Answers to Student Handout Questions (Monarch Butterfly
Controversy Case Study)
1. Research and find the data for these items below.
a. Amount of toxin expressed in the pollen of event 176 andÝ
A: (1.1-7.1 µg/gm pollen)
b. The amount of toxin needed to kill or significantly harm the development of the insect.
A:Ý Depends on the Bt event and the number of pollen grains monarch larva consume.Ý Generally event 176 expresses higher amount of protein per pollen grain as compared to other events, so less consumption is needed to effect larva.
Information for all events found in the Assessing the impact of Cry1Ab-expressing corn pollen on monarch butterfly larvae in field studies paper.
c. What is the likely-hood that a monarch larva will come in contact with the toxin.
A:Ý Taken from PNAS paper Temporal and spatial overlap between monarch larvae and corn pollenÖ.. Results presented here have two important implications. First, a portion of the monarch population is exposed to and probably consumes corn pollen that collects on milkweed plants growing in cornfields. Recent research suggests that the Bt corn hybrids most commonly planted produce levels of toxin in their pollen that are unlikely to have severe fitness consequences on monarchs (22-24), but our findings indicate the need to evaluate future transgenic hybrids on the basis of their protein toxicity and expression in pollen. Second, regardless of risks imposed by transgenic corn, changes in agricultural practices such as weed control or the use of foliar insecticides could have large impacts on monarchs by affecting milkweed density and condition, or monarch survival.
d. The amount of Bt corn pollen found at the different distances from the field.
A:Ý The level of Bt corn pollen collected in tests dramatically decreased 5 meters away from fields, suggesting that pollen will not collect on most milkweed at levels toxic to monarch.
e. Information about mortality of the Monarch (all the ways monarchs die naturally by percentage monarchs die) expressed in a life-table.Ý Is this information available?Ý Is it needed to determine the risk to the monarch butterfly?
A:Ý No comprehensive life tables exist for the monarch butterfly.Ý Is this information needed to assess the risk to the monarch.Ý No, because the data gathered from tests shows that risk of exposure to Bt corn pollen is low for most
monarchs.Ý Life-tables would shed light on the overall mortality rate and how bt toxin exposure resulted death fits into the overall mortality as a percentage.Ý
2. What is the risk to the monarch butterfly from Bt corn?Ý
a. Do we have enough data?
b. Do we need all possible data to access the risk?
A:ÝÝ No, enough data exists to determine risk
c. Identify what the risk is to the monarch butterfly?
A:Ý Generally the risk is low, however Bt events such as 176 that express greater level of toxins per pollen weight pose the greatest risk of all types tested.
3. After analyzing the data in the readings, what do you think the impact is to population from Bt crops?Ý Are there greater risks to Monarch butterflies other than Bt crops?Ý Justify your answer.ÝÝÝ
A:Ý Impact on the monarch is low.Ý
A:Ý Yes, there probably are greater risks to monarchs than Bt corn pollen, i.e. habitat destruction, agriculture practices, cars hitting monarchs on the highway etc.Ý
4. Are there other insects that can be found in and around a corn field that may be harmed by Bt crops engineered to kill European Corn Borers?Ý List some examples.
A:Ý Black swallowtails, tiger moths, other butterfly or moths
5.Ý If there are other insects that are at risk from Bt exposure, why do you think Losey chose to focus his work on the monarch butterfly?
A:Ý Open to interpretation, however it should be noted the monarch butterfly is perhaps the best known and loved of all insects.Ý Any newly discovered hazard would be big news and be of interest to both the press and public.