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

生物学的一个中心问题是，当亲属或祖先之间没有明显的先兆时，新的特征是如何进化的。水声通信以其丰富多样的信号特性，成为研究这一问题的模型系统。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负责塑造雄性信号，并推动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联系在一起，这样女性偏好的逐渐变化将与男性信号的相应变化平行。然而，最近的研究表明，这种联系可能并不像预期的那么紧密，女性的偏好和男性的信号可能相互独立地进化。这个项目检验了这样的假说，即遗传漂移(即由偶然事件引起的进化)在信号进化中发挥的作用比之前所承认的更大，这可能解释了男性和女性之间缺乏平行进化的原因。根据这一假设，在物种之间的信号差异方面，男性而不是女性处于领先地位。该项目包括五种都表现出一种新的叫声特征(双脉冲节律，其中叫声的脉冲被分组成对)和五种与较老的叫声特征密切相关的物种(单脉冲节奏，其中脉冲均匀分布)。该项目的目的是1)确定这类昆虫物种之间的进化关系，2)分析雄性的叫声模式，以寻找地理差异，并识别正在进化新的叫声模式的物种，以及3)识别雌性用来识别自己物种的雄性叫声的属性。声音识别将使用行走补偿器或球形跑步机来确定，该装置衡量不同男性叫声对倾听女性的吸引力。通过比较雄性叫声的模式和雌性用来识别这些叫声的属性集，就有可能确定导致物种之间信号多样化的进化机制。这个项目包括的物种数量使其跻身于交流进化的最大比较研究之列。这个项目将更好地理解新特征的进化，以及交流系统中男性和女性之间出现的模式。这项研究的广泛影响包括培养本科生和研究生进行综合、多方法的研究。为该项目开发的基础设施也将用于非正式和正式课程的教学。此外，行走补偿器是行为分析最强大的工具之一，将得到维护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.