Bees--and other pollinators--gravitate toward the enticing aroma of the milkweed, too.
The milkweed is widely known as the larval host plant of the monarch butterflies--and a nectar source for the adults--but they have to share.
The broadleaf milkweed, Asclepias speciosa, in our pollinator garden draws everything from honey bees to leafcutter bees to carpenter bees.
It's almost like "Take a number." And it's especially noticeable during National Pollinator Week, a week set aside to celebrate the pollinators and to do what we can to protect them.
Recent visitors to the milkweed have included:
- A male Valley carpenter bee, Xylocopa varipuncta, a green-eyed blond
- A female Valley carpenter bee, Xylocopa varipuncta, solid black
- Honey bee, Apis mellifera
- Male leafcutter bee, Megachile sp.
And, of course, the monarchs (Danaus plexippus)!
From her post at Texas A&M University, located at College Station, 90 miles northwest of Houston, Christine Merlin basically has a front-row seat for the monarch butterfly migration.
She sees them heading to Mexico to overwinter, and she sees them returning.
But it's the science that drives her.
Merlin, an assistant professor in the Department of Biology, will speak on "The Monarch Butterfly Circadian Clock: from Clockwork Mechanisms to Control of Seasonal Migration" from 12:10 to 1 p.m., Wednesday, June 1 in Room 230 of Wellman Hall.
The seminar, sponsored by the UC Davis Department of Entomology and Nematology, will be hosted by assistant professor Joanna Chiu. It is open to all interested persons. Plans are to record it for later posting on UCTV.
"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 photo period-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."
"I will discuss progress that our lab has made in developing reverse-genetics in the monarch butterfly to unlock its potential as a genetic model system to study animal clockwork mechanisms and the involvement of the circadian clock in insect photoperiodic responses," she says. "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."
In a Texas A&M news story, Vimal Patel described her as trying to unravel "the mysteries of the migration and the role of internal clocks in the process."
"It's incredible how such a fragile insect can complete a long-range migration so demanding," Merlin told Patel. "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 points out that "Migration begins every year in the fall, when the day lengths change. 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.
Good news: The first day of spring.
Bad news: The future of the Eastern, migratory population of the monarch butterflies.
Research published today in Scientific Reports indicates there's a "quasi-extinction risk" for the Eastern, migratory population of monarch butterflies (Danaus plexippus).
A nine-member team, led by Brice X. Semmens of the Scripps Institution of Oceanography, UC San Diego, noted that the Eastern, migratory population has declined by more than 80 percent over the last decade. "The monarch's multi-generational migration between overwintering grounds in central Mexico and the summer breeding grounds in the northern U.S. and southern Canada is celebrated in all three countries and creates shared management responsibilities across North America," they wrote in their abstract.
"...We find that, given a range of plausible quasi-extinction thresholds, the population has a substantial probability of quasi-extinction, from 11–57 percent over 20 years, although uncertainty in these estimates is large."
The world population of monarchs dipped from 1 billion in the mid-1990s to about 150 million monarchs today, estimates show. The authors noted that "the vast majority of the remaining monarchs live in the eastern portions of Canada, the United States and Mexico."
The researchers blamed the loss of breeding habitat as the major cause for the decrease in the United States.
Monarch lay their eggs only on milkweed, and caterpillars eat only milkweed. Other threats: habitat loss in the Mexican overwintering sites, climate change, insecticides, mowing regimes, invasive species, and diseases.
What to do? There's a movement afoot to place the monarch on the Fish and Wildlife Service's threatened or endangered species list.
Meanwhile, the key solution is to create and restore monarch breeding habitat, the researchers said.
It would be a shame to lose the mighty monarch.
Last December the Xerces Society for Invertebrate Conservation released preliminary figures. Now they've announced the final tally: almost 272,000 monarchs (Danaus plexippus).
The good news is that it's a little up from last year. Yes! But the not-so-good news is that the total is 39 percent lower than the long-term average.
The Xerces Society has sponsored and spearheaded the count since 1997. The project spans 16 counties along the California coast. It's called the “Thanksgiving Count” but it's a three-week project centered around the holiday. Who surveys them? Volunteers. It's a massive and important endeavor.
"Results from a survey of monarch butterfly overwintering sites in California show that there are more monarchs overwintering in the state this year than last," wrote Sarina Jepsen, director of Xerces Endangered Species Program, and Scott Hoffman Black, Xerces executive director, on their website. "Volunteers with the Xerces Society's Western Monarch Thanksgiving Count visited 187 sites and tallied a total of 271,924 monarchs. Although more monarchs were counted, the average number of monarchs per site is not significantly different than last year's count, and this year's population estimate represents a 39% decline from the long term average. The number of monarchs counted this year is but a fraction of the 1.2 million monarchs recorded in the late 90s."
They noted some promising data. "Fifteen sites that have been continuously monitored had the highest numbers of butterflies in a decade. Several sites that had not seen monarchs for years were occupied, and there were a number of sites, such as the Berkeley Aquatic Park, that hosted overwintering monarchs for the first time. In Marin County in the northern extent of the overwintering range, 11 sites had increased numbers and two new sites each supported more than 8,000 butterflies."
Unfortunately, the sites surveyed in southern California showed fewer monarchs than last year.
Xerces is working feverishly to save the monarchs and is encouraging others to do so, too. “The monarch butterfly population has recently declined to dangerously low levels,” Xerces wrote on their website. “In the 1990s, estimates of up to one billion monarchs made the epic flight each fall from the northern plains of the U.S. and Canada to sites in the oyamel fir forests north of Mexico City, and more than one million monarchs overwintered in forested groves on the California Coast. Now, researchers and citizen scientists estimate that only about 56.5 million monarchs remain, representing a decline of more than 80% from the 21 year average across North America.”
Personally, we were delighted to see monarchs overwintering in the Berkeley Aquatic Park and the gathering--though sparse--near St. Peter's Chapel on the Mare Island Naval Shipyard, Vallejo, Solano County. Monarchs used to overwinter in the eucalyptus trees near the Solano County Juvenile Hall, Fairfield, but someone felled the trees.
Meanwhile, what can we do to conserve the monarchs? Xerces lists these excellent points:
- Plant native milkweed and nectar plants. Find sources of local, native milkweed seed in your state using our Milkweed Seed Finder.
- Learn more about growing milkweeds on our Project Milkweed page.
- Avoid using insecticides and herbicides.
- Support agriculture that is organic or free of Genetically Modified ingredients.
- Become a citizen scientist and contribute to research efforts to track the monarch population in its breeding and overwintering range.
- Support the Xerces Society's monarch conservation efforts
Another thing we can do is become "Monarch Moms" and "Monarch Dads." Rear them for conservation purposes. Then release them and watch them soar. It's a feeling like no other. If you look on Facebook, you can network with the Monarch Moms and Monarch Dads out there.
The Beautiful Monarch
Public group administered by Holli Webb Hearn
"The Beautiful Monarch group was created to teach members how to raise and properly care for the monarch butterfly from egg to flying adult along with learning about their predators, diseases and other monarch facts. It is my hope that as a collective group we will help and teach one another along with any new members that join us."
Raising Butterflies and Moths for Conservation (+All Pollinators)
Closed group monitored by Mona L. Miller (apply to join)
"Our focus is the preservation and protection of North American butterflies, moths and pollinators, particularly the Monarch Butterfly."
There's even a Monarch Teacher Network. (Teaching and Learning with Monarch Butterflies)
The more we know about monarch butterflies, the better we can understand them and help conserve them.
Newly published research on California's overwintering monarch butterflies (Danaus plexippus) confirmed many previous migratory studies, but found some unexpected and surprising patterns of movement, said lead researcher Louie Yang, a community ecologist with the UC Davis Department of Entomology and Nematology.
The study, “Intra-Population Variation in the Natal Origins and Wing Morphology of Overwintering Western Monarch Butterflies (Danaus plexippus)," published in the early online version of the journal Ecography, examined the natal origins, or “birthplaces,” of butterflies at four California overwintering sites.
It will be incorporated into an online issue, perhaps within six months, but it has not yet been assigned to an issue, said journal managing editor Maria Persson.
Natal origins of butterflies collected from the two northern sites--Lighthouse Field State Beach and Moran Lake, both in Santa Cruz County--varied significantly from those collected at the two southern overwintering sites--Pismo State Beach, San Luis Obispo County; and the Coronado Butterfly Preserve, Santa Barbara County, they said.
“We hope that this paper improves our understanding of where monarch butterflies grow up in western North America,” said Yang, an associate professor. “This study uses a naturally occurring continental-scale pattern of hydrogen isotopes in precipitation in order to estimate the natal origins of overwintering butterflies. Building a clearer understanding of where they come from could help us better understand many aspects of their ecology.”
The research is the work of Yang; Dmitry Ostrovsky of the University of Colorado, Denver; and Matthew Rogers and Jeffery Welker of the University of Alaska.
The research team set out to answer two key questions: “How do broad geographic areas of potential natal habitat contribute to the overwintering population of western monarch butterflies in California?” and “How does the individual variation in the wing morphology of overwintering western monarch butterflies correlate with estimated migratory distance from their natal origins?”
They first compared the wings of 114 monarch butterflies collected from the four overwintering sites with a continental-scale monarch butterfly wing isoscape derived from the U.S. Network for Isotypes in Precipitation (USNIP) database. They used spatial analyses of stable isotype ratios and correlations with wing morphology. Then they examined the correlations of monarch butterfly forewing size and shape.
Of the 114 butterflies sampled, they found that 30 percent developed in the southern coastal range; 12 percent in the northern coast and inland range; 16 percent in the central range, and 40 percent developed in the northern inland range.
“Interestingly, the two most northern overwintering sites in the study showed the largest contributions from the southern coastal range (Lighthouse Field, 45 percent; Moran Lake, 37 percent; Pismo Beach, 22 percent; and Coronado Preserve, 24 percent) while the two most southern overwintering sites showed the largest contributions from the northern inland range (Lighthouse Field, 30 percent; Moran Lake, 35 percent; Pismo Beach, 53 percent; and Coronado Reserve, 39 percent),” they wrote.
The researchers randomly collected the monarchs Dec. 4-6, 2009 from aggregations in trees. The collecting resulted in: 19 males and 9 females from Coronado; 22 males and 8 females from Pismo State Beach; 20 males and 10 females from Moran Lake; and 18 males and 8 females from the Lighthouse Field State Beach.
In addition, the male monarch butterflies showed mean total masses that were 5.8 percent larger than those of the females.
The monarch butterfly of North America overwinters along the California coast and in the central mountains of Mexico. Previous studies have indicated that the western monarchs or those from natal habitats west of the Rocky Mountains, overwinter along the California coast. Those that develop east of the Rockies overwinter in central Mexico.
The project was funded in part by a National Science Foundation (NSF) Early Career Development Program grant awarded to Louie Yang, and a NSF Major Research Instrumentation Program grant awarded to Jeffrey Welker.