Submitted to: Journal Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1997
Publication Date: N/A
Citation: Interpretive Summary: This paper summarizes some of our thoughts on the conservation of rare plants found on the rangelands of the western United States. Most of these rare plant species are incapable of reproducing unless insects, usually native bees, move pollen from shedding anthers of one flower to receptive stigmas of other flowers, usually on different plants. Thus, for most of these rare plant species, it is inadequate to consider management plans to increase the likelihood of their survival without also considering the requirements of the insects (mostly native bees) that pollinate them. These native bees have other needs, including a place, usually in the ground or in dead wood, to build a nest to house their progeny, materials such as leaves, plant hairs, resin, etc. to prepare that nest, and pollen and nectar to feed their progeny. In some cases these resources can all be obtained within the general area occupied by the rare plant that they pollinate, but in other cases they cannot. In situations where all pollinator needs cannot be met within the habitat of the rare plant, then the protected area set aside to preserve that plant must be expanded so as to include areas that contain essential bee resources. Thus viewed, rare plants have some commonality with larger vertebrates deemed umbrella species, in that their preservation will also aid populations of species. plant must be expanded so as to include areas that contain essential bee resources. Thus viewed, rare plants have some commonality with larger vertebrates deemed umbrella species, in that their preservation will also aid populations of many other species that exist within the ecosystem.
Technical Abstract: Critical habitat of rare Angiosperms may extend well beyond the actual are occupied because of the dependence of many plant species on pollinators. Indeep, because of their need for sexual servicing, rare plants may be re- garded as uncharismatic "umbrella" species. Most of the 26 species of rare plants we have studied in the western U.S. since 1988, set fruit only when visited by pollinators, primarily native bees. Thus, management plans to conserve these plants must also acknowledge their pollinators. Such plans introduce factors not usually considered in rare plant conservation. First managers must find and defend that nesting habitat of bee populations (usually in the ground or in decaying wood), which is not conterminous with the rare plants that these bees pollinate. Second, to maintain healthy native bee populations may also require the encouragement of populations of other plant species with floral rewards that complement or supplement those eof the rare species. And third, in areas with rare species whose pollin- ators have long flight periods, such as bumble bees and species with more than one generation per year, acceptable floral rewards must be available throughout the growing season. We illustrate the need for such "extended care" of rare plants with examples from our field work. Application of the "extended care" concept increase the size of areas set aside for plants. and species with more than one generation per year, acceptable floral rewards must be available throughout the growing season. We illustrate the need for such "extended care" of rare plants with examples from our field work. Application of the "extended care" concept would increase the size of areas set aside for rare plants, and would