DISSERTATION RESEARCH: The Function and Evolution of Rapid Color Change as a Social Signal

迄今为止，大多数关于视觉信号的研究都集中在动物的固定外观上，特别是它们的颜色。因此，从生态学、行为学和进化的角度来看，动态颜色信号仍然知之甚少。为了解决这一差异，研究人员之前对雄性面纱变色龙（Chamaeleo calyptratus）快速变色的控制和功能进行了详细的研究。然而，需要更广泛的背景来理解这些不寻常的颜色变化信号的进化起源和限制。在这项研究中，研究人员将对慢脚龙矮变色龙进行比较研究，以调查颜色变化信号是如何以及为什么进化的。矮变色龙在颜色变化和展示行为方面表现出明显的物种差异，使它们成为测试这种罕见信号类型的起源和功能的进化假设的理想选择。本研究旨在确定颜色变化是为了强调行为表现（反之亦然），还是作为一种独立于复杂行为的信号而出现，并评估颜色变化的潜在系统发育限制。除了在科学期刊上交流研究成果外，研究人员还将与亚利桑那州立大学和南非国家生物多样性研究所的外展项目合作，通过为亚利桑那州和南非的中学生定制的学习活动来分享主要的研究成果。为了更好地了解精致的行为表现是在复杂的颜色变化信号之前、之后还是同时进化的，研究人员将使用高清摄像机测量12种矮变色龙的种内行为（即攻击性/顺从性）和颜色信号的自然组合，记录每个物种自然栖息地中同种之间的分阶段、攻击性相互作用。在激烈的实验过程中，将拍摄动物的静态照片和视频，并在行为表现和快速颜色变化的过程中收集比色数据。Felsenstein的独立对比和系统发育广义最小二乘（PGLS）分析将用于评估显示色度和显示行为的多个方面之间的进化关系，并评估所有颜色和行为信号的系统发育信号的强度。最后，Mesquite程序将用于重建行为显示和颜色信号的祖先状态，试图解开信号阐述的顺序和模式。

To date, most studies on visual signals have focused on the fixed appearances of animals and, specifically, of their color. As a result, dynamic color signals remain poorly understood from ecological, behavioral, and evolutionary standpoints. To begin to address this discrepancy, the researchers previously conducted detailed studies of the control and function of rapid color change in male veiled chameleons, Chamaeleo calyptratus. However, a broader context is required to understand the evolutionary origins of and constraints on these unusual color change signals. In this study, the researchers will conduct a comparative study of Bradypodion dwarf chameleons to investigate how and why color change signals evolved. Dwarf chameleons exhibit marked variation in color change and display behavior among species, making them ideal for testing evolutionary hypotheses about the origin and function of this rare signal type. This study seeks to determine whether color change evolved to accentuate behavioral displays (or vice versa), or arose as a signal independent of complex behaviors and evaluate potential phylogenetic constraints on color change. In addition to communicating findings in scientific journals, the researchers will partner with outreach programs at Arizona State University and the South African National Biodiversity Institute to share major research findings via customized learning activities for middle school students in Arizona and South Africa. To better understand whether elaborate behavioral displays evolved before, after, or concurrently with complex color change signals, the researchers will measure natural suites of intraspecific behavioral (i.e. aggressive/submissive) and color signals in 12 species of dwarf chameleons using high-definition video cameras to record staged, aggressive interactions between conspecifics in each species natural habitat. Still photos of the animals, concurrently with video, will be taken during aggressive trials and colorimetric data will be collected throughout behavioral displays and bouts of rapid color change. Felsenstein's independent contrasts and phylogenetic generalized least squares (PGLS) analysis will be used to evaluate the evolutionary relationships between multiple aspects of display colorimetrics and display behaviors, and the strength of the phylogenetic signal will be evaluated for all color and behavioral signals. Lastly, the program Mesquite will be used to reconstruct ancestral states of behavioral displays and color signals in an attempt to disentangle the order and patterns of signal elaboration.