Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.
Evolution. 2013 Jun;67(6):1780-91. doi: 10.1111/evo.12065. Epub 2013 Mar 1.
Polyploid organisms often have different geographic ranges than their diploid relatives. However, it is unclear whether this divergence is maintained by adaptation or results from historical differences in colonization. Here, we conducted a reciprocal transplant experiment with diploid and autotetraploid Chamerion angustifolium to test for adaptation at the ploidy and population level. In the Rocky Mountains, pure diploid populations occur at high elevations and pure autotetraploid populations occur at low elevations with mixed ploidy populations between. We planted 3134 seedlings in 2004 and 3890 juveniles (bolting) in 2005 among nine plots, three in each of the diploid, mixed ploidy, and tetraploid zones, and monitored survival until 2008. For both seedlings and juvenile plants, elevation significantly influenced survival. The juvenile plants also showed a significant ploidy by elevation interaction, indicating that diploids and tetraploids survived best at their native elevations. In contrast, we found no evidence of local adaptation to plot within elevation. This suggests that the current distribution of diploids and tetraploids across elevations is the result of adaptation and that genome duplication may have facilitated the invasion of lower elevation habitats by limiting the movement of maladapted alleles from diploid populations at higher elevations.
多倍体生物的地理分布范围通常与其二倍体亲属不同。然而，这种分化是由适应还是由历史上的殖民差异所维持尚不清楚。在这里，我们对二倍体和同源四倍体 Chamerion angustifolium 进行了相互移植实验，以在倍性和种群水平上测试适应。在落基山脉，纯二倍体种群分布在高海拔地区，纯同源四倍体种群分布在低海拔地区，而在两者之间存在混合倍性种群。我们于 2004 年种植了 3134 株幼苗，于 2005 年种植了 3890 株幼株（抽薹），共 9 个地块，每个地块分为二倍体、混合倍性和四倍体区各 3 个，并监测了它们的存活情况，直到 2008 年。对于幼苗和幼株，海拔显著影响了它们的存活。幼株还表现出显著的倍性与海拔的互作，表明二倍体和四倍体在其原生海拔地区的存活率最高。相比之下，我们没有发现对海拔内的斑块有局部适应的证据。这表明，当前二倍体和四倍体在海拔上的分布是适应的结果，基因组复制可能通过限制来自高海拔地区的不适应等位基因的移动，促进了低海拔生境的入侵。
