Klopfstein Seraina, Currat Mathias, Excoffier Laurent
Computational and Molecular Population Genetics Lab, Institute of Zoology, University of Bern, Bern, Switzerland.
Mol Biol Evol. 2006 Mar;23(3):482-90. doi: 10.1093/molbev/msj057. Epub 2005 Nov 9.
Many species, including humans, have dramatically expanded their range in the past, and such range expansions had certainly an impact on their genetic diversity. For example, mutations arising in populations at the edge of a range expansion can sometimes surf on the wave of advance and thus reach a larger spatial distribution and a much higher frequency than would be expected in stationary populations. We study here this surfing phenomenon in more detail, by performing extensive computer simulations under a two-dimensional stepping-stone model. We find that the probability of survival of a new mutation depends to a large degree on its proximity to the edge of the wave. Demographic factors such as deme size, migration rate, and local growth rate also influence the fate of these new mutations. We also find that the final spatial and frequency distributions depend on the local deme size of a subdivided population. This latter result is discussed in the light of human expansions in Europe as it should allow one to distinguish between mutations having spread with Paleolithic or Neolithic expansions. By favoring the spread of new mutations, a consequence of the surfing phenomenon is to increase the rate of evolution of spatially expanding populations.
包括人类在内的许多物种在过去都极大地扩展了其分布范围，这种分布范围的扩展无疑对它们的遗传多样性产生了影响。例如，在分布范围扩展边缘的种群中出现的突变，有时会搭乘前进的浪潮，从而达到比稳定种群中预期更大的空间分布和更高的频率。我们在此通过在二维 stepping-stone 模型下进行广泛的计算机模拟，更详细地研究这种“冲浪”现象。我们发现，新突变的存活概率在很大程度上取决于其与浪潮边缘的接近程度。诸如群落大小、迁移率和局部增长率等人口统计学因素也会影响这些新突变的命运。我们还发现，最终的空间和频率分布取决于细分种群的局部群落大小。根据欧洲的人类扩张情况对后一个结果进行了讨论，因为它应该能够区分随着旧石器时代或新石器时代扩张而传播的突变。通过促进新突变的传播，“冲浪”现象的一个后果是增加空间扩张种群的进化速度。
