Gavrilets Sergey
Division of Environmental Studies, University of California, Davis, California, 95616.
N. I. Vavilov Institute of General Genetics, 3, Gubkin Street, 117809 GSP-1, Moscow B-333, Russia.
Evolution. 1996 Jun;50(3):1034-1041. doi: 10.1111/j.1558-5646.1996.tb02344.x.
A common conclusion in several recent publications devoted to the deterministic analysis of the third phase of Wright's shifting-balance theory is that under reasonable conditions phase three should proceed easily. I argue that the mathematical equations analyzed in these papers do not correspond to the biological situation they were meant to describe. I present a more appropriate study of the third phase of the shifting balance. My results show that the third phase can proceed only under much more restricted conditions than the previous studies suggested. Migration should be neither too strong not too weak relative to selection. The higher peak should be sufficiently dominant over the lower peak. Recombination can greatly reduce the plausibility of this phase or completely preclude peak shifts. A very important determinant of the ultimate outcome of the competition between different peaks is the topological structure of the network of demes. Peak shifts in two-dimensional networks of demes are more difficult than in one-dimensional networks. Phase three can be accomplished easiest if it is initiated in one of the peripheral demes.
最近几篇致力于对赖特氏迁移平衡理论第三阶段进行确定性分析的论文得出了一个共同结论，即在合理条件下，第三阶段应该能够顺利推进。我认为这些论文中所分析的数学方程与它们试图描述的生物学情形并不相符。我对迁移平衡的第三阶段进行了更恰当的研究。我的研究结果表明，第三阶段能够推进的条件比之前的研究所表明的要严格得多。相对于选择而言，迁移既不能太强也不能太弱。较高的峰值应该比较低的峰值具有足够的优势。重组会大大降低这个阶段发生的可能性，或者完全阻止峰值移动。不同峰值之间竞争最终结果的一个非常重要的决定因素是种群网络的拓扑结构。二维种群网络中的峰值移动比一维网络更困难。如果在其中一个外围种群中启动，第三阶段最容易完成。
