School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK.
AoB Plants. 2014 Mar 10;6(0). doi: 10.1093/aobpla/plu003. Print 2014.
Plant reproduction by means of flowers has long been thought to promote the success and diversification of angiosperms. It remains unclear, however, how this success has come about. Do flowers, and their capacity to have specialized functions, increase speciation rates or decrease extinction rates? Is floral specialization fundamental or incidental to the diversification? Some studies suggest that the conclusions we draw about the role of flowers in the diversification and increased phenotypic disparity (phenotypic diversity) of angiosperms depends on the system. For orchids, for example, specialized pollination may have increased speciation rates, in part because in most orchids pollen is packed in discrete units so that pollination is precise enough to contribute to reproductive isolation. In most plants, however, granular pollen results in low realized pollination precision, and thus key innovations involving flowers more likely reflect reduced extinction rates combined with opportunities for evolution of greater phenotypic disparity (phenotypic diversity) and occupation of new niches. Understanding the causes and consequences of the evolution of specialized flowers requires knowledge of both the selective regimes and the potential fitness trade-offs in using more than one pollinator functional group. The study of floral function and flowering-plant diversification remains a vibrant evolutionary field. Application of new methods, from measuring natural selection to estimating speciation rates, holds much promise for improving our understanding of the relationship between floral specialization and evolutionary success.
植物通过花朵进行繁殖的方式长期以来一直被认为有助于被子植物的成功和多样化。然而，这种成功是如何实现的还不清楚。花朵及其具有特殊功能的能力是增加物种形成率还是降低灭绝率？花朵的特化是物种多样化的基础还是偶然现象？一些研究表明，我们对花朵在被子植物多样化和表型差异（表型多样性）增加中的作用的结论取决于系统。例如，对于兰花来说，专门的传粉可能会增加物种形成率，部分原因是在大多数兰花中，花粉被包装在离散的单元中，因此传粉足够精确，可以促进生殖隔离。然而，在大多数植物中，颗粒状的花粉导致实现传粉的精度较低，因此涉及花朵的关键创新更可能反映出灭绝率降低，同时有机会进化出更大的表型差异（表型多样性）并占据新的生态位。了解特化花朵的进化原因和后果需要了解使用多个传粉者功能群的选择机制和潜在的适应度权衡。研究花朵功能和开花植物多样化仍然是一个充满活力的进化领域。应用新方法，从测量自然选择到估计物种形成率，为提高我们对花朵特化与进化成功之间关系的理解提供了很大的希望。
