Ecological and phylogenetic influence on mandible shape variation of South American caviomorph rodents (Rodentia: Hystricomorpha)

We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Chinchilloidea and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence of phylogeny and ecology on this variation was assessed through phylogenetic comparative methods. Most morphological variation was concentrated in condylar, coronoid and angular processes, and the diastema. Features potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process and diastema) were present only in octodontoids; cavioids showed opposite trends, which could represent a structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera distributed in the morphospace according to their classification into superfamilial clades. Phylogenetic signal for shape components was significant along phylogeny, while the relationship between mandibular shape and ecology was non significant when...

本研究采用几何形态测量学（geometric morphometrics）方法，对隶属于豚鼠总科（Cavioidea）、毛丝鼠总科（Chinchilloidea）与八齿鼠总科（Octodontoidea）这3个总科的17个南美豚形亚目啮齿类（caviomorph rodents）属群的下颌骨（mandible）形态变异开展分析。借助系统发育比较方法（phylogenetic comparative methods），本研究评估了系统发育与生态因子对该形态变异的相对影响。绝大多数形态变异集中于髁突（condylar process）、冠突（coronoid process）、角突（angular process）与齿隙（diastema）区域。仅八齿鼠总科类群拥有潜在利于掘土的形态特征——即高冠突与髁突、相对较短的角突与齿隙；豚鼠总科类群则呈现出相反的形态趋势，这或许代表了掘土习性（fossorial habits）所带来的结构约束。毛丝鼠总科类群的形态特征则处于中间状态。各属在形态空间（morphospace）中的分布与其所属总科演化支（clades）的分类结果一致。形态组分的系统发育信号（phylogenetic signal）在系统发育树上呈现显著相关性，而下颌骨形态与生态因子间的关联则在……时未表现出统计学显著性。