Analysis of the vascular floras of Utah, Colorado, and California suggest that a syndrome of life form and reproductive characteristics separates rare and common species. Woody plants are heavily underrepresented, and herbs are overrepresented on the official lists of endangered and/or threatened plants of the floras considered. Few of the rare species are descended from wind-pollinated ancestors, but instead are derived from the insect-pollinated stock. Theory suggests that many of the rare taxa will ultimately be shown to be self-pollinated. The date show a tendency for rare species to be better represented among taxa having bilaterally symmetrical as opposed to radially symmetrical flowers. In aggregate, the results suggest that most rare taxa are equipped for rapid exploitation of small, unusual habitats. Because many rare taxa appear to be dependent on insects for reproduction, their survival depends not only on appropriate physical habitat but also on healthy pollinator populations. Reproduction of outcrossed taxa will be handicapped by road dust and other sources of atmospheric particulate which might foul stigmatic surfaces. Self-pollinated taxa may have little generic variability and thus be especially sensitive to environmental modifications. Because most rare taxa have little generic variability and thus be especially sensitive to environmental modifications. Because most rare taxa are dicotyledonous herbs, herbicides such as 2, 4-D which have been widely used in vegetation management for control of broadleafed plants can be expected to have highly deleterious effects on populations of rare species in the target area.
Harper, K. T.
"Some reproductive and life history characteristics of rare plants and implications of management,"
Great Basin Naturalist Memoirs: Vol. 3
, Article 16.
Available at: http://scholarsarchive.byu.edu/gbnm/vol3/iss1/16