Otto S P, Whitton J
Department of Zoology and Department of Botany, University of British Columbia, Vancouver BC V6T 1Z4 Canada.
Annu Rev Genet. 2000;34:401-437. doi: 10.1146/annurev.genet.34.1.401.
Changes in ploidy occurred early in the diversification of some animal and plant lineages and represent an ongoing phenomenon in others. While the prevalence of polyploid lineages indicates that this phenomenon is a common and successful evolutionary transition, whether polyploidization itself has a significant effect on patterns and rates of diversification remains an open question. Here we review evidence for the creative role of polyploidy in evolution. We present new estimates for the incidence of polyploidy in ferns and flowering plants based on a simple model describing transitions between odd and even base chromosome numbers. These new estimates indicate that ploidy changes may represent from 2 to 4% of speciation events in flowering plants and 7% in ferns. Speciation via polyploidy is likely to be one of the more predominant modes of sympatric speciation in plants, owing to its potentially broad-scale effects on gene regulation and developmental processes, effects that can produce immediate shifts in morphology, breeding system, and ecological tolerances. Theoretical models support the potential for increased adaptability in polyploid lineages. The evidence suggests that polyploidization can produce shifts in genetic systems and phenotypes that have the potential to result in increased evolutionary diversification, yet conclusive evidence that polyploidy has changed rates and patterns of diversification remains elusive.
倍性变化在一些动植物谱系多样化的早期就已发生，在其他谱系中则是一种持续存在的现象。虽然多倍体系谱的普遍性表明这种现象是一种常见且成功的进化转变，但多倍体化本身是否对多样化的模式和速率有重大影响仍是一个悬而未决的问题。在此，我们回顾多倍体在进化中发挥创造性作用的证据。我们基于一个描述奇偶数基数染色体数之间转变的简单模型，给出了蕨类植物和开花植物中多倍体发生率的新估计。这些新估计表明，倍性变化在开花植物的物种形成事件中可能占2%至4%，在蕨类植物中占7%。由于多倍体对基因调控和发育过程可能具有广泛影响，这些影响可导致形态、繁殖系统和生态耐受性的立即转变，通过多倍体形成物种很可能是植物同域物种形成中更主要的模式之一。理论模型支持多倍体系谱具有增强适应性的潜力。证据表明，多倍体化可导致遗传系统和表型发生转变，有可能增加进化多样性，但多倍体改变多样化速率和模式的确凿证据仍然难以捉摸。
