An 11-year Ecological Study of a Rare Prairie Perennial (Asclepias meadii): Implications for Monitoring and Management

Abstract

Mead's milkweed, Asclepias meadii, is a rare long-lived perennial of North American tallgrass prairies. Stems of this clonal species are spatially aggregated and, therefore, observing survivorship and flowering of “patches” of stems best approximates the fate of genetic individuals. Population size is likely to be underestimated because more than one genotype can sometimes occur in a patch. The number of patches detected at a site in Kansas has greatly increased over the last 11 y since marking locations of individual patches allowed detection of nonflowering stems in subsequent years. The A. meadii population at our site (managed by biennial dormant-season burning) often had more flowering ramets and produced more mature follicles in years with burning. High rainfall in the preceding year, in conjunction with burning, was associated with the highest follicle production. The difficulties in detection of plants at the site mean that counts of numbers of patches over an 11-y period cannot be used to assess whether the population is increasing, decreasing or remaining constant. Several factors indicate a positive outlook for the population: management (burning) enhances fruit production, patch survivorship is high and a likelihood that more patches exist than are counted. However, the low fruit production in most years at the site is a concern for the long-term viability of the population.