Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, CNRS, Université Lyon 1, 69622, Villeurbanne, France.
BMC Evol Biol. 2012 Aug 8;12:141. doi: 10.1186/1471-2148-12-141.
Hybridization is often seen as a process dampening phenotypic differences accumulated between diverging evolutionary units. For a complex trait comprising several relatively independent modules, hybridization may however simply generate new phenotypes, by combining into a new mosaic modules inherited from each parental groups and parts intermediate with respect to the parental groups. We tested this hypothesis by studying mandible size and shape in a set of first and second generation hybrids resulting from inbred wild-derived laboratory strains documenting two subspecies of house mice, Musmusculus domesticus and Musmusculus musculus. Phenotypic variation of the mandible was divided into nested partitions of developmental, evolutionary and functional modules.
The size and shape of the modules were differently influenced by hybridization. Some modules seemed to be the result of typical additive effects with hybrids intermediate between parents, some displayed a pattern expected in the case of monogenic dominance, whereas in other modules, hybrids were transgressive. The result is interpreted as the production of novel mandible morphologies. Beyond this modularity, modules in functional interaction tended to display significant covariations.
Modularity emerges as a source of novel morphological variation by its simple potential to combine different parts of the parental phenotypes into a novel offspring mosaic of modules. This effect is partly counterbalanced by bone remodeling insuring an integration of the mosaic mandible into a functional ensemble, adding a non-genetic component to the production of transgressive phenotypes in hybrids.
杂交通常被视为一种过程，削弱了在分化的进化单位之间积累的表型差异。然而，对于一个由几个相对独立的模块组成的复杂性状，杂交可能只是通过将来自每个亲本群体的模块组合成一个新的嵌合体，以及与亲本群体之间的中间部分，从而产生新的表型。我们通过研究来自于近交野生衍生实验室品系的第一代和第二代杂种的下颚大小和形状来检验这一假设，这些品系记录了家鼠的两个亚种，即 Musmusculus domesticus 和 Musmusculus musculus。下颚的表型变异被分为发育、进化和功能模块的嵌套分区。
杂交对模块的大小和形状有不同的影响。一些模块似乎是典型的加性效应的结果，杂种处于父母代之间的中间位置，一些模块显示出在单基因显性情况下预期的模式，而在其他模块中，杂种是越界的。结果被解释为产生新的下颚形态。除了这种模块性之外，功能相互作用的模块往往表现出显著的协变。
模块性通过其将亲本表型的不同部分组合成一个新的后代嵌合体模块的简单潜力，成为新的形态变异的来源。这种效应部分被骨骼重塑所抵消，骨骼重塑确保了嵌合体下颚的整合到一个功能整体中，为杂种中越界表型的产生增加了一个非遗传成分。
