The Monarch Butterfly: A Journey of Flight and Evolution

By Jessica Williams

Education Coordinator, Keystone Wildlife Coalition

In this edition of the Keystone Wildlife Coalition Newsletter we explore the monarch butterfly as a flagship species. A flagship species is one that is used to promote conservation efforts and raise awareness due to its charisma or appeal. These species often symbolize larger environmental issues. Keystone species are defined by their ecological function, while flagship species are defined by their symbolic importance. Keystone species directly influence biodiversity through their roles, whereas flagship species primarily serve to highlight the need for conservation efforts, which can indirectly benefit biodiversity. Both types of species are important in conservation, but they serve different purposes in ecological studies and public awareness.

The monarch butterfly (Danaus plexippus) is renowned for its vibrant orange and black wings and awe-inspiring migration across North America. Millions of butterflies  migrate from Mexico to Canada every year, covering thousands of miles. Recent scientific studies have revealed fascinating insights into the genetic and evolutionary mechanisms behind their migration, coloration, and adaptation to toxic diets.

Genetic Secrets Behind Migration

A groundbreaking study published on October 1, 2024, in Nature by a team led by Marcus Kronforst from the University of Chicago has shed light on the genetic basis of monarch migration. By sequencing the genomes of 101 butterflies from various regions, researchers identified a key gene associated with migratory behavior. This gene, involved in flight muscle formation, was highly expressed in migratory monarchs, enabling them to fly long distances more efficiently than their non-migratory counterparts. Migratory butterflies exhibited reduced oxygen consumption and lower flight metabolic rates, enhancing their endurance for the epic journey from Mexico to Canada.

Coloration and Adaptation

In addition to migration, the study explored the genetic underpinnings of monarch coloration. Monarchs are known for their distinctive orange and black wings, which warn predators about their toxicity. A small percentage of monarchs, particularly in Hawaii, display white wings. Researchers discovered that a single gene coding for a myosin motor protein functions as a pigmentation switch. This gene mutation disrupts pigment transport to the wings, resulting in the white coloration observed in some butterflies. This finding represents a new genetic pathway in insect coloration, comparable to similar processes observed in mice.

Immune to Toxicity

Another aspect of monarch adaptation involves their immunity to the toxins in milkweed, the plant on which they feed. Two independent research teams have identified three genetic mutations that confer this immunity. By using gene-editing tools like CRISPR, scientists were able to recreate these mutations in fruit flies, demonstrating how these changes allow monarchs to tolerate and even retain the toxins from their diet. This adaptation is crucial for the butterflies' survival, as it deters predators and supports their migratory lifestyle.

Current Threats and Conservation

Despite their iconic status, monarch butterflies face significant threats, including habitat loss due to agricultural practices and climate change. The decline in milkweed, essential for their larval development, has exacerbated their population decline. Conservation efforts are crucial to preserving their migratory routes and habitats.

In Conclusion 

The journey of the monarch butterfly highlights the urgent need for conservation. Despite facing threats like habitat loss and climate change, we can make a difference. Supporting conservation efforts is crucial to protecting these butterflies and their ecosystems. If you'd like to help, consider donating to the Keystone Wildlife Coalition. Your support can aid in preserving the habitats essential for monarchs. Donate today at Keystone Wildlife Coalition.

Concise Timeline

• More than 1 million years ago: Monarch butterflies are believed to have originated from an ancestral migratory population in Africa, gradually spreading to the Americas. This migration set the stage for their future extensive northward journeys.

• Twenty thousand years ago: Following the end of the last ice age, monarchs began expanding their range northwards. They adapted to new environments and established their current migratory patterns across North America.

• 1990s: The eastern North American monarch population was approximately 1 billion butterflies. This large population utilized expansive milkweed habitats across the U.S. and Canada for breeding and migration.

• 2000s: Researchers began observing signs of population decline due to habitat loss and environmental changes. Efforts to understand the reasons behind this decline intensified.

• 2014: Significant conservation concerns emerged as the monarch population in Mexico's overwintering sites dropped to around 1.65 acres. This decrease raised alarms about the impacts of habitat loss and climate change.

• 2021: The eastern monarch population had fallen dramatically to only 5 acres in their overwintering forests in Mexico, representing a decline of over 90% from historical levels. This dramatic drop underscored the urgent need for conservation efforts.

• 2022: The western North American monarch population was estimated to be around 250,000, down from 1.2 million butterflies in the 1990s. This decline highlighted the broader trends of decreasing monarch populations across their range.

• 2024: Recent studies in Nature and eLife have revealed critical genetic insights into monarch migration and coloration. These findings include the identification of genes responsible for migration efficiency and pigmentation, furthering our understanding of monarch biology and evolution.

Key Terms & Concepts

1. Gene:

   • A gene is a set of instructions in your body that tells it how to grow and function. Think of it as a recipe that decides how something will look or work.

2. Migration:

   • Migration is when animals move from one place to another, often for a long distance, to find food or better living conditions. Monarch butterflies migrate from Mexico to Canada and back every year.

3. Collagen:

   • Collagen is a protein (a kind of molecule) that helps build muscles and other tissues in the body. For monarch butterflies, a gene related to collagen helps them fly long distances without getting too tired.

4. Amino Acids:

   • Amino acids are the building blocks of proteins. Just like different LEGO pieces can build different things, different amino acids build different proteins.

5. Pigmentation:

   • Pigmentation is the process that gives animals and plants their color. For monarch butterflies, a gene controls their orange and black coloring.

6. Diapause:

   • Diapause is a deep sleep that some animals go into to survive harsh conditions, such as winter. Diapause is similar to hibernation. Monarch butterflies use diapause to rest and survive the winter in Mexico.

7. CRISPR:

   • CRISPR is a tool scientists use to change DNA,  similar to editing a document on a computer. It helps them make specific changes to an organism's genes.

8. Cardiac Glycosides:

   • Cardiac glycosides are toxic chemicals found in milkweed plants. If eaten, they can make insects or animals sick. Monarch butterflies have special adaptations that make them immune to these toxins.

9. Metabolic Rate:

   • The metabolic rate is how quickly an animal uses energy. A low metabolic rate means the animal uses energy slowly, which helps it fly long distances without getting tired.

10. Evolutionary Origins:

    • Evolutionary origins refer to where an organism's ancestors came from and how they changed over time to become what they are today.

11. Genetic Blueprint:

    • A genetic blueprint is like a map or a set of instructions in an organism's DNA that guides its development and characteristics.

Sources

1. Kronforst, M. (2024, October 1). The study sheds light on evolutionary origins and the genes central to migration. Nature. Retrieved from [Nature website]

2. Whiteman, N. (2024, September 27). Monarch butterflies and their genetic immunity to milkweed toxins. Nature. Retrieved from [Nature website]

3. Kronforst, M. (2024, September 11). Monarch butterflies owe their long-distance migrations to one gene honed for efficient flight. National Geographic. Retrieved from [National Geographic website]

4. Robles Gil, P. (2024). Monarch Butterfly Biosphere Reserve, Michoacan, Mexico. Retrieved from [Minden Pictures website]

5. Natural History of Monarch Butterfly. (2024). Danaus plexippus plexippus: Description, habitat, migration, and threats. Retrieved from [Natural History website]

6. Zhan, S. (2024, August 27). Genetics of monarch butterfly migration and warning coloration. eLife. Retrieved from [eLife website]

7. Brower, A. (2024, August 15). Monarch butterflies: Migration, muscle efficiency, and genetic findings. Journal of Evolutionary Biology. Retrieved from [Journal of Evolutionary Biology website]

8. Common Butterfly Species in the United States - Rooted Wings Co. https://rootedwingsco.com/common-butterfly-species-in-the-united-states/