Lebel Merav, Obolski Uri, Hadany Lilach, Sapir Yuval
The Botanical Garden Tel Aviv University Tel Aviv Israel.
School of Plant Sciences and Food Security Tel Aviv University Tel Aviv Israel.
Ecol Evol. 2017 Dec 20;8(2):1096-1106. doi: 10.1002/ece3.3683. eCollection 2018 Jan.
Diversity of flower traits is often proposed as the outcome of selection exerted by pollinators. Positive directional pollinator-mediated selection on floral size has been widely shown to reduce phenotypic variance. However, the underlying mechanism of maintaining within-population floral color polymorphism is poorly understood. Divergent selection, mediated by different pollinators or by both mutualists and antagonists, may create and maintain such polymorphism, but it has rarely been shown to result from differential behavior of one pollinator. We tested whether different behaviors of the same pollinators in morning and evening are associated with dimorphic floral trait in a Mediterranean annual plant that exhibits variable within-population frequencies of dark- and light-colored flower tubes. bee-flies, the major pollinators of , are mostly feeding in the flower in the morning, while in the evening they are mostly visiting the flowers for mating. In 2 years of studying in a single large population in the Carmel, Israel, we found in one year that dark-centered flowers received significantly higher fraction of visits in the morning. Fitness was positively affected by number of visits, but no fitness differences were found between tube-color morphs, suggesting that both morphs have similar pollination success. Using mediation analysis, we found that flower size was under positive directional pollinator-mediated selection in both years, but pollinator behavior did not explain entirely this selection, which was possibly mediated also by other agents, such as florivores or a-biotic stresses. While most pollinator-mediated selection studies show that flower size signals food reward, in , it may also signal for mating place, which may drive positive selection. While flower size found to be under pollinator-mediated selection in , differential behavior of the pollinators in morning and evening did not seem to explain flower color polymorphism.
花性状的多样性通常被认为是传粉者施加选择的结果。传粉者介导的对花大小的正向定向选择已被广泛证明会降低表型方差。然而，维持种群内花色多态性的潜在机制却鲜为人知。由不同传粉者或互利共生者和拮抗者共同介导的分歧选择，可能会产生并维持这种多态性，但很少有研究表明这是由一种传粉者的不同行为导致的。我们测试了在地中海一年生植物中，同一传粉者在早晨和晚上的不同行为是否与二态花性状相关，该植物种群中深色和浅色花管的频率各不相同。食蚜蝇是该植物的主要传粉者，它们大多在早晨在花中取食，而在晚上它们大多为交配而访花。在以色列卡梅尔的一个单一的大种群中进行了两年的研究，我们发现有一年深色花心的花在早晨接受的访花比例显著更高。适合度受到访花次数的正向影响，但在花管颜色形态之间未发现适合度差异，这表明两种形态具有相似的授粉成功率。通过中介分析，我们发现花大小在这两年中都受到传粉者介导的正向定向选择，但传粉者行为并不能完全解释这种选择，这可能也由其他因素介导，如花食者或非生物胁迫。虽然大多数传粉者介导的选择研究表明花大小表示食物奖励，但在该植物中，它也可能表示交配地点，这可能推动正向选择。虽然发现花大小受到传粉者介导的选择，但传粉者在早晨和晚上的不同行为似乎并不能解释花色多态性。
