Campbell Diane R
Department of Biology, University of Virginia, Charlottesville, VA, 22901.
Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224.
Evolution. 1989 Mar;43(2):318-334. doi: 10.1111/j.1558-5646.1989.tb04230.x.
I measured phenotypic selection of floral traits through both male and female functions of the hermaphroditic flowers of Ipomopsis aggregata (Pursh) V. Grant subsp. aggregata (Polemoniaceae). Fluorescent powdered dyes were used to track movement of pollen by hummingbirds and to measure pollen delivery to individual plants as well as pollen receipt. A phenotypic selection analysis revealed that selection due to male-male competition during pollination was capable of delaying flowering date and widening corolla tubes by 0.22 and 0.24 standard-deviation units, respectively, in a single generation. Several floral traits were highly correlated with each other. Multivariate selection analysis suggested that selection through male function directly favored late flowering as well as a sexual expression characterized by a short pistillate phase and long corollas. Selection intensities through male and female functions were of similar overall magnitude during the pollination stage of the life cycle, but different traits were favored, and selection sometimes acted in opposing directions. In 1985, selection through female function favored increased time spent in the pistillate phase and exserted stigmas (unlike selection through male function). As a result, individual plants varied greatly in functional gender. Plants that had exserted stigmas and narrow corollas and that spent a disproportionately long time in the pistillate phase achieved greater pollination success as females, while plants with the opposite traits achieved greater success as males. Moreover, female pollination success tended to increase, and male pollination success to decrease, with time spent in the pistillate phase, supporting a critical assumption of sex-allocation theory. Selection in the populations studied fluctuated from year to year and was highly sex-specific.
我通过聚合花烟草（Ipomopsis aggregata (Pursh) V. Grant subsp. aggregata，花荵科）雌雄同体花的雄性和雌性功能来测量花部性状的表型选择。使用荧光粉末染料追踪蜂鸟携带花粉的移动情况，并测量单个植株的花粉传递以及花粉接收情况。表型选择分析表明，在授粉过程中由于雄性间竞争导致的选择能够在一代中分别使花期延迟0.22个标准差单位、花冠管增宽0.24个标准差单位。几个花部性状之间高度相关。多变量选择分析表明，通过雄性功能进行的选择直接有利于晚花以及以短雌蕊期和长花冠为特征的性表达。在生命周期的授粉阶段，通过雄性和雌性功能的选择强度总体大小相似，但偏好不同的性状，而且选择有时作用方向相反。1985年，通过雌性功能进行的选择有利于增加雌蕊期时长和突出的柱头（与通过雄性功能进行的选择不同）。结果，个体植株在功能性别上差异很大。柱头突出、花冠狭窄且雌蕊期时长不成比例地长的植株作为雌性获得了更高的授粉成功率，而具有相反性状的植株作为雄性获得了更高的成功率。此外，随着雌蕊期时长增加，雌性授粉成功率趋于上升，而雄性授粉成功率趋于下降，这支持了性别分配理论的一个关键假设。所研究种群中的选择逐年波动，且具有高度的性别特异性。
