Departments of Biology and Mathematics, Grinnell College, Grinnell, Iowa 50112 USA;
Am J Bot. 2003 Sep;90(9):1333-40. doi: 10.3732/ajb.90.9.1333.
The strength and direction of natural selection on floral traits can vary spatially and temporally because of variation in the biotic and abiotic environment. High spatial variation in selection should lead to differentiation of floral traits among populations. In contrast, high temporal variation in selection should retard the evolution of population-specific floral phenotypes. To determine the relative importance of spatial vs. temporal variation in natural selection, we measured phenotypic selection on seven floral traits of the wildflowers Lobelia cardinalis and L. siphilitica in 1999 and 2000. Lobelia cardinalis experienced significant temporal variation in selection, whereas L. siphilitica experienced spatial variation in selection on the same traits. This variation in selection on floral traits was associated with spatial and temporal differences in the soil microenvironment. Although few studies of natural selection include spatial or temporal replicates, our results suggest that such replication is critical for understanding the distribution of phenotypes in nature.
由于生物和非生物环境的变化，自然选择对花部特征的强度和方向在空间和时间上可能会有所不同。选择的高空间变异性应该会导致种群间花部特征的分化。相比之下，选择的高时间变异性应该会减缓具有种群特异性的花部表型的进化。为了确定自然选择中空间变异性与时间变异性的相对重要性，我们在 1999 年和 2000 年测量了野生植物半边莲和半边莲的七个花部特征的表型选择。半边莲经历了选择的显著时间变异性，而半边莲则在同一特征上经历了选择的空间变异性。花部特征选择的这种变化与土壤微环境的空间和时间差异有关。尽管很少有自然选择的研究包括空间或时间重复，但我们的结果表明，这种复制对于理解自然中表型的分布至关重要。
