Interaction between floral color change and gender transition in the protandrous weed Saponaria officinalis

Natural selection has directed the evolution of floral traits so that pollinator visits are manipulated to maximize the fitness of individual plants by directing which other individual sires its seeds. In some plants, flowers change color over time and may have the ability to direct pollinators to rewarding flowers. In addition, by varying when pollen is available and when stigmas are receptive, protandrous plants can show variation in selfing rates. In this study, the association between color change and gender transition in flowers of Saponaria officinalis was examined. Anthocyanins were extracted from flowers of each gender stage to measure color using spectrophotometry. Female‐phase flowers were found to have significantly higher anthocyanin concentration than male‐phase flowers in both natural populations and experimental plots. This color change corresponded to a decrease in male sexual function, which was measured by the percentage of pollen grains stained as viable by lactophenol aniline blue and germinated on Brewbaker–Kwack media. Color change was phenotypically plastic. Plants grown in full sun had a more extensive color change than those grown in shaded experimental plots, and this effect was reversed the following year when the shading was removed. Pollinator observations documented both diurnal and nocturnal insect visitation. Fruit and seed set were equivalent on inflorescences bagged during daylight versus night, indicating that both diurnal and nocturnal insects are effective pollinators. If pollinators discriminate based on color, this could potentially reduce within‐plant floral visits and also geitonogamy. This study is the first to document flower color change and moth pollination in Saponaria officinalis.     

新西兰霍克湾普卡瓦湖岩芯植硅体分析所揭示的火山喷发事件后的植被变化

含火山灰层沉积的植硅体分析为了解植被对从空中下降的火山灰的反应提供新的信息。新西兰霍克湾的一个深197m钻孔的上部50m样品,提供了距今约50ka以来连续的植被记录。植硅体组合在4个主要的火山灰层都发生了明显的变化,表现在树木和灌木的急剧下降及禾草类和莎草科的繁盛。在每次火山灰降落后,都会有一系宁继后变化,木本类最早死亡,禾草类和莎草科取而代之,并很快占据裸露的地表。经过一个相当长的滞后时间,树木和／或灌木重新替代草本和莎草科。