MANAGEMENT AND RESTORATION ECOLOGY OF THE FEDERAL THREATENED MEADS MILKWEED, ASCLEPIAS-MEADII (ASCLEPIADACEAE)

The federal threatened Asclepias meadii Torr. (Asclepiadaceae) is a pe rennial, self-incompatible prairie forb imperiled by habitat destructi on and population fragmentation. Many large populations persist in pra irie haymeadows in Kansas and Missouri despite removal of seed pods by annual summer mowing. Only a few small populations remain in Illinois . Iowa, and northern Missouri. Recovery of these small populations and restoration of new populations are recovery objectives for this speci es.This study was conducted to determine habitat differences among pop ulations, to understand how hay mowing and lire management affect the structure of A. meadii populations, and to test the effects of differe nt management treatments on restoration of this species. Soils analysi s showed a geographic gradient, with southern populations on acid, nut rient-poor soils, and northern populations on calcareous, nutrient-ric h soils. Milkweed ramet densities were lower in fire-managed prairies than in haymeadows; but burned sites had 68% flowering ramets while ha ymeadows had only 19% flowering ramets. This suggests that burning has selected for greater resource allocation toward sexual reproduction, while annual hay mowing has selected for greater resource allocation t oward clonal spread. The Morion Arboretum is conducting: experimental restoration of Asciepias meadiii in the eastern part of its range, an objective of Federal Recovery Planning. In greenhouse and garden exper iments. competition from oats significantly reduced seedling growth, w ith greater growth in artificially outcrossed seedlings. At seven rest oration sites in Illinois and northern Indiana. significant variation in milkweed germination. survivorship and growth was caused by weather , differences among sites, and site management. Seedling were vulnerab le to drought, with greater survivorship when rainfall was 200% of nor mal. Planted juvenile mill;weeds had greater survivorship than seedlin gs, and less sensitivity to drought. Greater growth anti survivorship also occurred in burned than in unburned plots at three sites, but not in all life-stages. Propagated plants from Missouri seed sources were larger than Kansas plants in the garden, but not in the field. Contin ued work is needed to determine if restored populations can become via ble, and if there are negative effects of crossing and translocating g enotypes.