Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa.
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa.
New Phytol. 2017 Oct;216(1):24-31. doi: 10.1111/nph.14697. Epub 2017 Jul 24.
Explaining the variation in diversification rate across groups of plants has long been an important goal of botanists. In plants, complex scenarios involving a combination of extrinsic opportunities and intrinsic traits have been used to explain rapid diversification in certain groups. However, we feel that a very simple trait has been neglected from theories of plant diversification, namely plant height. Here, we argue that decreasing plant size should generally lead to an increase in speciation rate and a decrease in extinction rate. Theory suggests that all population genetic processes involved in speciation are influenced by plant size and its correlates, including seed dispersal distance, population size, generation time and the spatial scale at which plants perceive environmental heterogeneity. In addition, several of these variables, notably population size, also influence rates of extinction. We support our arguments with an empirical analysis showing that plant height is indeed negatively correlated with net diversification rate across families of angiosperms. Finally, we outline how the finer aspects of our hypothesis could be tested, at both micro- and macroevolutionary scales. In addition to strengthening our understanding of the effect of plant size on evolutionary processes, such a research agenda should contribute novel insights to speciation theory in general.
长期以来，解释植物群体多样化率的差异一直是植物学家的重要目标。在植物中，涉及外在机会和内在特征结合的复杂情况被用来解释某些群体的快速多样化。然而，我们认为，植物多样化理论忽略了一个非常简单的特征，即植物高度。在这里，我们认为植物体型的减小通常会导致物种形成率的增加和灭绝率的降低。理论表明，物种形成所涉及的所有种群遗传过程都受到植物大小及其相关因素的影响，包括种子散布距离、种群大小、世代时间以及植物感知环境异质性的空间尺度。此外，其中一些变量，特别是种群大小，也会影响灭绝率。我们通过实证分析支持我们的论点，该分析表明，在被子植物科中，植物高度与净多样化率确实呈负相关。最后，我们概述了如何在微观和宏观进化尺度上检验我们假设的更细微方面。除了加强我们对植物大小对进化过程的影响的理解外，这样的研究议程应该为一般的物种形成理论提供新的见解。
