Final answer:
Milkweed attracts monarch butterflies by producing a poison that caterpillars ingest to deter predation and provides nectar for adult butterflies. This relationship emphasizes the need for conservation of milkweed to protect monarch populations.
Step-by-step explanation:
Milkweed's strategy for attracting monarch butterflies primarily involves the production of a chemical that the monarch caterpillars can ingest. Although the milkweed plant is grazed by these caterpillars and gains nothing in this interaction, the monarch caterpillars acquire a poison that deters predation. This toxic substance makes the monarch less appealing to predators, ensuring the survival of the caterpillars and subsequent generations of monarch butterflies.
Aside from providing a chemical defense for monarchs, milkweed also offers nectar that adult butterflies feed on. The relationship between milkweed and monarch butterflies highlights the importance of preserving milkweed plants to maintain healthy monarch populations, especially considering threats such as the use of glyphosate on genetically engineered (GE) crops, which can reduce the availability of milkweed in agricultural areas.
It should also be noted that the NASEM's GE Crop Report identified milkweed as a critical component of the monarch butterfly's lifecycle and called for more studies to assess the impact of agricultural practices on monarch populations. Conservation efforts are therefore directed at protecting milkweed to support these iconic butterflies.