Basic Mechanisms and Evolution of Acoustic Communication

声通信的基本机制和发展霍华德·卡尔·格哈特，首席研究员(作者姓名：H·卡尔·格哈特)通信影响信号者和接收者的生殖成功。因此，交流在进化和物种形成中发挥着关键作用，信号的差异往往是种群状况的可靠指标，这些种群在物理外观上几乎没有分歧。发送者和接收者施加的相互选择压力可能会在信号特性和感觉系统的选择性之间产生精确的匹配。原因是，发出不同信号的发送者不太可能吸引配偶，而具有非常独特偏好的接收者可能不会接受自己物种中的任何男性。然而，已经发现了一些例外的例子，在这些例子中，接受者更有效地被不是由他们自己的物种成员(=同种雄性)而是由那些密切相关的物种(=异种雄性)产生的信号所刺激。这些新奇的偏好被称为“隐藏偏好”，系统发育分析有时表明，这种偏好在进化时间中先于信号，因此这种偏好可以被认为是“预先存在的偏见”。该项目是对九种近缘关系密切的北美树蛙的信号特性和接收器偏好匹配的比较研究。雄性树蛙发出简单、刻板的声音，雌性树蛙通过走近发出声音的扬声器来回应这些声音或计算机合成的声音。使用合成叫声的回放实验将确定雌性在信号中进行选择时使用的关键物理属性(=偏好标准)。这些实验将为每个物种确定雌性是否对具有同种雄性典型特征的信号反应最好，或者其他物种的叫声或叫声元素是否可能更具吸引力，或者可能增强同种叫声的吸引力。可能会发现，与同种叫声特性的匹配在所有九个物种中都是好的，不匹配在所有物种中都很普遍，或者匹配在一些物种中发生，但在其他物种中不发生。无论这些实验的结果如何，系统发育分析--这将依赖于所有九个物种的形态和分子特征--将被用来暗示偏好和信号的进化顺序。这组特殊的树蛙还有两个特征，可以帮助解释一些物种匹配而另一些物种不匹配的模式。首先，群体中的一些物种经常与有类似叫声的近亲组成混合物种的合唱。在这里，可以预期发送者和接收者之间的匹配将是强有力的，以防止物种之间的交配。这个群体中的其他物种已经与任何其他有类似叫声的物种隔离了很长一段时间，而其他物种则是如此。这些是寻找不匹配(“隐藏偏好”和“先前存在的偏见”)的最佳候选者，因为这些偏见可能是祖先的特征，可以在没有与另一个物种交配的风险的情况下表现出来。其次，研究发现，群体中的一些物种的染色体数量是其他物种的两倍，染色体数量的变化会影响呼叫特性。染色体数量的这种变化也可能会影响女性的偏好，可能会跟踪呼叫的变化，或者导致发送者和接收者的不匹配。这一假设将通过研究青蛙的偏好来验证，这些青蛙的偏好是通过实验诱导额外的染色体组来检验的。

BASIC MECHANISMS AND EVOLUTION OF ACOUSTIC COMMUNICATION HOWARD CARL GERHARDT, JR., PRINCIPAL INVESTIGATOR(Name used as an author: H. Carl Gerhardt)Communication affects the reproductive success of signalers and receivers. Thus, communication plays a critical role in evolution and speciation, and differences in signals are often reliable indicators of the status of populations that have diverged little, if at all, in their physical appearance. Mutual selective pressures exerted by senders and receivers might be expected to generate precise matching between signal properties and the selectivity of the sensory system. The reason is that senders that produce very different signals are unlikely to attract mates, and receivers that have very unique preferences may not find any male of their own species acceptable. However, some exceptional examples have been found in which receivers are more effectively stimulated by signals that are not produced by members of their own species (=conspecific males), but by those of closely related species (=heterospecific males). These novel preferences have been called "hidden preferences," and a phylogenetic analysis sometimes shows that the preference predates signals in evolutionary time and can hence such preferences can be considered "pre-existing biases." This project is a comparative study of the matching of signal properties and receiver preferences in a complex of nine closely related North American treefrogs. Male treefrogs produce simple, stereotyped sounds, and females respond to these sounds or to synthetic, computer-generated sounds by approaching a speaker that emits them. Playback experiments using synthetic calls will identify the key physical properties (=preference criteria) used by females to select among signals. These experiments will determine for each species whether females respond best to signals with properties typical of conspecific males or whether calls or call-elements of other species might be more attractive or might enhance the attractiveness of conspecific calls. It might be found that matching to conspecific call properties is good in all nine species, that mismatches are prevalent in all species, or that matching occurs in some species but not in others. Regardless of the results of these experiments, a phylogenetic analysis - which will rely on morphological and molecular characters of all nine species - will be used to suggest the order of evolution of preferences and signals. This particular group of treefrogs also has two features that could help to explain a pattern in which matches occur in some species and mismatches in others. First, some species in the group routinely form mixed-species choruses with close relatives having similar calls. Here it might be expected that matching of senders and receivers will be strong in order to prevent mating between species. Other species in the group have been isolated from any other species with similar calls for long periods of time whereas others. These are the best candidates for finding mismatches ("hidden preferences" and "pre-existing biases") because these biases might be ancestral traits that can be expressed without the risk of mating with another species. Second, it has been found that some species in the group have twice the number of chromosomes of the other species and that changes in chromosome number affect call properties. Such a change in chromosome number might also affect female preferences in ways that could either track the changes in the calls or result in mismatches of senders and receivers. This hypothesis will be tested by studying the preferences of frogs with experimentally induced extra sets of chromosomes.