Gori David F
Burke Museum DB-10, University of Washington, Seattle, WA, 98195.
Evolution. 1989 Jul;43(4):870-881. doi: 10.1111/j.1558-5646.1989.tb05184.x.
I examined the adaptive significance of two floral traits in the perennial herb, Lupinus argenteus: 1) the retention of corollas on "spent" flowers, i.e., flowers containing inviable pollen, unreceptive stigmas, and negligible pollinator rewards and 2) a change in corolla color of retained "spent" flowers, which is restricted to a spot on the banner petal. At anthesis, this spot is yellow, and approximately four days later, it changes to purple. After the change, purple flowers remain on plants an additional 5-7 days before corolla abscission occurs; purple flowers were avoided by pollinators, presumably because they contained less pollen (rewards) than yellow ones. I experimentally tested the hypothesis that purple flowers contribute to the floral display of the plant by removing varying numbers of spent flowers and assessing the effect on pollination visitation. Pollinators preferentially approached and foraged on plants with greater numbers of flowers per inflorescence; they did not discriminate between yellow (rewarding) and purple (nonrewarding) flowers at interplant distances greater than 0.4 meters but would preferentially forage on plants with more total flowers, even if these individuals contained fewer rewarding flowers. Thus, spent flowers increased the overall attractiveness of plants to pollinators. In theory, color change may benefit plants in two ways. First, by directing pollinators to rewarding flowers, the change may increase pollinator foraging efficiency, with the result that pollinators visit more flowers before leaving plants (pollinator-tenure mechanism). Second, by directing pollinators to receptive flowers, the color change may prevent incoming pollen from being wasted on unreceptive stigmas and may prevent collection of inviable pollen (pollination-efficiency mechanism). I tested the pollinator-tenure mechanism experimentally by removing pollen from yellow flowers, thereby reducing the reliability of the color-reward signal. Pollinators visited fewer total flowers on experimental plants than on controls, resulting in reduced seed production in one year.
1）“开过的”花（即含有不育花粉、无接受能力柱头且传粉者回报可忽略不计的花）上花冠的留存；2）留存的“开过的”花花冠颜色的变化，这种变化仅限于旗瓣上的一个斑点。在花期时，这个斑点是黄色的，大约四天后会变成紫色。变色后，紫色花朵在花冠脱落前会在植株上再留存5 - 7天；传粉者会避开紫色花朵，大概是因为它们所含的花粉（回报）比黄色花朵少。我通过去除不同数量的开过的花并评估对传粉访问的影响，对紫色花朵有助于植株花展示的假设进行了实验测试。传粉者优先接近并在每个花序花朵数量更多的植株上觅食；在植株间距离大于0.4米时，它们不会区分黄色（有回报的）和紫色（无回报的）花朵，但会优先在总花数更多的植株上觅食，即使这些个体中含有的有回报花朵较少。因此，开过的花增加了植株对传粉者的整体吸引力。理论上，颜色变化可能以两种方式使植物受益。首先，通过将传粉者引向有回报的花朵，这种变化可能提高传粉者的觅食效率，结果是传粉者在离开植株前会访问更多花朵（传粉者停留时间机制）。其次，通过将传粉者引向有接受能力的花朵，颜色变化可能防止传入的花粉浪费在无接受能力的柱头上，并可能防止采集不育花粉（授粉效率机制）。我通过去除黄色花朵上的花粉，从而降低颜色 - 回报信号的可靠性，对传粉者停留时间机制进行了实验测试。与对照植株相比，传粉者在实验植株上访问的总花朵数量更少，导致一年中的种子产量降低。
