Fabre Anne-Claire, Marigó Judit, Granatosky Michael C, Schmitt Daniel
Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA; UMR 7179, Muséum National d'Histoire Naturelle, Centre National de la Recherche Scientifique, Mécadev, 57 rue Cuvier, CP 55, 75231, Paris Cedex 5, France.
Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA; UMR 7207 CR2P - C.N.R.S., M.N.H.N., U.P.M.C.-Paris 6, Département Histoire de la Terre, Muséum National d'Histoire Naturelle, 75005, Paris, France; Institut Català de Paleontologia Miquel Crusafont (ICP), Universitat Autònoma de Barcelona, Edifici Z (ICTA-ICP), Carrer de les Columnes s/n, Campus UAB, 08193, Cerdanyola del Vallès, Barcelona, Spain.
J Hum Evol. 2017 Jul;108:11-30. doi: 10.1016/j.jhevol.2017.03.012. Epub 2017 Apr 28.
The evolution of primates is intimately linked to their initial invasion of an arboreal environment. However, moving and foraging in this milieu creates significant mechanical challenges related to the presence of substrates differing in their size and orientation. It is widely assumed that primates are behaviorally and anatomically adapted to movement on specific substrates, but few explicit tests of this relationship in an evolutionary context have been conducted. Without direct tests of form-function relationships in living primates it is impossible to reliably infer behavior in fossil taxa. In this study, we test a hypothesis of co-variation between forelimb morphology and the type of substrates used by strepsirrhines. If associations between anatomy and substrate use exist, these can then be applied to better understand limb anatomy of extinct primates. The co-variation between each forelimb long bone and the type of substrate used was studied in a phylogenetic context. Our results show that despite the presence of significant phylogenetic signal for each long bone of the forelimb, clear support use associations are present. A strong co-variation was found between the type of substrate used and the shape of the radius, with and without taking phylogeny into account, whereas co-variation was significant for the ulna only when taking phylogeny into account. Species that use a thin branch milieu show radii that are gracile and straight and have a distal articular shape that allows for a wide range of movements. In contrast, extant species that commonly use large supports show a relatively robust and curved radius with an increased surface area available for forearm and hand muscles in pronated posture. These results, especially for the radius, support the idea that strepsirrhine primates exhibit specific skeletal adaptations associated with the supports that they habitually move on. With these robust associations in hand it will be possible to explore the same variables in extinct early primates and primate relatives and thus improve the reliability of inferences concerning substrate use in early primates.
灵长类动物的进化与它们最初对树栖环境的入侵密切相关。然而，在这种环境中移动和觅食会带来重大的机械挑战，这与不同大小和方向的基质的存在有关。人们普遍认为，灵长类动物在行为和解剖结构上适应了在特定基质上的移动，但在进化背景下对这种关系进行的明确测试却很少。如果没有对现存灵长类动物的形态与功能关系进行直接测试，就不可能可靠地推断化石类群的行为。在本研究中，我们测试了一个关于前肢形态与狐猴型灵长类动物所使用基质类型之间协变的假设。如果解剖结构与基质使用之间存在关联，那么就可以应用这些关联来更好地理解已灭绝灵长类动物的肢体解剖结构。我们在系统发育背景下研究了每个前肢长骨与所使用基质类型之间的协变。我们的结果表明，尽管前肢的每根长骨都存在显著的系统发育信号，但仍存在明确的支持使用关联。无论是否考虑系统发育，在所使用的基质类型与桡骨形状之间都发现了强烈的协变，而尺骨只有在考虑系统发育时协变才显著。使用细树枝环境的物种的桡骨纤细且笔直，其远端关节形状允许进行广泛的运动。相比之下，通常使用大型支撑物的现存物种的桡骨相对粗壮且弯曲，在旋前姿势下，前臂和手部肌肉的可用表面积增加。这些结果，尤其是关于桡骨的结果，支持了狐猴型灵长类动物表现出与其习惯性移动的支撑物相关的特定骨骼适应的观点。有了这些强有力的关联，就有可能在已灭绝的早期灵长类动物和灵长类亲属中探索相同的变量，从而提高关于早期灵长类动物基质使用推断的可靠性。
