Data from: Comparative tests of the role of dewlap size in Anolis lizard speciation

Phenotypic traits may be linked to speciation in two distinct ways: character values may influence the rate of speciation or diversification in the trait may be associated with speciation events. Traits involved in signal transmission, such as the dewlap of Anolis lizards, are often involved in the speciation process. The dewlap is an important visual signal with roles in species recognition and sexual selection, and dewlaps vary among species in relative size as well as colour and pattern. We compile a dataset of relative dewlap size digitized from photographs of 184 anole species from across the genus' geographical range. We use phylogenetic comparative methods to test two hypotheses: that larger dewlaps are associated with higher speciation rates, and that relative dewlap area diversifies according to a speciational model of evolution. We find no evidence of trait-dependent speciation, indicating that larger signals do not enhance any role the dewlap has in promoting speciation. Instead, we find a signal of mixed speciational and gradual trait evolution, with a particularly strong signal of speciational change in the dewlaps of mainland lineages. This indicates that dewlap size diversifies in association with the speciation process, suggesting that divergent selection may play a role in the macroevolution of this signalling trait.

表型性状（phenotypic traits）与物种形成的关联存在两种明确路径：其一为性状数值可影响物种形成速率，其二为性状的演化分化与物种形成事件相关联。参与信号传递的性状（如安乐蜥属蜥蜴（Anolis lizards）的喉垂皮（dewlap））常参与物种形成进程。喉垂皮是一类关键的视觉信号，在物种识别与性选择中发挥重要作用，且不同物种的喉垂皮在相对尺寸、颜色与图案上均存在显著差异。本研究整合了一套基于全属分布范围内184种安乐蜥照片数字化得到的喉垂皮相对尺寸数据集。本研究采用系统发育比较方法（phylogenetic comparative methods）检验两项假说：一是喉垂皮尺寸越大，物种形成速率越高；二是喉垂皮相对面积的演化分化遵循物种形成型演化模型（speciational model of evolution）。研究未发现性状依赖型物种形成的相关证据，表明更大的信号结构并未强化喉垂皮在促进物种形成中的作用。与之相反，本研究发现了物种形成型与渐进式性状演化共存的演化信号，且在大陆支系的喉垂皮中，物种形成型变化的信号尤为显著。该结果表明喉垂皮尺寸的演化分化与物种形成进程密切相关，提示歧化选择可能在该信号性状的宏演化（macroevolution）过程中发挥重要作用。