Dai Qiang, Zhan Xiangjiang, Lu Bin, Fu Jinzhong, Wang Qian, Qi Dunwu
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China ; The Key Laboratory for Conservation Biology of Endangered Wildlife, Sichuan Province, Chengdu Research Base of Giant Panda Breeding, Chengdu, Sichuan, China.
Organisms and Environment Division, Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom.
PLoS One. 2014 Jan 20;9(1):e85778. doi: 10.1371/journal.pone.0085778. eCollection 2014.
Range expansions may create a unique spatial genetic pattern characterized by alternate genetically homogeneous domains and allele frequency clines. Previous attempts to model range expansions have mainly focused on the loss of genetic diversity during expansions. Using individual-based models, we examined spatial genetic patterns under two expansion scenarios, boundary-limited range expansions (BLRE) and phenotype-limited range expansions (PhLRE). Our simulation revealed that the genetic diversity within populations lost quickly during the range expansion, while the genetic difference accumulated between populations. Consequently, accompanying the expansions, the overall diversity featured a slow decrease. Specifically, during BLREs, high speed of boundary motion facilitated the maintenance of total genetic diversity and sharpened genetic clines. Very slight constraints on boundary motion of BLREs drastically narrowed the homogeneous domains and increased the allele frequency fluctuations from those levels exhibited by PhLREs. Even stronger constraints, however, surprisingly brought the width of homogeneous domains and the allele frequency fluctuations back to the normal levels of PhLREs. Furthermore, high migration rates maintained a higher total genetic diversity than low ones did during PhLREs. Whereas, the total genetic diversities during BLREs showed a contrary pattern: higher when migration was low than those when migration was high. Besides, the increase of migration rates helped maintain a greater number of homogeneous domains during PhLREs, but their effects on the number of homogeneous domains during BLREs were not monotonous. Previous studies have showed that the homogenous domains can merge to form a few broad domains as the expansion went on, leading to fewer homogeneous domains. Our simulations, meanwhile, revealed that the range expansions could also rebuild homogeneous domains from the clines during the range expansion. It is possible that that the number of homogeneous domains was determined by the interaction of merging and newly emerging homogeneous domains.
范围扩张可能会产生一种独特的空间遗传模式，其特征是交替出现基因同质区域和等位基因频率渐变群。以往对范围扩张进行建模的尝试主要集中在扩张过程中遗传多样性的丧失。我们使用基于个体的模型，研究了两种扩张情景下的空间遗传模式，即边界限制范围扩张（BLRE）和表型限制范围扩张（PhLRE）。我们的模拟结果显示，在范围扩张过程中，种群内部的遗传多样性迅速丧失，而种群之间的遗传差异不断积累。因此，随着扩张的进行，总体多样性呈现出缓慢下降的趋势。具体而言，在边界限制范围扩张过程中，边界移动的高速促进了总遗传多样性的维持，并使遗传渐变群更加明显。对边界限制范围扩张的边界移动施加非常轻微的限制，会极大地缩小同质区域，并增加等位基因频率的波动，使其高于表型限制范围扩张所呈现的水平。然而，更强的限制却出人意料地使同质区域的宽度和等位基因频率的波动恢复到表型限制范围扩张的正常水平。此外，在表型限制范围扩张过程中，高迁移率比低迁移率维持了更高的总遗传多样性。而在边界限制范围扩张过程中，总遗传多样性呈现出相反的模式：迁移率低时高于迁移率高时。此外，迁移率的增加有助于在表型限制范围扩张过程中维持更多的同质区域，但它们对边界限制范围扩张过程中同质区域数量的影响并非单调的。先前的研究表明，随着扩张的进行，同质区域会合并形成一些较宽的区域，导致同质区域数量减少。与此同时，我们的模拟结果显示，范围扩张在扩张过程中也可以从渐变群中重建同质区域。同质区域的数量可能是由合并和新出现的同质区域之间的相互作用决定的。
