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 <i>Anolis</i> 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 data set of relative dewlap size digitised from photographs of 184 anole species from across the genus' geographic 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（speciation）的关联存在两种明确路径：其一为性状数值影响物种形成速率，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（Anolis）蜥蜴的喉扇（dewlap））常与物种形成过程相关。喉扇是一类重要的视觉信号，在物种识别（species recognition）与性选择（sexual selection）中发挥作用，不同物种的喉扇在相对大小、色彩与图案上均存在差异。我们整理了一套基于该属分布范围内184种安乐蜥的照片数字化得到的喉扇相对大小数据集。我们采用系统发育比较方法（phylogenetic comparative methods）检验两项假说：其一为喉扇更大的类群对应更高的物种形成速率；其二为喉扇相对面积的演化分化符合物种形成驱动的演化模型。本研究未发现性状依赖型物种形成（trait-dependent speciation）的相关证据，表明更大的信号结构并未强化喉扇在促进物种形成过程中的作用。与之相反，我们观测到喉扇演化同时兼具物种形成驱动型与渐进式两种演化模式的信号，且在大陆支系的喉扇演化中，物种形成驱动型变化的信号尤为显著。这表明喉扇大小的演化分化与物种形成过程密切相关，提示分歧选择可能在该信号性状的宏观演化（macroevolution）中发挥了作用。