Masquerade: critical testing of the ecology of disguise.

众所周知，许多物种的外表是受捕食者发现个体能力降低的选择影响的（这种机制被称为隐蔽或伪装）。然而，有些物种的外表是通过一种完全不同的机制被强烈选择的，我们称之为假面。而在隐型中，个体在环境中的检测减少了；通过伪装，捕食者发现了潜在猎物的存在，但随后将其误认为是没有吸引力的食物。因此，有了隐蔽性，捕食者在没有意识到的情况下接近猎物；而在假面术中，捕食者意识到它正在接近一个实体，但错误地将这个实体归类为无趣的东西。伪装的例子包括看起来像树枝的毛毛虫，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。虽然这样的例子相对来说是众所周知的，但对假面舞会缺乏科学的研究；与历史上和最近对密码学的强烈研究活动形成对比。因此，这个项目将代表对假面舞会生态的第一次实质性调查。具体地说，我们将提供以前从未探索过的这种机制的一些基本方面的答案。首先，尽管在概念上隐蔽和伪装之间的区别是明确的，而且似乎很明显，模仿树枝的毛虫与宿主树上的树枝之间的视觉匹配程度是由伪装的选择驱动的，但目前还没有明确的实证证明伪装的适应度效益。因此，我们将把重点放在模仿树枝的毛毛虫上，以回答以下问题：一个物种是否能被证明从伪装而不是隐藏中特别受益？很可能物种通过隐密和伪装都受益，所以我们将使用相同的系统来探索在没有隐密的情况下是否会发生伪装；通过假面舞会和隐密术的共同作用，生存率能提高多少？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，因为它有时必须这样做来收集食物），那么很明显它是一只毛毛虫，而不是一根树枝。因此，如果捕食者通过经验学会看穿伪装，假面战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这样的经验，即伪装的物种出现在当地并且是可口的，那么伪装是否仍然有效；如果有效性受到伪装物种的本地密度和它们所伪装的东西的密度的影响。如前所述，假面舞会包括采用无生命物体的外观；然而，对许多物种来说，迁徙是它们觅食所必需的。这种冲突的解决方法似乎很可能是，假面者在白天视觉捕食者普遍存在的时候避免活动，只在晚上去觅食；这一假设也将通过文献调查和有目的设计的实验来检验。似乎许多物种只有在幼年和幼年时才会采用假面舞；当年龄较大时，切换到其他外观形式（主要是警告色）。同样，通过调查现有的跨物种比较文献，并通过有目的的设计实验，我们将试图找出这种经常剧烈变化的外观的原因。

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.