Norwegian University of Science and Technology, Museum of Natural History and Archaeology, N-7491 Trondheim, Norway.
Ecology. 2011 Dec;92(12):2167-74. doi: 10.1890/11-0791.1.
Pollinators may mediate selection on traits affecting pollinator attraction and effectiveness, and while nonadditive effects of traits influencing the two components of pollination success are expected when seed production is pollen limited, they have been little studied. In a factorial design, we manipulated one putative attraction trait (number of flowers) and one putative efficiency trait (spur length) previously shown to be subject to pollinator-mediated selection in the deceptive orchid Dactylorhiza lapponica. Removal of half of the flowers reduced pollen removal, proportion of flowers receiving pollen, fruit set, and fruit mass compared to unmanipulated plants, while spur-tip removal increased fruit set and fruit mass but did not affect pollen removal or proportion of flowers receiving pollen. The effect of spur-tip removal on fruit mass was stronger among plants with intact number of flowers compared to plants with experimentally reduced number of flowers. The results demonstrate that number of flowers and spur length are direct targets of selection and may affect female fitness nonadditively. More generally, they show that the adaptive value of a given trait can depend on floral context and illustrate how experimental approaches can advance our understanding of the evolution of trait combinations.
传粉媒介可能会影响影响传粉者吸引力和效率的性状的选择，而当花粉限制种子生产时，预计影响授粉成功两个组成部分的性状会产生非加性效应，但这些效应研究得很少。在一个析因设计中，我们操纵了一个假定的吸引力性状（花朵数量）和一个假定的效率性状（距长度），先前的研究表明这些性状在欺骗性兰花 Dactylorhiza lapponica 中受到传粉媒介介导的选择。与未处理的植物相比，去除一半的花朵会减少花粉去除率、接受花粉的花朵比例、结实率和果实质量，而距尖端去除会增加结实率和果实质量，但不会影响花粉去除率或接受花粉的花朵比例。与实验性减少花朵数量的植物相比，完整花朵数量的植物中距尖端去除对果实质量的影响更强。结果表明，花朵数量和距长度是选择的直接目标，并且可能会以非加性方式影响雌性适合度。更一般地说，它们表明给定性状的适应值可能取决于花的结构，并说明了实验方法如何促进我们对性状组合进化的理解。
