Departamento de Ciencias de la Vida, Facultad de Ciencias, Universidad de Alcalá, Alcalá de Henares (Madrid), Spain.
PLoS One. 2020 May 19;15(5):e0232736. doi: 10.1371/journal.pone.0232736. eCollection 2020.
Polyploidy has been an influential force in plant evolution, playing a crucial role in diversification. Differences in polyploid and diploid distributions have been long noted, with polyploid taxa especially abundant in harsh environments. These plants have higher photosynthetic rates and/or higher tolerance to water deficits. Moreover, there is data pointing to an increase in the rate of unreduced gamete formation by plants under conditions of stress. Accordingly, a higher frequency of polyploid individuals would be expected in populations living under extreme environments, a phenomenon that may be relevant when considering the origin of allopolyploid species. Hybridization between distinct autopolyploids is known to produce allopolyploids and hence, a high frequency of compatible autopolyploids in an area could enhance the formation of stable populations of the corresponding allopolyploid hybrid. Here we consider the allopolyploid species Gypsophila bermejoi G. López and its parental taxa G. struthium L. subsp. struthium and G. tomentosa L. We have used Species Distribution Models to locate areas with low bioclimatic suitability for both parental taxa during the Last Glacial Maximum (LGM), hypothesizing that the rate of tetraploid hybrid formation would be higher than expected where low suitability areas of both parental species overlap. We selected those areas taking into account the strict gypsophyllic nature of these taxa. There is data pointing to a post-glacial origin of the current G. bermejoi populations and according to our hypothesis, such locations could be centers for hybrid tetraploid formation or potential cradles of this species. Indeed, potential Mid-Holocene cradles were also identified in this manner. The evolution of bioclimatic suitability in both LGM and Mid-Holocene cradles was studied to assess the possible survival of the hybrids, and the current distribution of G. bermejoi proved to be consistent with our hypothesis.
多倍体在植物进化中一直是一股重要的力量，在多样化过程中发挥着关键作用。多倍体和二倍体的分布差异很早就被注意到了，多倍体类群尤其在恶劣环境中丰富。这些植物具有更高的光合速率和/或对水分亏缺的更高耐受性。此外，有数据表明，在胁迫条件下，植物减数分裂配子形成的速率增加。因此，在极端环境中生活的种群中，多倍体个体的频率应该会更高，这一现象在考虑异源多倍体物种的起源时可能是相关的。不同的同源多倍体之间的杂交会产生异源多倍体，因此，在一个地区同源多倍体的相容性频率高可能会增强相应异源多倍体杂种稳定种群的形成。在这里，我们考虑异源多倍体物种Gypsophila bermejoi G. López及其亲本种 G. struthium L. subsp. struthium 和 G. tomentosa L. 我们使用物种分布模型来定位在末次冰期（LGM）期间对双亲种生物气候适宜性低的区域，假设在双亲种低适宜性区域重叠的地方，四倍体杂种形成的速度会高于预期。我们选择了这些区域，考虑到这些类群严格的石竹科特性。有数据表明，目前的 G. bermejoi 种群起源于冰期后，根据我们的假设，这些位置可能是杂种四倍体形成的中心，或者是该物种的潜在摇篮。事实上，这种方法还确定了潜在的中全新世摇篮。研究了 LGM 和中全新世摇篮中的生物气候适宜性演变，以评估杂种的可能生存能力，并且 G. bermejoi 的当前分布与我们的假设一致。
