Aristide Leandro, Dos Reis Sergio F, Machado Alessandra C, Lima Inaya, Lopes Ricardo T, Perez S Ivan
Division Antropologia, Facultad de Ciencias Naturales y Museo, UNLP, CONICET, 122 y 60, La Plata, Argentina.
Departamento de Biologia Animal, UNICAMP, Campinas, São Paulo, Brazil.
J Hum Evol. 2015 Apr;81:29-40. doi: 10.1016/j.jhevol.2015.02.003. Epub 2015 Mar 2.
The cranial base, composed of the midline and lateral basicranium, is a structurally important region of the skull associated with several key traits, which has been extensively studied in anthropology and primatology. In particular, most studies have focused on the association between midline cranial base flexion and relative brain size, or encephalization. However, variation in lateral basicranial morphology has been studied less thoroughly. Platyrrhines are a group of primates that experienced a major evolutionary radiation accompanied by extensive morphological diversification in Central and South America over a large temporal scale. Previous studies have also suggested that they underwent several evolutionarily independent processes of encephalization. Given these characteristics, platyrrhines present an excellent opportunity to study, on a large phylogenetic scale, the morphological correlates of primate diversification in brain size. In this study we explore the pattern of variation in basicranial morphology and its relationship with phylogenetic branching and with encephalization in platyrrhines. We quantify variation in the 3D shape of the midline and lateral basicranium and endocranial volumes in a large sample of platyrrhine species, employing high-resolution CT-scans and geometric morphometric techniques. We investigate the relationship between basicranial shape and encephalization using phylogenetic regression methods and calculate a measure of phylogenetic signal in the datasets. The results showed that phylogenetic structure is the most important dimension for understanding platyrrhine cranial base diversification; only Aotus species do not show concordance with our molecular phylogeny. Encephalization was only correlated with midline basicranial flexion, and species that exhibit convergence in their relative brain size do not display convergence in lateral basicranial shape. The evolution of basicranial variation in primates is probably more complex than previously believed, and understanding it will require further studies exploring the complex interactions between encephalization, brain shape, cranial base morphology, and ecological dimensions acting along the species divergence process.
颅底由中线颅底和外侧颅底组成，是颅骨结构上的重要区域，与多个关键特征相关，在人类学和灵长类学中已得到广泛研究。特别是，大多数研究都集中在中线颅底弯曲与相对脑容量或脑化之间的关联上。然而，外侧颅底形态的变异研究得并不那么深入。阔鼻猴是一类灵长类动物，在中南美洲经历了一次主要的进化辐射，伴随着大规模的形态多样化，时间跨度很长。先前的研究还表明，它们经历了几个进化上独立的脑化过程。鉴于这些特征，阔鼻猴为在大型系统发育规模上研究灵长类动物脑容量多样化的形态学关联提供了绝佳机会。在本研究中，我们探讨了阔鼻猴颅底形态的变异模式及其与系统发育分支以及脑化的关系。我们使用高分辨率CT扫描和几何形态测量技术，对大量阔鼻猴物种样本的中线和外侧颅底的三维形状以及颅内体积的变异进行了量化。我们使用系统发育回归方法研究颅底形状与脑化之间的关系，并计算数据集中的系统发育信号量度。结果表明，系统发育结构是理解阔鼻猴颅底多样化的最重要维度；只有夜猴属物种与我们的分子系统发育不一致。脑化仅与中线颅底弯曲相关，并且在相对脑容量上表现出趋同的物种在外侧颅底形状上并未表现出趋同。灵长类动物颅底变异的进化可能比以前认为的更为复杂，要理解这一点需要进一步研究，探索脑化、脑形状、颅底形态和沿着物种分化过程起作用的生态维度之间的复杂相互作用。
