The eastern population of monarch butterflies has declined significantly during the past 20 years. As the figure here illustrates, Iowa is in the heart of the summer breeding range for these monarchs. Habitat restoration that includes planting native milkweed species is critical for monarch conservation.
Recent research by Iowa State University graduate student Victoria Pocius took a closer look at larval performance and survival on nine milkweed species native to Iowa.
"We examined the development and survival of monarchs from first-instar larval stages to adulthood," says Pocius, graduate research assistant in the Ecology and Evolutionary Biology program at ISU.
The study included the following native species of milkweed:
- Common milkweed (Asclepias syriaca)
- Swamp milkweed (A. incarnata)
- Butterfly milkweed (A. tuberosa)
- Whorled milkweed (A. verticillata)
- Showy milkweed (A. speciosa)
- Poke milkweed (A. exaltata)
- Prairie milkweed (A. sullivantii)
- Tall green milkweed (A. hirtella)
- Honeyvine milkweed (Cynanchum laeve)
Milkweeds in the genus Asclepias and Cynanchum are the only host plants for larval monarch butterflies in North America, but data regarding larval performance and survival across nine milkweeds native to the Midwest is limited. Results from this greenhouse experiment indicate that monarch butterflies can survive on all nine milkweed species, but the expected survival probability varied from 30 to 75% among the nine milkweed species.
"Monarch larvae will consume all nine milkweed species tested, but survivorship varies across the species," says Pocius. "Understanding how milkweed species influence monarch development and survival is critical in choosing milkweed species for monarch habitat restoration."
Research results show that seven of the nine species could be used for monarch habitat restoration in the Midwest assuming that each species is planted within its native range and in its appropriate habitat. Findings from this study also suggest that A. hirtella and A. sullivantii are not the best choice for monarch habitat plantings because larvae had a lower probability of reaching adulthood. Specifically, only 30% of larvae that fed on A. hirtella and 36% that fed on A. sullivantii reached adulthood compared with 75% that fed on A. tuberosa and 72% that fed on A. exaltata.
More information about this study is available in the recent issue of Environmental Entomology.
This work was partially funded by the USDA National Institute of Food and Agriculture, Hatch project number 1009926 (IOW05478) and by the USDA, Natural Resources Conservation Service’s Conservation Innovation Grant program under Agreement Number 69-3A75-16-006. Additional support was provided by Prairie Biotics Inc. and the Iowa Monarch Conservation Consortium.