Thompson, Jonathan E. and Susan R. Kephart.
Systematists use a broad range of evidence to construct classifications.
Micromorphological characters such as pollen and seeds can be used to reevaluate phylogenetic and cladistic relationships based on macromorphology. However, among close relatives within a genus, micromorphological differences are often slight. Pollen grains ranged in size from 35.25 0.98 m for S. parryi to 31.53 0.39 m for S. spaldingii , which also had the largest number of pores. Surprisingly, we also detected differences in pollen surface ornamentation among varieties of S. douglasii Hook, which falls within the same clade as S. parryi , and whose position relative to S. parryi had previously been disputed.