Vallejo-Marín Mario, Walker Catriona, Friston-Reilly Philip, Solís-Montero Lislie, Igic Boris
School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK
School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK.
Philos Trans R Soc Lond B Biol Sci. 2014 Aug 19;369(1649):20130256. doi: 10.1098/rstb.2013.0256.
Floral morphology determines the pattern of pollen transfer within and between individuals. In hermaphroditic species, the spatial arrangement of sexual organs influences the rate of self-pollination as well as the placement of pollen in different areas of the pollinator's body. Studying the evolutionary modification of floral morphology in closely related species offers an opportunity to investigate the causes and consequences of floral variation. Here, we investigate the recurrent modification of flower morphology in three closely related pairs of taxa in Solanum section Androceras (Solanaceae), a group characterized by the presence of two morphologically distinct types of anthers in the same flower (heteranthery). We use morphometric analyses of plants grown in a common garden to characterize and compare the changes in floral morphology observed in parallel evolutionary transitions from relatively larger to smaller flowers. Our results indicate that the transition to smaller flowers is associated with a reduction in the spatial separation of anthers and stigma, changes in the allometric relationships among floral traits, shifts in pollen allocation to the two anther morphs and reduced pollen : ovule ratios. We suggest that floral modification in this group reflects parallel evolution towards increased self-fertilization and discuss potential selective scenarios that may favour this recurrent shift in floral morphology and function.
花的形态决定了个体内部以及个体之间花粉传播的模式。在雌雄同体的物种中，性器官的空间排列会影响自花授粉的速率以及花粉在传粉者身体不同部位的分布。研究近缘物种花形态的进化变化，为探究花变异的原因和结果提供了一个机会。在这里，我们研究了茄科刺茄亚属中三对近缘类群花形态的反复变化，该类群的特点是同一朵花中存在两种形态不同的花药（异型花药）。我们对种植在共同花园中的植物进行形态测量分析，以描述和比较在从相对较大的花到较小的花的平行进化转变中观察到的花形态变化。我们的结果表明，向较小花的转变与花药和柱头空间距离的减小、花部性状之间异速生长关系的变化、花粉在两种花药形态间分配的改变以及花粉与胚珠比率的降低有关。我们认为该类群中的花形态变化反映了向更高自交率的平行进化，并讨论了可能有利于这种花形态和功能反复转变的潜在选择情景。
