- Author: Kathy Keatley Garvey
The article, “Complexity, Humility and Action: A Current Perspective on Monarchs in Western North America,” is “meant to provide a concise review of and perspective on recent western monarch research,” Yang said.
The western monarch population overwinters along the California coast. Estimated at 4.5 million in the 1980s, it has dropped significantly over the past five years, the professor related, noting an “86% single-year population decline in 2018, an overwintering population of less than 2000 butterflies in 2020, and an unexpected >100-fold increase in 2021."
Yang defined the western monarch population as occupying "a geographically distinct region of North America west of the Rocky Mountain...Ongoing climate change has made the western monarch range warmer, drier, and more prone to heatwaves, wildfires, and winter storms with complex effects on their ecology. Land development and changes in the structure of landscape mosaics have modified both the breeding and overwintering habitats of western monarch butterflies, changing the spatial distribution of resources and risks across their range. Shifts in agricultural and horticultural practice have changed the nature of potentially deleterious chemicals in the environment, including novel herbicides and insecticides."
Yang said the spread of non-native milkweed species has likely had both positive and negative consequences for western monarchs, and more research is needed.
His three suggestions:
- "First, we should continue to support both basic and applied monarch research. This includes efforts to better understand fundamental aspects of monarch biology, studies to examine the ecological factors that limit monarch populations in the West and efforts to improve more targeted adaptive management and monitoring efforts. Basic research in monarch biology and ecology improves our understanding of this complex system and can inform conservation actions in profound and unexpected ways. In turn, applied research can address recognized gaps in knowledge that would otherwise limit available strategies for conservation planning and management."
- "Second, recognizing the limits of our current understanding, we should follow the precautionary principle to minimize the risk of counterproductive action. The complexity of this system makes it difficult to anticipate or assume future changes in behavior, species interactions or population dynamics. In practice, this may mean prioritizing efforts to better understand and facilitate existing mechanisms of ecological resilience and recovery over direct actions to manipulate or augment the population with less certain consequences. More broadly, this approach would probably emphasize common sense approaches to mitigate the widely recognized upstream drivers of global change (e.g., climate change and land use change), rather than those requiring a detailed understanding of their complex, interactive effects on species-specific ecologies further downstream."
- "Third, we should work to improve, protect and maintain the resources required throughout the complex monarch life cycle. In part, this likely means prioritizing conservation efforts that target the times and places that are likely to have the greatest positive effects, building on the common ground of available science. In the case of western monarchs, this includes protecting current and future overwintering habitats, the resources required for population expansion in the early season, and the resources required for the fall migration. Recognizing the potentially widespread and pervasive effects of pesticides, this could also mean efforts to develop more ecologically realistic and relevant metrics for the regulation of environmental chemicals."
Yang opined that "In the broader context, many of the drivers that are contributing to western monarch population declines are likely to also be affecting other species. In turn, many of the strategies that would support monarch conservation would likely benefit other species, and many of the strategies that would benefit other species are likely to also support monarch conservation. As we build on currently available science to better understand and protect the western monarch population, it is imperative that we continue to grapple with the inherent complexity of this system and respond with appropriate humility and necessary action."
Among the 54 scientific publications that Yang referenced was a research article co-authored by UC Davis Distinguished Professor Art Shapiro, who has studied butterfly populations in Central California since 1972. The article, "Fewer Butterflies Seen by Community Scientists across the Warming and Drying Landscapes of the American West," published in Science in March 2021, covered data from the Shapiro transect, the North American Butterfly Association (NABA) community count data and the iNaturalist community observation data. The study observed widespread declines across 450 butterfly species, including the monarch butterfly, in the American West. The authors estimated a 1.6 percent decrease in overall butterfly abundance each year over a 42-year period from 1977 to 2018.
Editors of the journal, Current Opinion in Insect Science, describe it as "a new systematic review journal that aims to provide specialists with a unique and educational platform to keep up–to–date with the expanding volume of information published in the field of insect science."
Yang's research is supported by a National Science Foundation award. He was a guest on National Public Radio's Science Friday in February 2022. Listen to the interview here.
- Author: Kathy Keatley Garvey
The seminar, sponsored by the UC Davis Department of Entomology and Nematology, will be hosted by assistant professor Joanna Chiu.
Merlin joined Texas A&M's Department of Biology in the fall of 2013 and is a member of the Center for Biological Clocks Research.
The eastern North American monarch butterfly (Danaus plexippus) has emerged as a powerful model system to study animal circadian clocks and their role in an unconventional output, the photoperiod-induced long-distance migration," Merlin says in her abstract.
"Circadian clocks are endogenous 24-hour timekeepers that coordinate nearly all of the animal physiology and behavior to its environment to tune specific activities at the most advantageous time of the day. Monarchs use a circadian clock to navigate to their overwintering sites during their seasonal long-distance migration. The clock time-compensates for the movement of the sun across the sky over the course of the day and regulates the sun compass output in the brain. Circadian clocks could also be used to time the monarch seasonal departure from their breeding grounds, and consequently regulate the genetic/epigenetic program controlling migratory physiology and behavior."
In a news story written by Vimal Patel of the Texas A&M communications office, Merlin is described as zeroing in on "unraveling the mysteries of the migration and the role of internal clocks in the process."
Merlin was quoted as saying: "It's incredible how such a fragile insect can complete a long-range migration so demanding. Every piece of it fascinates me, from how it occurs to why they go precisely where they go."
An excerpt from Patel's piece:
"While she was a postdoctoral researcher at the University of Massachusetts Medical School in the laboratory of Prof. Steven Reppert, Merlin and colleagues showed that the clocks necessary for flight orientation lie in the creatures' antennae -- a departure from the previous conventional wisdom that the brain controlled the mechanism, given that it controls behavioral rhythmicity in virtually every other animal, including humans.
"The conclusion stemmed from Merlin's and her co-workers' collective curiosity concerning a decades-old anecdote. Around 50 years ago, entomologist Fred Urquhart found that Monarchs became disoriented after he clipped off their antennae. Since then, it had remained just a suspicion until the Massachusetts team confirmed it with more rigorous research."
"The team's experiment exploited technology in a way Urquhart, who merely observed the Monarchs in flight, could not at the time. They used a plastic barrel-like device called a Mouritsen-Frost flight simulator in which a butterfly is connected by tungsten wire to an output system that indicates which direction it is flying. The results were clear: The antennae-less Monarchs flew in every which direction, while those with intact antennae flew southwesterly, the migratory direction."
Merlin says she's interested in the role of the circadian clock in the induction of the migration. "Migration begins every year in the fall, when the day lengths change," she says. "The shortened day lengths might be a cue for the monarchs to start their migration. And if we can show this is the case and that the circadian clock is involved, we can now start to understand the genetic program that is allowing the migratory behavior."
A native of France, Merlin received her bachelor's, master's and doctoral degrees majoring in animal biology, invertebrate physiology and insect physiology, respectively, at the University Paris 6 Pierre and Marie Curie in France. She accepted a postdoctoral fellowship at the University of Massachusetts in 2007.
Related Links:
- Christine Merlin Lab
- A recent story involved Merlin's partnership with the Texas A&M Center for Mathematics and Science Education's Craig Wilson, along with local mayors and resident monarch enthusiasts within the Bryan-College Station community.