Section of Ecology and Systematics, Corson Hall, Cornell University, Ithaca, New York 14853.
Am J Bot. 1999 Mar;86(3):333-43.
We investigated phenotypic variation in 15 traits in greenhouse-grown plants from 16 populations of Clarkia unguiculata from three elevational habitats and six latitudinal transects. Populations from the lowest and highest elevations were geographically and ecologically marginal within the species' range. We (1) describe patterns of trait variation with elevation and latitude; (2) compare latitutidinal variation between marginal and central areas of the species' range; and (3) compare patterns of variation within C. unguiculata to interspecific patterns within the genus. Although there was some evidence that traits varied clinally (i.e., increased/decreased monotonically) along environmental gradients, interaction effects between altitude and latitude dominated patterns of variation. For most traits, latitudinal trends at the low-elevation margin of the species' range differed from trends at mid- and high-elevation areas. Based on interspecific comparisons, populations at the hotter, more arid ends of both environmental gradients were expected to have rapid development, small flowers and vegetative size, low levels of herkogamy and protandry, and high rates of gas exchange. Instead, we found that while some traits were correlated with one gradient in the expected way (e.g., development time with elevation, gas-exchange physiology with latitude), all traits were not consistently associated with each other along both gradients, and intraspecific patterns of variation differed from interspecific patterns.
我们在温室中种植了来自三个海拔生境和六个纬度横断带的 16 个克拉克氏凤仙花种群的 15 个特征，研究了它们的表型变异。来自最低和最高海拔的种群在物种分布范围内的地理和生态上是边缘的。我们：（1）描述了随着海拔和纬度的特征变化模式；（2）比较了物种分布范围边缘和中心地区的纬度变化；（3）比较了 C. unguiculata 内部的变异模式与该属内种间的模式。尽管有一些证据表明特征沿着环境梯度呈连续变化（即单调增加/减少），但海拔和纬度之间的相互作用效应主导了变异模式。对于大多数特征，在物种分布范围的低海拔边缘的纬度趋势与中海拔和高海拔地区的趋势不同。基于种间比较，在两个环境梯度的较热、较干旱端的种群预计会有快速的发育、小花和营养体大小、较低的雌雄同花异位和雄蕊先熟程度，以及较高的气体交换率。然而，我们发现，虽然有些特征与一个梯度以预期的方式相关（例如，发育时间与海拔，气体交换生理学与纬度），但所有特征并不总是沿着两个梯度彼此一致相关，并且种内变异模式与种间模式不同。
