School of Biological Sciences, University of Queensland, Brisbane 4072, Australia
School of Biological Sciences, University of Queensland, Brisbane 4072, Australia.
Proc Biol Sci. 2014 Aug 7;281(1788):20141091. doi: 10.1098/rspb.2014.1091.
Metamorphosis is common in animals, yet the genetic associations between life cycle stages are poorly understood. Given the radical changes that occur at metamorphosis, selection may differ before and after metamorphosis, and the extent that genetic associations between pre- and post-metamorphic traits constrain evolutionary change is a subject of considerable interest. In some instances, metamorphosis may allow the genetic decoupling of life cycle stages, whereas in others, metamorphosis could allow complementary responses to selection across the life cycle. Using a diallel breeding design, we measured viability at four ontogenetic stages (embryo, larval, juvenile and adult viability), in the ascidian Ciona intestinalis and examined the orientation of additive genetic variation with respect to the metamorphic boundary. We found support for one eigenvector of G: (gobsmax ), which contrasted larval viability against embryo viability and juvenile viability. Target matrix rotation confirmed that while gobsmax shows genetic associations can extend beyond metamorphosis, there is still considerable scope for decoupled phenotypic evolution. Therefore, although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage.
变态是动物中常见的现象,但生命周期各阶段之间的遗传关联尚不清楚。鉴于变态过程中会发生剧烈变化,变态前后的选择可能不同,并且前变态和后变态特征之间的遗传关联在多大程度上限制了进化变化是一个相当有兴趣的话题。在某些情况下,变态可能允许生命周期阶段的遗传解耦,而在其他情况下,变态可能允许整个生命周期的选择互补反应。我们使用双列杂交设计,在海鞘 Ciona intestinalis 中测量了四个个体发生阶段(胚胎、幼虫、幼体和成体活力)的活力,并检查了与变态边界有关的加性遗传变异的取向。我们支持 G 的一个本征向量(gobsmax),它将幼虫活力与胚胎活力和幼体活力进行对比。目标矩阵旋转证实,虽然 gobsmax 显示遗传关联可以延伸到变态之外,但仍然有很大的范围可以实现表型的解耦进化。因此,尽管变态过程中的遗传关联可能会限制可达到的表型范围,但变态边界两侧的特征仍然能够在每个生命周期阶段遇到的不同条件下独立进化。