Goswami Anjali
Committee on Evolutionary Biology, University of Chicago, Chicago, IL, USA.
Evol Dev. 2007 May-Jun;9(3):290-8. doi: 10.1111/j.1525-142X.2007.00161.x.
Heterochrony, the temporal shifting of developmental events relative to each other, requires a degree of autonomy among those processes or structures. Modularity, the division of larger structures or processes into autonomous sets of internally integrated units, is often discussed in relation to the concept of heterochrony. However, the relationship between the developmental modules derived from studies of heterochrony and evolutionary modules, which should be of adaptive importance and relate to the genotype-phenotype map, has not been explicitly studied. I analyzed a series of sectioned and whole cleared-and-stained embryological and neonatal specimens, supplemented with published ontogenetic data, to test the hypothesis that bones within the same phenotypic modules, as determined by morphometric analysis, are developmentally integrated and will display coordinated heterochronic shifts across taxa. Modularity was analyzed in cranial bone ossification sequences of 12 therian mammals. A dataset of 12-18 developmental events was used to assess if modularity in developmental sequences corresponds to six phenotypic modules, derived from a recent morphometric analysis of cranial modularity in mammals. Kendall's tau was used to measure rank correlations, with randomization tests for significance. If modularity in developmental sequences corresponds to observed phenotypic modules, bones within a single phenotypic module should show integration of developmental timing, maintaining the same timing of ossification relative to each other, despite differences in overall ossification sequences across taxa. Analyses did not find any significant conservation of developmental timing within the six phenotypic modules, meaning that bones that are highly integrated in adult morphology are not significantly integrated in developmental timing.
异时性，即发育事件相对于彼此的时间性偏移，要求这些过程或结构之间具有一定程度的自主性。模块化，即将较大的结构或过程划分为内部整合单元的自主集合，常与异时性概念相关联进行讨论。然而，源自异时性研究的发育模块与进化模块之间的关系，尚未得到明确研究，而进化模块应具有适应性重要性并与基因型-表型图谱相关。我分析了一系列切片以及经过整体透明和染色处理的胚胎学和新生儿标本，并辅以已发表的个体发生数据，以检验以下假设：通过形态计量分析确定的同一表型模块内的骨骼在发育上是整合的，并且在不同分类群中会呈现出协调的异时性变化。对12种兽亚纲哺乳动物的颅骨骨化序列进行了模块化分析。使用一个包含12 - 18个发育事件的数据集来评估发育序列中的模块化是否与六个表型模块相对应，这六个表型模块源自最近对哺乳动物颅骨模块化的形态计量分析。使用肯德尔秩相关系数来测量秩相关性，并通过随机化检验确定其显著性。如果发育序列中的模块化与观察到的表型模块相对应，那么单个表型模块内的骨骼应显示出发育时间的整合，尽管不同分类群的整体骨化序列存在差异，但它们彼此之间的骨化时间应保持相同。分析未发现六个表型模块内发育时间有任何显著的保守性，这意味着在成年形态中高度整合的骨骼在发育时间上并没有显著整合。
