimes first retrieved poorly mimetic foreign eggs and then rejected them. Alternatively, hosts sometimes failed to retrieve highly mimetic conspecific eggs. We suggest that egg retrieval in hosts is likely to be a result of the interaction between ancient retrieval behaviour and subsequent adaptation against brood parasitism. This article is part of the theme issue 'The coevolutionary biology of brood parasitism: from mechanism to pattern'.
在复杂的鸟巢进化之前，鸟类会在地面上产卵，而卵的取回行为则是一种防止卵意外移出鸟巢的适应行为。因此，卵的取回行为是鸟类中一种古老且可能是祖先的广泛行为。然而，在鸟类育雏寄生研究中，这种行为却很少受到关注，这可能是因为大多数寄生现象发生在具有复杂鸟巢的物种中，而在这种情况下，卵的取回似乎并不相关。然而，对于鸟类育雏寄生的洞穴筑巢宿主来说，卵的取回可能仍然在寄生者和宿主之间的协同进化相互作用中发挥着重要作用，因为卵的取回可以被视为宿主中对卵的排斥行为的拮抗行为，而这两种行为都可能涉及到对卵的识别的认知。我们假设：（1）洞穴筑巢宿主应该从巢杯外取回错位的卵；（2）育雏寄生行为已经在洞穴筑巢宿主中调节了卵的取回行为；（3）宿主在卵识别过程中使用相同的视觉线索来做出决定，无论是在卵的取回还是在卵的排斥行为中。为了检验这些假设，我们在洞穴筑巢的绿背山雀（ Parus monticolus ）宿主中进行了一系列实验。将具有不同程度拟态的外来卵放置在宿主的巢杯内或巢杯外，以测试它们的反应。我们发现，宿主是否取回或拒绝一枚卵的决定既取决于拟态的程度，又取决于拟态的程度。然而，宿主有时会先取回拟态较差的外来卵，然后再拒绝它们。或者，宿主有时会无法取回高度拟态的同种卵。我们认为，宿主中的卵取回行为可能是古老的取回行为与对育雏寄生行为的后续适应之间相互作用的结果。本文是主题为“育雏寄生的协同进化生物学：从机制到模式”的特刊的一部分。
