Cubo J, Ponton F, Laurin M, de Margerie E, Castanet J
Comparative Osteohistology, FRE CNRS 2696, Pierre et Marie Curie University, 75005 Paris, France.
Syst Biol. 2005 Aug;54(4):562-74. doi: 10.1080/10635150591003461.
In spite of the fact that the potential usefulness of bone histology in systematics has been discussed for over one and a half centuries, the presence of a phylogenetic signal in the variation of histological characters has rarely been assessed. A quantitative assessment of phylogenetic signal in bone histological characters could provide a justification for performing optimizations of these traits onto independently generated phylogenetic trees (as has been done in recent years). Here we present an investigation on the quantification of the phylogenetic signal in the following bone histological, microanatomical, and morphological traits in a sample of femora of 35 species of sauropsids: vascular density, vascular orientation, index of Haversian remodeling, cortical thickness, and cross-sectional area (bone size). For this purpose, we use two methods, regressions on distance matrices tested for significance using permutations (a Mantel test) and random tree length distribution. Within sauropsids, these bone microstructural traits have an optimal systematic value in archosaurs. In this taxon, a Mantel test shows that the phylogeny explains 81.8% of the variation of bone size and 86.2% of the variation of cortical thickness. In contrast, a Mantel test suggests that the phylogenetic signal in histological traits is weak: although the phylogeny explains 18.7% of the variation of vascular density in archosaurs, the phylogenetic signal is not significant either for vascular orientation or for the index of Haversian remodeling. However, Mantel tests seem to underestimate the proportion of variance of the dependent character explained by the phylogeny, as suggested by a PVR (phylogenetic eigenvector) analysis. We also deal with some complementary questions. First, we evaluate the functional dependence of bone vascular density on bone size by using phylogenetically independent contrasts. Second, we perform a variation partitioning analysis and show that the phylogenetic signal in bone vascular density is not a by-product of phylogentic signal in bone size. Finally, we analyze the evolution of cortical thickness in diapsids by using an optimization by squared change parsimony and discuss the functional significance of this character in terms of decreased buoyancy in crocodiles and mass saving in birds. These results are placed in the framework of the constructional morphology model, according to which the variation of a character in a clade has a historical (phylogenetic) component, a functional (adaptive) component, and a structural (architectural) component.
尽管骨组织学在系统分类学中的潜在用途已经被讨论了一个半多世纪，但组织学特征变异中系统发育信号的存在却很少被评估。对骨组织学特征中的系统发育信号进行定量评估，可以为将这些特征优化到独立生成的系统发育树上提供依据（近年来已经有人这样做了）。在这里，我们对35种蜥形纲动物股骨样本中的以下骨组织学、微观解剖学和形态学特征的系统发育信号进行了量化研究：血管密度、血管方向、哈弗斯系统重塑指数、皮质厚度和横截面积（骨大小）。为此，我们使用了两种方法，对距离矩阵进行回归并通过置换检验其显著性（曼特尔检验）以及随机树长分布。在蜥形纲动物中，这些骨微观结构特征在主龙类中具有最佳的系统分类价值。在这个分类单元中，曼特尔检验表明系统发育解释了骨大小变异的81.8%和皮质厚度变异的86.2%。相比之下，曼特尔检验表明组织学特征中的系统发育信号较弱：尽管系统发育解释了主龙类中血管密度变异的18.7%，但血管方向或哈弗斯系统重塑指数的系统发育信号并不显著。然而，如系统发育特征向量（PVR）分析所示，曼特尔检验似乎低估了系统发育所解释的依赖性状方差的比例。我们还处理了一些补充问题。首先，我们通过使用系统发育独立对比来评估骨血管密度对骨大小的功能依赖性。其次，我们进行了变异分配分析，并表明骨血管密度中的系统发育信号不是骨大小系统发育信号的副产品。最后，我们通过平方变化简约法优化分析了双孔类动物皮质厚度的进化，并从鳄鱼浮力降低和鸟类节省质量的角度讨论了这个特征的功能意义。这些结果被置于结构形态模型的框架内，根据该模型，一个类群中一个特征的变异具有历史（系统发育）成分、功能（适应性）成分和结构（建筑）成分。
