EAGER: Efficient coding and the evolution of animal signals

进化生物学中一个悬而未决的问题是，为什么许多动物在求偶时会使用复杂而夸张的颜色和声音。这些信号很有趣，不仅因为它们可能会引起捕食者的注意，还因为它们有多种形式，与密切相关的物种在重要方面有所不同。有效编码假说（EC）是一种新的解释，它指出人类视觉系统非常善于理解我们周围的世界，当某些东西容易理解时，它是首选的。因此，EC预测，雄性求偶信号将进化到与周围环境相匹配，以便它们容易被雌性接收者理解。这一预测与当前其他理论形成鲜明对比，这些理论预测求爱信号应该从它们的背景中脱颖而出，以便更容易被检测到。在这里，研究人员开发了统计和计算方法来测试EC，并将其应用于在美国东部发现的一组彩色鱼类。他们的主要目标是开发工具包，将EC应用于许多动物，并收集所需的信息，以设计直接测试EC的操作实验。沿着，他们还将为学生研究人员提供国际培训机会，并为巴尔的摩的学童提供课后活动。该项目探索高效编码在复杂动物信号多样化中的作用。高效编码是基于信息理论，描述了感觉系统如何最大限度地利用来自环境的信息，同时最大限度地减少冗余，从而限制编码相关信息所需的神经元数量。有效编码假说（EC）在这里适用于动物的信号设计，以询问是否视觉系统适应不同的栖息地可以有助于复杂的交配信号的多样化。EC超越了目前的感觉驱动信号检测框架，该框架预测动物信号通过最大化可检测性来最大化吸引力。EC预测，有吸引力的信号也应该与感官系统进化解码的环境统计参数相匹配。主要目标是建立EC在非人类的有效性，并适应人类在陆地环境中开发的方法，以了解复杂的视觉信号在动物之间的演变工具包。重点研究系统是北美淡水鱼属Etheostoma，称为镖鲈。雄性镖鲈的特征是具有多种生动、复杂、特定物种的婚礼色彩图案。虽然密切相关的镖鲈物种占据相似的栖息地，更远的相关物种有不同的栖息地偏好。中心假设是，适应镖鲈视觉系统编码的物种特异性栖息地的统计数字，有助于整个属的复杂的颜色模式的多样化。该假设的三个预测进行了测试。

An outstanding question in evolutionary biology is why many animals use complex and exaggerated colors and sounds during courtship. These signals are intriguing not only because they may attract the attention of predators, but also because they come in many forms, with closely-related species differing in important ways. The efficient coding hypothesis (EC) is a new explanation that states that the human visual system is very good at making sense of the world around us, and when something is easy to understand, it is preferred. EC therefore predicts that male courtship signals will evolve to match their surroundings so that they are easily understood by female receivers. This prediction is in stark contrast to other current theories which predict that courtship signals should stand out from their backgrounds so that they are more easily detected. Here the researchers develop statistical and computational methods to test EC, and apply them to a group of colorful fish found in the eastern United States. Their main objectives are to develop the toolkit to apply EC with many animals and to gather the information they need to design manipulative experiments that will test EC directly. Along the way, they will also provide international training opportunities for student researchers and after-school activities for school children in Baltimore. This project explores the role of efficient coding in the diversification of complex animal signals. Efficient coding is grounded in information theory and describes how sensory systems maximize information from the environment while minimizing redundancies, thus limiting the number of neurons required to encode relevant information. The efficient coding hypothesis (EC) is applied here to animal signal design to ask whether visual systems adapted to distinct habitats can contribute to the diversification of complex mating signals. EC goes beyond the current signal-detection framework of sensory drive, which predicts that animal signals maximize attractiveness by maximizing detectability. EC predicts that attractive signals also should match statistical parameters of the environment that sensory systems have evolved to decode. The main objectives are to establish the validity of EC in non-humans and to adapt methods developed for humans in terrestrial environments into a toolkit for understanding complex visual signal evolution across animals. The focal study system is the North American freshwater fish genus Etheostoma, called darters. Male darters are characterized by a diversity of vivid, complex, species-specific nuptial color patterns. Although closely-related darter species occupy similar habitats, more distantly-related species have distinct habitat preferences. The central hypothesis is that the adaptation of darter visual systems to encode the statistical regularities of species-specific habitats has contributed to the diversification of complex color patterns across the genus. Three predictions of that hypothesis are tested.