The evolution of novel traits in the acoustic communication system of Neoconocephalus (Orthoptera, Tettigoniidae)

生物学的一个核心问题是，当亲戚或祖先中没有明显的先兆时，新的特征是如何进化的。声通信以其信号特征的多样性为研究这一问题提供了一个模型系统。由于声音通信在生殖环境中起作用，人们普遍认为雌性对雄性信号特定属性的偏好是形成雄性信号的原因，并推动了不同物种之间信号的多样化。基于这一假设的模型要求男性和女性紧密相连，这样，女性偏好的逐渐转变将与男性信号的相应转变并行。然而，最近的研究表明，这种联系可能不像预期的那样紧密，女性的偏好和男性的信号可能相互独立地进化。该项目验证了遗传漂变（即偶然事件导致的进化）在信号进化中发挥的作用比之前所承认的更大的假设，并可以解释男性和女性之间缺乏平行进化的原因。根据这一假设，雄性而不是雌性在物种之间的信号分化中起主导作用。该项目包括五种katydids，它们都表现出一种新的叫声特征（双脉冲节奏，其中叫声的脉冲被分成成对）和五种与旧的叫声特征（单脉冲节奏，其中脉冲间隔均匀）密切相关的物种。该项目的目的是：1)确定该昆虫群体中物种之间的进化关系；2)分析雄性的呼叫模式，以寻找地理差异，并确定正在进化新呼叫模式的物种；3)确定雌性用于识别自己物种的雄性呼叫属性。叫声识别将通过行走补偿器或球形跑步机来确定，该装置可以测量不同雄性叫声对倾听的雌性的吸引力。通过比较雄性的叫声模式和雌性用来识别这些叫声的一组属性，将有可能确定导致物种间信号多样化的进化机制。这个项目中包含的物种数量使其成为最大的交流进化比较研究之一。这个项目将使人们更好地了解新特征的演变，以及在交流系统中男女之间出现的模式。本研究更广泛的影响包括培养本科生和研究生进行综合、多方法的研究。为这个项目开发的基础设施也将用于非正式和正式课程设置的教学。此外，行走补偿器，这是行为分析中最强大的工具之一，将被保留并提供给其他研究人员。

A central question of biology is how new traits evolve when there are no obvious precursors among relatives or ancestors. Acoustic communication, with its great diversity of signal traits, serves as a model system to study this question. Because acoustic communication functions in the context of reproduction, it has been widely assumed that female preferences for particular attributes of male signals are responsible for shaping male signals and for driving the diversification of signals among different species. Models based on this assumption require that males and females are tightly linked, such that a gradual shift in the preferences of females will be paralleled by a corresponding shift in the signals of males. Recent studies indicate that this linkage might not be as tight as expected, however, and that female preferences and male signals may evolve independently of each other.This project tests the hypothesis that genetic drift (i.e. evolution due to chance events) plays a stronger role in signal evolution than has been previously acknowledged and could account for the lack of parallel evolution between males and females. According to this hypothesis, males, rather than females, lead the way in the divergence of signals between species. The project includes five species of katydids that all exhibit a new call trait (double pulse rhythm, in which the pulses of the call are grouped into pairs) and five closely related species with the older call trait (single pulse rhythm, in which pulses are evenly spaced). The aims of the project are 1) to determine the evolutionary relationships among the species in this group of insects, 2) to analyze the call patterns of males, in order to look for geographical differences and to identify species that are in the process of evolving the new call pattern, and 3) to identify the attributes of male calls that females use for recognizing males of their own species. Call recognition will be determined using a walking compensator, or spherical treadmill, that measures the attractiveness of different male calls to listening females. By comparing the patterns of males calls with the set of attributes used by females to recognize those calls, it will be possible to identify the evolutionary mechanisms responsible for the diversification of signals among species.The number of species included in this project places it among the largest comparative studies of the evolution of communication. This project will provide a better understanding of the evolution of new traits, and of the patterns that emerge between males and females in communication systems.Broader impacts of this study include the training of undergraduate and graduate students in comprehensive, multi-approach research. The infrastructure developed for this project will also be used for instruction in both informal and formal course settings. Furthermore, the walking compensator, which is among the most powerful tools for behavioral analysis, will be maintained and made available to other researchers.