Evaluation of milkweed (Asclepias spp.) restoration in the Rolling Plains ecoregion of West Texas for the enhancement of monarch butterfly (Danaus plexippus) habitat

The monarch butterfly (Danaus plexippus) is among the best-known insects in the world, renowned for its conspicuousness, spectacular migration, and interesting biology. Unfortunately, monarch populations have declined dramatically due, in large part, to the widespread losses of the milkweed plants which they depend upon for reproduction. This has led to concerted efforts to restore milkweed, particularly in the Midwestern US where most monarch breeding occurs. However, recently there has been a call to expand milkweed restoration across more of the monarch’s migratory distribution, with Southern states, like Texas, being emphasized. In this study, we evaluated the feasibility of milkweed restoration in the Rolling Plains ecoregion of West Texas, an area with numerous reports of monarchs but relatively limited conservation initiatives. We founded milkweed colonies that included four species of milkweed in three counties across West Texas, and the establishment and growth of milkweed in these was monitored for up to four years. Generalized additive mixed-effect models were then used to assess milkweed establishment and growth as a factor of plant age, species, and location. Temporal patterns in establishment and growth were also examined. Milkweed were successfully established across all colonies and as many as 45% of some species persisted four years after being planted. Additionally, we found age (p < 0.001), species (p = 0.02), and location (p = 0.04) to be significant predictors of establishment, while species was a significant predictor of growth (p = 0.001). While more research is needed to assess the restoration of milkweed in West Texas, this is, to our knowledge, the first study to monitor milkweed over an entire season in this area and may provide valuable data to facilitate development of a regionally adapted milkweed restoration strategy.