Management and Restoration Ecology of the Federal Threatened Mead's Milkweed, Asclepias meadii (Asclepiadaceae)

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Abstract
The federal threatened Asclepias meadii Torr. (Asclepiadaceae) is a perennial, self-incompatible prairie forb imperiled by habitat destruction and population fragmentation. Many large populations persist in prairie 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 species.This study was conducted to determine habitat differences among populations, to understand how hay mowing and lire management affect the structure of A. meadii populations, and to test the effects of different management treatments on restoration of this species. Soils analysis showed a geographic gradient, with southern populations on acid, nutrient-poor soils, and northern populations on calcareous, nutrient-rich soils. Milkweed ramet densities were lower in fire-managed prairies than in haymeadows; but burned sites had 68% flowering ramets while haymeadows 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 toward 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 experiments. competition from oats significantly reduced seedling growth, with greater growth in artificially outcrossed seedlings. At seven restoration 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 vulnerable to drought, with greater survivorship when rainfall was 200% of normal. Planted juvenile mill;weeds had greater survivorship than seedlings, 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. Continued work is needed to determine if restored populations can become viable, and if there are negative effects of crossing and translocating genotypes.