Department of Biology, University of Central Florida, Orlando, Florida, 32816, USA.
Department of Biology, University of Florida, Gainesville, Florida, 32611, USA.
Am J Bot. 2018 Oct;105(10):1631-1642. doi: 10.1002/ajb2.1161. Epub 2018 Sep 21.
Autopolyploidy, or whole-genome duplication within a species, leads to closely related cytotypes in one geographic location. One hypothesized mechanism by which autopolyploids become established is climatic niche divergence from their diploid progenitor. Here we tested this hypothesis in diploid, triploid, and tetraploid Galax urceolata (Diapensiaceae) and predicted the effects of climate change on the relative distributions of these cytotypes.
We investigated whether climatic niche divergence has shaped the current distributions of Galax urceolata cytotypes in eastern North America using climatic niche modeling, multivariate analyses of environmental space, and geographic range analyses. We then projected the models of the three cytotypes onto an ensemble of future climate maps to determine how the distributions might be altered over time.
All cytotypes are geographically sympatric; however, climatic niche contraction and a slight niche shift of the tetraploids was observed relative to that of the diploids. Climate projections for all diploid and tetraploid cytotypes showed substantial range contraction without much, or any, range shift, suggesting that Galax urceolata will likely go extinct in nature as mountain refugia become warmer.
Galax urceolata tetraploids occupy a slightly wetter habitat than that of their diploid progenitors. While we cannot take into account future adaptation, our models suggest extensive decreases in range distributions for both diploid and tetraploid G. urceolata based on climate change projections. Galax urceolata may therefore be under extreme threat due to loss of suitable habitat, and conservation efforts will be needed.
自体多倍体，即在一个物种内发生的全基因组复制，会导致同一地理位置出现亲缘关系密切的细胞型。自体多倍体得以建立的一个假设机制是，它们与二倍体祖先在气候生态位上发生分歧。在这里，我们在二倍体、三倍体和四倍体 Galax urceolata（岩白菜科）中检验了这一假说，并预测了气候变化对这些细胞型相对分布的影响。
我们通过气候生态位模型、环境空间的多元分析以及地理范围分析，调查了气候生态位的分歧是否塑造了北美东部 Galax urceolata 细胞型的当前分布。然后，我们将这三个细胞型的模型投射到一组未来的气候图上，以确定随着时间的推移，这些分布可能会发生怎样的变化。
所有细胞型在地理上都是同域的；然而，与二倍体相比，四倍体的气候生态位收缩，略有生态位转移。所有二倍体和四倍体细胞型的气候预测都显示出范围的大幅度收缩，而没有太多或任何范围的转移，这表明随着山地避难所变暖，Galax urceolata 可能会在自然界中灭绝。
Galax urceolata 四倍体比其二倍体祖先占据稍湿润的栖息地。虽然我们不能考虑未来的适应，但我们的模型表明，基于气候变化的预测，二倍体和四倍体 G. urceolata 的范围分布将会大幅减少。因此，Galax urceolata 可能由于适宜栖息地的丧失而面临极端威胁，需要采取保护措施。
