Data from: Semicircular canals in Anolis lizards: ecomorphological convergence and ecomorph affinities of fossil species

Anolis lizards are a model system for the study of adaptive radiation and convergent evolution. Greater Antillean anoles have repeatedly evolved six similar forms or ecomorphs: crown-giant, grass-bush, twig, trunk, trunk-crown and trunk-ground. Members of each ecomorph category possess a specific set of morphological, ecological and behavioural characteristics which have been acquired convergently. Here we test whether the semicircular canal system—the organ of balance during movement—is also convergent among ecomorphs, reflecting the shared sensory requirements of their ecological niches. As semicircular canal shape has been shown to reflect different locomotor strategies, we hypothesized that each Anolis ecomorph would have a unique canal morphology. Using three-dimensional semilandmarks and geometric morphometrics, semicircular canal shape was characterized in 41 Anolis species from the Greater Antilles and the relationship between canal shape and ecomorph grouping, phylogenetic history, size, head dimensions, and perch characteristics was assessed. Further, canal morphology of modern species was used to predict the ecomorph affinity of five fossil anoles from the Miocene of the Dominican Republic. Of the covariates tested, our study recovered ecomorph as the single-most important covariate of canal morphology in modern taxa; although phylogenetic history, size, and head dimensions also showed a small, yet significant correlation with shape. Surprisingly, perch characteristics were not found to be significant covariates of canal shape, even though they are important habitat variables. Using posterior probabilities, we found that the fossil anoles have different semicircular canals shapes to modern ecomorph groupings implying extinct anoles may have been interacting with their Miocene environment in different ways to modern Anolis species.

安乐蜥（Anolis lizards）是探究适应性辐射（adaptive radiation）与趋同演化（convergent evolution）的经典模式系统。大安的列斯群岛安乐蜥多次独立演化出六种高度相似的生态形态型（ecomorphs）：冠巨型、灌草丛型、枝栖型、干栖型、冠干型与地干型。每一类生态形态型的物种均拥有一套趋同演化形成的特定形态、生态与行为特征。本研究旨在验证：半规管系统（semicircular canal system）——动物运动时的平衡感知器官——在不同生态形态型间是否同样存在趋同演化，以反映其生态位共有的感官需求。已有研究证实半规管形态可反映不同的运动策略，据此我们提出假说：每一类安乐蜥生态形态型均拥有独特的半规管形态。我们借助三维半地标点（three-dimensional semilandmarks）与几何形态测量学（geometric morphometrics），对41种采自大安的列斯群岛的安乐蜥的半规管形态进行了定量表征，并评估了半规管形态与生态形态型分组、系统发育历史、体型、头部尺寸以及栖息基质特征之间的关联。此外，我们还利用现生物种的半规管形态数据，预测了来自多米尼加共和国中新世（Miocene）地层的5件化石安乐蜥的生态形态型归属。在本次测试的所有协变量中，研究确认生态形态型是现生类群半规管形态最关键的影响因子；尽管系统发育历史、体型与头部尺寸同样与半规管形态存在微弱但显著的相关性。令人意外的是，尽管栖息基质特征是重要的生境变量，却并未被证实对半规管形态存在显著影响。通过后验概率（posterior probabilities）分析，我们发现化石安乐蜥的半规管形态与现生生态形态型分组存在显著差异，这表明已灭绝的安乐蜥可能以与现生安乐蜥截然不同的方式，与其所处的中新世环境产生生态互动。