Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ, Cambridge, United Kingdom.
Evol Dev. 2014 Nov-Dec;16(6):373-81. doi: 10.1111/ede.12098. Epub 2014 Sep 11.
Morphospaces are quantitative representations of phenotype space that are widely used in studies of morphological evolution. Do current conceptualizations of morphospaces, however, appropriately reflect the evolutionary dynamics of organisms depicted in these spaces? Most empirical morphospace studies implicitly consider variability of biological forms as isotropic, but such a view appears inadequate when the properties of development mediating phenotypic changes are considered. Here, a trilobite case study is used to visualize the constraints imposed by development on the accessibility structure of morphospace. Variability in the resultant morphospace is strongly anisotropic and reveals discordances between the apparent range of possible phenotypes and their actual accessibility. Homoplasy, directionality, and asymmetry of evolutionary transitions appear as natural consequences of anisotropic variability and point out the limitation of morphological distance for evolutionary inference. Measures of distance in morphospace should be used with considerable caution and must be complemented with developmentally meaningful measures of evolutionary accessibility.
形态空间是表型空间的定量表示，在形态进化研究中被广泛应用。然而，目前的形态空间概念是否恰当地反映了这些空间中所描绘的生物体的进化动态？大多数经验形态空间研究隐含地认为生物形态的可变性是各向同性的，但当考虑到介导表型变化的发育特性时，这种观点似乎就不够充分了。在这里，通过三叶虫案例研究，可视化了发育对形态空间可及性结构的限制。由此产生的形态空间中的变异性具有强烈的各向异性，并揭示了可能的表型的明显范围与其实际可及性之间的不匹配。进化转变的同形性、方向性和不对称性似乎是各向异性变异性的自然结果，并指出了形态距离在进化推断中的局限性。形态空间中的距离度量应该谨慎使用，并且必须与具有发育意义的进化可及性度量相结合。
