Masquerade: critical testing of the ecology of disguise.

众所周知，许多物种的外表受到捕食者对个体检测能力降低的选择的影响(一种被称为隐蔽或伪装的机制)。然而，一些物种通过一种完全不同的机制来强烈选择它们的外部外观，我们称之为伪装。然而，使用密码时，对环境中个体的检测会减少；使用伪装时，捕食者会检测到潜在猎物的存在，但随后会错误地将其识别为不吸引人的食物。因此，使用密码，捕食者在没有意识到的情况下靠近猎物；而使用伪装，捕食者意识到它正在靠近一个实体，但错误地将该实体归类为不感兴趣的东西。伪装的例子包括看起来像树枝的毛虫、看起来像鸟粪的蜘蛛、看起来像枯叶的鱼和看起来像兰花的螳螂。尽管这样的例子相对来说是众所周知的，但对伪装的科学研究一直很少；这与历史上和最近关于密码的强劲研究活动形成了鲜明对比。因此，这个项目将是对化妆舞会生态的第一次实质性调查。具体地说，我们将回答这一机制的一些基本方面，这些方面以前从未探索过。首先，虽然隐蔽和伪装之间的区别在概念上是明确的，而且似乎很明显，例如模仿树枝的毛虫与它们寄主树上的树枝之间的视觉匹配水平是由对伪装的选择驱动的，但目前还没有明确的经验证明伪装对健康的好处。因此，我们将专注于模仿树枝的毛毛虫来回答以下问题：一个物种能否被证明特别受益于伪装而不是神秘？物种很可能同时受益于密码和伪装，因此我们将使用相同的系统来探索是否可以在没有密码的情况下进行伪装；以及伪装和密码的联合作用可以在多大程度上提高存活率。当然，如果你仔细观察一只模仿树枝的毛毛虫(或者它会移动，有时它必须移动才能采集食物)，那么很明显，它是一种毛虫，而不是树枝。因此，如果捕食者通过经验学习识破伪装，伪装可能会变得不那么有效。因此，我们将探索，如果捕食者最近有经验表明伪装物种出现在当地并且是可口的，伪装是否仍然有效；以及有效性是否受到伪装物种的局部密度和他们伪装成的东西的密度的影响。正如前面所暗示的，伪装需要采用无生命物体的外观；然而，对于许多物种来说，它们自己的觅食需要运动。这一冲突的解决方案似乎是，当视觉捕食者在白天盛行时，伪装者会避免移动，只有在晚上才会移动；这一假设也将通过文献调查和有目的的设计实验来验证。看来，许多物种只有在年轻和较小的时候才会采用伪装；当它们年龄较大和较大时，才会切换到其他外观形式(主要是警示颜色)。同样，通过调查现有的跨物种比较文献和有目的的设计实验，我们将试图找出这种通常是戏剧性的外表变化的原因。

It is well known that the external appearance of many species is influenced by selection for reduced ability of predators to detect individuals (a mechanism called crypsis or camouflage). However, some species have their external appearance intensely selected through an entirely different mechanism, which we call masquerade. Whereas with crypsis, detection of the individual in the environment is reduced; with masquerade the predator detects the existence of the potential prey but then misidentifies it as something unattractive to eat. Thus with crypsis, the predator passes close to the prey without realising it; whereas with masquerade the predator realises that it is passing close to an entity but mistakenly classifies that entity as something uninteresting. Examples of masquerade include caterpillars the look like twigs, spiders that look like bird droppings, fish that look like dead leaves and mantids that look like orchids. Although such examples are relatively well known, there has been a lack of scientific enquiry into masquerade; in contrast to historical and recent strong research activity on crypsis. Hence, this project will represent the first substantial investigation of the ecology of masquerade. Specifically, we will provide answers to some fundamental aspects of this mechanism that have never been explored previously. Firstly, although the difference between crypsis and masquerade is clear conceptually, and it seems obvious that the level of visual matching between say twig-mimicking caterpillars and the twigs on their host tree is driven by selection for masquerade, there is currently no unequivocal empirical demonstration of the fitness benefit of masquerade. Hence we will focus on twig-mimicking caterpillars to answer the following question: can a species ever be demonstrated to benefit specifically from masquerade rather than crypsis? It is likely that species benefit through both crypsis and masquerade so we will use the same system to explore whether masquerade can occur in the absence of crypsis; and how much can survival be increased by the joint action of masquerade and crypsis. Of course, if you look closely at a twig-mimicking caterpillar (or it moves, as it must do sometimes to gather food) then it becomes clear that it is a caterpillar and not a twig. Thus masquerade may become less effective if predators learn through experience to see through the disguise. We will thus explore whether masquerade can still be effective if predators have recent experience that the masquerading species occurs locally and is palatable; and if effectiveness is influenced by the local density of the masquerading species and the density of things that they are masquerading as. As previously hinted, masquerade involves adopting the appearance of inanimate objects; yet for many species movement is required for their own foraging. It seems likely that the resolution of this conflict is that masqueraders avoid movement when visual predators are prevalent by day and move to forage only at night; this hypothesis too will be tested both by literature survey and by purpose designed experiments. It would appear that many species adopt masquerade only when they are young and small; switching to other appearance forms (principally warning coloration) when older and larger. Again by surveying available literature for cross-species comparison and through purposed designed experiments we will attempt to identify the reasons for this often-dramatic change in appearance.