Harder Lawrence D, Johnson Steven D
Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01 Scottsville, Pietermaritzburg 3209, South Africa.
New Phytol. 2009 Aug;183(3):530-545. doi: 10.1111/j.1469-8137.2009.02914.x. Epub 2009 Jun 22.
Although not 'a professed botanist', Charles Darwin made seminal contributions to understanding of floral and inflorescence function while seeking evidence of adaptation by natural selection. This review considers the legacy of Darwin's ideas from three perspectives. First, we examine the process of floral and inflorescence adaptation by surveying studies of phenotypic selection, heritability and selection responses. Despite widespread phenotypic and genetic capacity for natural selection, only one-third of estimates indicate phenotypic selection. Second, we evaluate experimental studies of floral and inflorescence function and find that they usually demonstrate that reproductive traits represent adaptations. Finally, we consider the role of adaptation in floral diversification. Despite different diversification modes (coevolution, divergent use of the same pollen vector, pollinator shifts), evidence of pollination ecotypes and phylogenetic patterns suggests that adaptation commonly contributes to floral diversity. Thus, this review reveals a contrast between the inconsistent occurrence of phenotypic selection and convincing experimental and comparative evidence that floral traits are adaptations. Rather than rejecting Darwin's hypotheses about floral evolution, this contrast suggests that the tempo of creative selection varies, with strong, consistent selection during episodes of diversification, but relatively weak and inconsistent selection during longer, 'normal' periods of relative phenotypic stasis.
尽管并非“公认的植物学家”,但查尔斯·达尔文在通过自然选择寻找适应证据的过程中,对花和花序功能的理解做出了开创性贡献。本综述从三个角度审视了达尔文思想的遗产。首先,我们通过调查表型选择、遗传力和选择反应的研究,考察花和花序的适应过程。尽管自然选择具有广泛的表型和遗传能力,但只有三分之一的估计表明存在表型选择。其次,我们评估了花和花序功能的实验研究,发现这些研究通常表明生殖性状代表适应。最后,我们考虑适应在花多样化中的作用。尽管存在不同的多样化模式(协同进化、对同一花粉载体的不同利用、传粉者转移),但传粉生态型和系统发育模式的证据表明,适应通常有助于花的多样性。因此,本综述揭示了表型选择的不一致出现与花性状是适应这一令人信服的实验和比较证据之间的对比。这种对比并非否定达尔文关于花进化的假设,而是表明创造性选择的节奏各不相同,在多样化时期有强烈、一致的选择,但在相对表型停滞的较长“正常”时期选择相对较弱且不一致。