Department of Molecular Biology and Ecology of Plants, The Botanical Garden, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel.
New Phytol. 2015 Jan;205(1):369-77. doi: 10.1111/nph.12982. Epub 2014 Aug 26.
Pollinator-mediated selection is a major evolutionary driver of floral traits; yet, such selection has rarely been tested for floral extreme traits. The Oncocyclus irises have exceptionally large, dark-colored flowers, associated with night-sheltering pollination and heat reward by the dark flowers. We quantified phenotypic selection on stem length, floral size and color in two species of iris (Iris atropurpurea and I. haynei), using an experimental approach. We estimated selection gradients for both flowers open to natural pollination and for flowers receiving supplementary hand pollination, assuming that open-pollinated flowers are affected by all factors that could influence fitness, whereas supplementary pollination removes the possible influence of pollinators. We found evidence for pollinator-mediated selection to increase floral size and stem length in I. atropurpurea, but floral color in this species was not under pollinator-mediated selection. In I. haynei, no pollinator-mediated selection on any of the traits was detected. We conclude that the extreme floral size of I. atropurpurea has probably evolved as a result of pollinator behavior. Lack of such evidence for I. haynei and for the dark floral color in both species suggests that other non-pollinator agents are selecting for these prominent traits, or that phenotypic color variation in these irises is neutral.
传粉媒介介导的选择是花部特征进化的主要驱动力；然而，对于花部极端特征的这种选择很少被检验过。滇西鸢尾属植物的花具有非常大的、深色的花瓣，与夜间遮荫授粉和深色花朵的热奖励有关。我们使用实验方法量化了两种鸢尾属植物（紫斑鸢尾和黄花鸢尾）的茎长、花部大小和颜色的表型选择。我们估计了自然授粉和补充人工授粉的花朵的选择梯度，假设开放授粉的花朵受到所有可能影响适应性的因素的影响，而补充授粉则消除了传粉者可能的影响。我们发现，传粉媒介介导的选择在增加紫斑鸢尾的花部大小和茎长方面具有证据，但该物种的花部颜色不受传粉媒介介导的选择。在黄花鸢尾中，没有检测到任何性状的传粉媒介介导的选择。我们得出的结论是，紫斑鸢尾的极端花部大小可能是传粉者行为的结果。黄花鸢尾和两个物种的深色花部颜色都没有这种证据表明，其他非传粉者因素正在选择这些突出的特征，或者这些鸢尾的表型颜色变化是中性的。
