Data from: Why does the complexity of functionally equivalent signals vary across closely related species?

Animal signals are observed to vary widely in complexity among species, but why this should be the case—especially among closely related taxa—is unclear. Identifying the selective forces that drive these differences is important for understanding signal evolution, as well as the origins of communication more generally. We used a measure derived from information theory to quantify the complexity of visual territorial advertisement displays performed by males of closely related taxa of Puerto Rican Anolis lizard. In general, the information potential of visual displays appeared to be high compared to signals of other taxonomic groups (e.g., other lizards, birds). Nevertheless, there was still considerable variation in signal complexity among the Anolis taxa studied. We found a strong relationship between signal complexity and phylogeny for some aspects of the advertisement display traditionally thought to be important in species recognition. Other aspects of the display tended to vary independently of phylogeny, with differences in signal complexity among taxa reflecting the distance over which displays were typically viewed by territorial neighbours, and to some extent the number of sympatric congeners present in the environment. More generally, we highlight a little used, but tractable means of quantifying complexity in different species—and in different aspects of the same signal (the number, timing and type of components)—that can reveal the evolutionary processes generating increases (or decreases) in communicative complexity.

据观测，不同物种的动物信号复杂度差异悬殊，但造成这一现象的缘由——尤其是在近缘类群之间——至今尚未阐明。厘清驱动此类差异的选择压力，不仅有助于理解信号演化机制，也对揭示更广泛意义上的通讯行为起源具有重要意义。我们采用源自信息论（information theory）的量化方法，对波多黎各安乐蜥（Anolis）属近缘类群雄性的视觉领地宣告展示行为的复杂度进行了量化。总体而言，相较于其他类群（如其他蜥蜴、鸟类）的信号，该类视觉展示的信息潜力较高。但在所研究的安乐蜥类群间，信号复杂度仍存在显著差异。我们发现，在传统认知中对物种识别至关重要的部分宣告展示特征中，信号复杂度与系统发育（phylogeny）关系密切。而其余展示特征的变化则往往独立于系统发育，类群间的信号复杂度差异反映了领地相邻个体通常观测展示行为的有效距离，且在一定程度上与环境中共存的同域同属物种数量相关。更广泛而言，我们提出了一种尚未被广泛采用但易于实施的复杂度量化方案，可用于测定不同物种乃至同一信号的不同维度（组成成分的数量、时序与类型）的复杂度，该方案能够揭示驱动通讯复杂度增减的演化过程。