Soil Conditions of Asclepias asperula and Asclepias viridis in South Central Texas for Monarch Butterfly (Danaus plexippus) Conservation
The decline in Danaus plexippus (monarch butterfly) populations has led to increased interests in their habitat conservation and importance of milkweed (Asclepiadaceae). Soil conditions that promote the growth of Asclepias asperula and Asclepias viridis in Texas are largely unknown. This study evaluated the parameters for the bulk soil (1 m) and rhizosphere (20 cm) from areas where A. asperula and A. viridis were found and adjacent areas where they were absent at four sites in Texas. Organic matter, nitrate, phosphate, texture, bulk density, porosity, pH, and electrical conductivity (EC) were compared. No significant differences occurred between rhizosphere and bulk soils of milkweed in any of the parameters measured ( p > 0.05). However, there were differences in conditions based on site (p < 0.05) for clay content, EC, organic matter, and phosphate. There was a strong influence of textural classification on soil properties (p < 0.05). Together, these results suggest that A. asperula and A. viridis are not necessarily habitat specialists based on the parameters analyzed.