Keyte Anna L, Smith Kathleen K
Department of Pediatrics, Duke University Medical Center, Durham, NC, United States.
Department of Biology, Duke University, Durham, NC, United States.
Semin Cell Dev Biol. 2014 Oct;34:99-107. doi: 10.1016/j.semcdb.2014.06.015. Epub 2014 Jun 30.
Heterochrony, or a change in developmental timing, is an important mechanism of evolutionary change. Historically the concept of heterochrony has focused alternatively on changes in size and shape or changes in developmental sequence, but most have focused on the pattern of change. Few studies have examined changes in the mechanisms that embryos use to actually measure time during development. Recently, evolutionary studies focused on changes in distinct timekeeping mechanisms have appeared, and this review examines two such case studies: the evolution of increased segment number in snakes and the extreme rostral to caudal gradient of developmental maturation in marsupials. In both examples, heterochronic modifications of the somite clock have been important drivers of evolutionary change.
异时性，即发育时间的变化，是进化变化的一个重要机制。从历史上看，异时性的概念交替地聚焦于大小和形状的变化或发育顺序的变化，但大多数都集中在变化模式上。很少有研究考察胚胎在发育过程中实际用于测量时间的机制的变化。最近，聚焦于不同计时机制变化的进化研究已经出现，本综述考察了两个这样的案例研究：蛇类体节数量增加的进化以及有袋类动物从吻端到尾端发育成熟的极端梯度。在这两个例子中，体节时钟的异时性改变都是进化变化的重要驱动因素。
