Table_2_Indirect Selection on Flower Color in Silene littorea.xlsx

Flower color, as other floral traits, may suffer conflicting selective pressures mediated by both mutualists and antagonists. The maintenance of intraspecific flower color variability has been usually explained as a result of direct selection by biotic agents. However, flower color might also be under indirect selection through correlated traits, since correlations among flower traits are frequent. In this study, we aimed to find out how flower color variability is maintained in two nearby populations of Silene littorea that consistently differ in the proportions of white-flowered plants. To do that, we assessed natural selection on floral color and correlated traits by means of phenotypic selection analysis and path analysis. Strong directional selection on floral display and flower production was found in both populations through either male or female fitness. Flower color had a negative indirect effect on the total male and female fitness in Melide population, as plants with lighter corollas produced more flowers. In contrast, in Barra population, plants with darker corollas produced more flowers and have darker calices, which in turn were selected. Our results suggest that the prevalence of white-flowered plants in Melide and pink-flowered plants in Barra is a result of indirect selection through correlated flower traits and not a result of direct selection of either pollinators or herbivores on color.

与其他花部性状一样，花色可能同时受到互利共生生物与拮抗生物介导的冲突性选择压力。物种内花色变异的维持通常被解释为生物因子直接选择的结果。然而，由于花部性状间普遍存在关联，花色也可能通过相关性状受到间接选择。本研究旨在探究两个相邻的海滨蝇子草（Silene littorea）种群中花色变异的维持机制，这两个种群的白花植株占比始终存在差异。为此，我们通过表型选择分析（phenotypic selection analysis）和通径分析（path analysis）评估了花色及相关性状的自然选择作用。两个种群均通过雄性或雌性适合度，检测到了对花展示与花产量的强烈定向选择。在梅利德（Melide）种群中，花色对总雄性与雌性适合度存在负向间接效应：花冠颜色更浅的植株花产量更高。与之相反，在巴拉（Barra）种群中，花冠颜色更深的植株花产量更高且花萼颜色更深，而花萼性状恰好受到选择作用。本研究结果表明，梅利德种群中白花植株占优、巴拉种群中粉花植株占优的现象，是通过花部相关性状产生的间接选择所致，而非传粉者或植食动物对花色的直接选择结果。